Assistive Technology to Improve Collaboration in Children with ASD: State-of-the-Art and Future Challenges in the Smart Products Sector

Within the field of products for autism spectrum disorder, one of the main research areas is focused on the development of assistive technology. Mid and high-tech products integrate interactive and smart functions with multisensory reinforcements, making the user experience more intuitive, adaptable, and dynamic. These products have a very significant impact on improving the skills of children with autism, including collaboration and social skills, which are essential for the integration of these children into society and, therefore, their well-being. This work carried out an exhaustive analysis of the scientific literature, as well as market research and trends, and patent analysis to explore the state-of-the-art of assistive technology and smart products for children with ASD, specifically those aimed at improving social and communication skills. The results show a reduced availability of products that act as facilitators of the special needs of children with ASD, which is even more evident for products aimed at improving collaboration skills. Products that allow the participation of several users simultaneously through multi-user interfaces are required. On top of this, the trend toward virtual environments is leading to a loss of material aspects in the design that are essential for the development of these children.


Introduction
Autism Spectrum Disorder, hereinafter ASD, is a neurological disorder; it encompasses different types of needs, making it difficult to develop product and service solutions that are adaptable to everyone [1]. Autism is characterized by two main signs: (i) restrictive and repetitive patterns of interests, behavior, or activities, and (ii) persistent communication and social interaction difficulties. The areas where they have the most difficulty are social interaction, imagination, and communication. People with ASD tend to isolate themselves and show no interest in others. This is the aspect that most affects their well-being [2]. Their lack of social awareness, as well as their refusal to share, makes collaboration with other children more difficult. These children have difficulties adapting [3][4][5] and developing in collaborative games given their inflexibility and their difficulty predicting responses and identifying the emotions of their partner.
These difficulties have an impact on the deficiencies in interaction, communication, and social imagination [6], essential skills for child independence [5]. In addition to this, they can cause anxiety in children [3,7]. Other indirect impacts such as bullying, social rejection, and school dropout also arise [5]. Therefore, for these children, it is important to acquire collaborative skills that improve their behavior in the social environment in which they live [3].
Due to this challenge, the importance of cooperative play in children with ASD is emphasized. Learning to work together in reciprocity and maintaining joint attention with Records from the Institute for Scientific Information (ISI) Web of Knowledge (WOK) were restricted to the years 2000 to 2022. A total of 1852 records were identified ( Figure  1). In the end, 328 records were included for analysis, integrating scientific articles, books, conferences, theses, and generics. Table 1 shows the statistics of the different types of sources. These records were divided into different categories: 1. Article Reviews: state-of-the-art of medium/high assistive technology tools for children with ASD. 2. Autism (basis): articles dedicated to autism spectrum disorder, focusing on characteristics, symptoms, and needs to be covered with the products. 3. Autism (models and therapies): articles focused on methodologies and therapies focused on the development of skills in children with ASD. This category includes papers that discuss the theoretical framework or propose new therapies. 4. Techniques and tools (basis): articles that describe techniques and tools used to improve the skills of children with ASD. 5. Techniques and tools (case studies): works whose objective is the development of assistive technology that is tested on users. 6. Design Methodologies and Guidelines: works focused on improving the product design process; methodologies, methods, good practices, or assistive technology design guides are proposed. This category is further subdivided into: (1) design methods specialized in ASD, (2) design methods for typical development; and (3) participatory design. In the end, 328 records were included for analysis, integrating scientific articles, books, conferences, theses, and generics. Table 1 shows the statistics of the different types of sources. These records were divided into different categories: 1. Article Reviews: state-of-the-art of medium/high assistive technology tools for children with ASD. 2.
Autism (basis): articles dedicated to autism spectrum disorder, focusing on characteristics, symptoms, and needs to be covered with the products. 3.
Autism (models and therapies): articles focused on methodologies and therapies focused on the development of skills in children with ASD. This category includes papers that discuss the theoretical framework or propose new therapies.

4.
Techniques and tools (basis): articles that describe techniques and tools used to improve the skills of children with ASD.

5.
Techniques and tools (case studies): works whose objective is the development of assistive technology that is tested on users. 6.
Design Methodologies and Guidelines: works focused on improving the product design process; methodologies, methods, good practices, or assistive technology design guides are proposed. This category is further subdivided into: (1) design methods specialized in ASD, (2) design methods for typical development; and (3) participatory design. 7.
Play and Toys: articles related to characteristics and forms of play for children with typical development and ASD, as well as work focused on the study of characteristics and trends of toys for both groups. 8.
Interactive and Smart Design: development of interaction design theory. 9.
COVID19 and Autism: analysis of the impacts of the pandemic and how it has generated new needs for assistive technology products. This last category is included given the number of articles dedicated to the relationship between COVID-19 and its impact on children with ASD during the last two years (2020)(2021)(2022). This selection of articles is considered relevant to the study, as the extreme circumstances of this pandemic have highlighted the importance of assistive technology in the domestic context of children with ASD and their families. Furthermore, the new work and academic models that have been implemented after the pandemic (such as telework or flexible hours in the work environment) have created the need for new strategies to be able to balance work life with family life, thus emerging the need for new assistive technology products focused on these new contexts. Table 2 shows the different categories, as well as the number of records in each category, and the range of dates that are analyzed according to the records found. Of these records, 203 are papers published in scientific journals included in the journal Citation Reports. Table 3 summarizes the nine main journals for the articles included in this work, classified according to the frequency of publication in the following order: "Journal of Autism and Developmental Disorders", indexed in the category of psychology and development within the first quartile (Q1); "International Journal of Social Robotics", is a technical journal indexed in the category of robotics (Q1); and "Research in Autism Spectrum Disorders", "Computers in Human Behavior", "Research in Developmental Disabilities", "Autism" and "Autism Research", indexed in psychology and education in the first quartile (Q1). The journals "Sensors" (engineering and chemistry categories in the second quartile Q2) and "ACM Transactions on Accessible Computing" (computer science category in the fourth quartile Q4) are technical journals. On the other hand, the geographical areas represented in the affiliations of the 319 selected resources, which covered 50 countries, were analyzed. Table 4 shows the most representative. Among them, the United States stands out, representing 31.40% of the resources, followed by the United Kingdom (12.20%) and Spain (9.76%).

Patent Analysis
A patent search and study were conducted using the "WIPO Patent Scope" database between 28 March and 3 April 2022. This search was aimed at collecting patents for smart and interactive assistive technology products aimed at improving the collaboration and social skills of children with ASD. These products were divided into three groups: Virtual Environments, Robots, and Toys. For this search, results were found between April 2007 and March 2022. Table 5 details the searches performed, as well as the number of results obtained. In the end, 55 patents were selected to perform the analysis. areas and fields of the patents, the location of the target area of the applications in the patent consortium, and the details for the evolutionary potential analysis. Although a new code system called CPC (Cooperative Patent Classification) is currently being implemented, it was not used because some of the selected patents were not up to date during the search period. For the analysis and visualization of the results based on IPC codes, the PatentInspiration software was used.

Analysis of Commercial Assistive Technology Products for Collaboration in Children with ASD
AT solutions are marketed primarily outside of information published in research sources, such as scientific journals or conference articles. Therefore, this commercial search strategy was carried out using Google. The search for commercial solutions was carried out between 18 March 2022, and 25 March 2022, to find solutions marketed on the global market, with descriptions available in English.
In the first phase of this section, a search was carried out for companies dedicated to the development of assistive technology for children with ASD. These companies were divided into two groups: (i) companies dedicated to the medium-high assistive technology sector, and (ii) companies in the toy sector. This last category was included because many of the products specialized in ASD currently available on the market are intended for children, so the AT is configured as a toy to enhance the child's attention and improve the acceptability of tasks. The categorization of products from these companies was studied, as well as the offer available for categories related to collaboration.
As a second phase of the commercial analysis, a search was carried out for popular AT products aimed at improving collaboration in children with ASD. About 30 products were selected and divided into three categories: (i) mobile applications and virtual environments, (ii) robots, and (iii) toys. Then, these products were analyzed within the collaboration categories.

Results
This section describes the results of the analysis of assistive technology and interactive and intelligent products, focused on the development of communication skills and social skills of children with ASD, with the objective of analyzing the current situation of scientific literature, patents, and commercialized products.

Literature Review
Currently, 1 in 44 children is diagnosed with ASD, which corresponds to approximately 2.27% of the population [11]. The increase in the number of diagnoses, together with the fact that their origin is unclear in 90% of cases [12], has led to an increase in the number of studies related to autism in recent years, being one of the most studied pathologies in the scientific literature. Figure 2 presents the trend of scientific studies related to autism according to ISI WOK ("AUTISM"), with a total of 75,291 resources in the last 20 years (2012-2022).  Specifically, research related to assistive technology specialized in ASD has increased in the last decade. These studies range from theoretical and analytical studies to technological developments with user validation. For the present work, resources related to the development of interactive and/or intelligent products for the improvement of social and collaborative skills of children with ASD are considered.
The ten most frequent research areas covered by ISI WOK results in the search "COL-LABORATION" AND "CHILDREN" AND "AUTISM", include 590 results, which are classified in Figure 3. Within this classification, the 213 scientific articles related to the objective of the review are indexed in the categories of Journal Citation Report shown in Table 6.  Specifically, research related to assistive technology specialized in ASD has increased in the last decade. These studies range from theoretical and analytical studies to technological developments with user validation. For the present work, resources related to the development of interactive and/or intelligent products for the improvement of social and collaborative skills of children with ASD are considered.
The ten most frequent research areas covered by ISI WOK results in the search "COL-LABORATION" AND "CHILDREN" AND "AUTISM", include 590 results, which are classified in Figure 3.  Specifically, research related to assistive technology specialized in ASD has increased in the last decade. These studies range from theoretical and analytical studies to technological developments with user validation. For the present work, resources related to the development of interactive and/or intelligent products for the improvement of social and collaborative skills of children with ASD are considered.
The ten most frequent research areas covered by ISI WOK results in the search "COL-LABORATION" AND "CHILDREN" AND "AUTISM", include 590 results, which are classified in Figure 3. Within this classification, the 213 scientific articles related to the objective of the review are indexed in the categories of Journal Citation Report shown in Table 6.  Within this classification, the 213 scientific articles related to the objective of the review are indexed in the categories of Journal Citation Report shown in Table 6. By analyzing Figure 3 and Table 6, it can be seen that most of the resources focused on studying the collaboration and social skills of children with ASD, as well as the therapies and tools used to improve them, are found more frequently in the fields of psychology and education. Research is less often related to the technical disciplines of engineering, computer science, or design.
The bibliographic search was analyzed by clustering. The VOS Viewer SW tool was used, which provides visually indicative clusters. Of the 328 resources analyzed, 1179 keywords (659 different) were obtained for which full counting was used. Figure 4 shows the 7 clusters obtained with 87 elements (keywords) and 371 links between keywords (the minimum number of occurrences of a keyword was two):

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Green cluster: groups words related to autism spectrum disorder and intervention and therapy with assistive technology tools. • Blue cluster: collects words related to the epidemiology of autism spectrum disorder and the development of these children.

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Red cluster: groups the words related to autism and its needs for social inclusion. By analyzing Figure 3 and Table 6, it can be seen that most of the resources focused on studying the collaboration and social skills of children with ASD, as well as the therapies and tools used to improve them, are found more frequently in the fields of psychology and education. Research is less often related to the technical disciplines of engineering, computer science, or design.
The bibliographic search was analyzed by clustering. The VOS Viewer SW tool was used, which provides visually indicative clusters. Of the 328 resources analyzed, 1179 keywords (659 different) were obtained for which full counting was used. Figure 4 shows the 7 clusters obtained with 87 elements (keywords) and 371 links between keywords (the minimum number of occurrences of a keyword was two):

•
Green cluster: groups words related to autism spectrum disorder and intervention and therapy with assistive technology tools.

•
Blue cluster: collects words related to the epidemiology of autism spectrum disorder and the development of these children.

•
Red cluster: groups the words related to autism and its needs for social inclusion.

•
Yellow cluster: groups the words related to the COVID-19 pandemic and autism.

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Purple cluster: collects words related to autism spectrum disorder and collaboration between children, parents, and professionals.

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Light blue cluster: refers to words related to toys, autism, and stereotypes.

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Orange cluster: collects words related to the social participation of adolescents. As established in Section 2 "Methods", to structure the review, the set of selected works was classified into nine categories: Article Reviews, Autism (basis), Autism (Models and Therapies), Techniques and Tools (basis), Techniques and Tools (case studies), Design Methodologies and Guidelines, Play and Toys, Interactive and Smart Design, and As established in Section 2 "Methods", to structure the review, the set of selected works was classified into nine categories: Article Reviews, Autism (basis), Autism (Models and Therapies), Techniques and Tools (basis), Techniques and Tools (case studies), Design Methodologies and Guidelines, Play and Toys, Interactive and Smart Design, and COVID19 and Autism. Of the 328 resources analyzed, 248 are specifically dedicated to autism, the rest being resources focused on special needs in general (28), and design articles based on typical development (52). Table 7 shows the number of resources specifically focused on autism for each category. Within these 248 resources focused on autism, 122 are specifically dedicated to collaboration and social skills. These are classified in Table 8. As can be seen, the largest number of articles focused on collaboration and social skills is in the categories of Techniques and Tools (Case Studies with 34.5% and Basis with 18%). Within these categories, the resources found in "Techniques and Tools (basis)" are primarily focused on exploring the potential of assistive technology in social and collaboration skills of children with autism, including and comparing robots, virtual environments, interactive products, and others. These records also discuss the benefits these systems could have in education and classrooms, arguing that the use of these types of products could have very positive effects on the collaborative skills of these children [13][14][15][16][17]. On the other hand, in the category of Techniques and Tools (Case Studies) records are dedicated to testing several AT solutions with children with autism. These solutions include apps, virtual environments, interactive products, robots, and others. Most of the resources in this category were focused on virtual environments. This will be further analyzed in this section. Although the category of Design Methodologies and Guidelines is the second most significant category with 26.4%, most of the studies found in this category (30/32) conceptually describe the importance of participatory design with children with ASD, families, and professionals to obtain efficient AT solutions, however, they do not develop concrete design methods or design processes. On the other hand, the other two resources that do propose specific methods are focused on virtual environments, but no specific methods have been found for other types of high-tech products, such as robots or smart products, nor have they been found for toys. Thus, there is a clear shortage of design methods and tools dedicated to the development of AT products that improve the collaboration and social skills of children with ASD. It is also worth noting the low frequency of publications dealing with collaboration in the category of Play and Toys, and the nonexistence of studies in the categories of Interactive and Smart Design and COVID-19 and Autism. After analyzing in detail this classification, it should be noted that in the first category (Article Reviews), 15 scientific articles and 1 conference article dedicated to the study of the state-of-the-art of interactive and intelligent products were found (see Table 7). However, several of these reviews are of general scope, that is, they are not oriented to any specific product or need [18][19][20]. Other studies look at a particular type of assistive technology, such as virtual environments [21][22][23], or robots [24][25][26][27][28]. Likewise, it is worth noting that the only two review studies whose scope is "collaboration" (see Table 8) are developed by Baykal et al., where the development of social and communication skills in populations with special needs is evaluated [29], and Silva-Calpa et al., with the focus on virtual environments specialized in autism [10]. This work has not found studies in this category that review the current state of development of AT specializing in collaboration and social skills for ASD.
The concept of assistive technology developed in these investigations includes any device, software, or equipment that helps overcome certain challenges that require assistance to perform activities of daily living independently. Specifically, a subclassification can be identified according to the scope of the AT: • Low-tech products: traditional tools and methods that use non-interactive products or do not use energy. • Medium/high technology: with electronic and computerized elements that improve efficiency, speed, and accessibility.
Works with this scope belonged to the following categories: 4. Techniques and tools (basis), 5. Techniques and tools (case studies), and 6. Design Methodologies and Guidelines. Of the 248 resources found, 157 are specialized in ASD: 44 develop AT in general (treat both low and medium/high technology) (28.76%), 3 Low-tech (1.96%), and 106 Mid/high tech (69.28%). These results show the trends of the research effort in the last decade. This situation may be due to the benefits of mid/high-tech AT compared to other types of products [30][31][32].
The resources included in the mid-high tech category were classified into: (1) Virtual environments (mobile applications, video games, virtual and augmented reality environments...), (2) Robots (robots intended for therapy of children with ASD), (3) Interactive products (Toys, wearables), (4) other tools in product form that do not belong to any of the above categories. Figure 5 shows the distribution of the research effort (%) of a total of 106 papers; those works that include in their scope the development of collaboration and social skills in the design of the product are indicated in green. After this analysis and from Figure 5 it can be concluded that most of the assistive technology developed for children with ASD belongs to the category of virtual environments (45.3%), especially those focused on improving the collaboration and social skills of children with ASD (72%). These applications and virtual environments can be very beneficial as they offer great flexibility in content and customization. Highlight the following studies, which demonstrate the potential of such applications in the therapy of children with ASD [2,4,6,14-17,33-36]. However, these types of tools lack tangibility and materiality, aspects especially important for the intuitiveness and stimulation of these users [37,38]. Therefore, it is essential that the research effort is not limited to the study of ex- After this analysis and from Figure 5 it can be concluded that most of the assistive technology developed for children with ASD belongs to the category of virtual environments (45.3%), especially those focused on improving the collaboration and social skills of children with ASD (72%). These applications and virtual environments can be very beneficial as they offer great flexibility in content and customization. Highlight the following studies, which demonstrate the potential of such applications in the therapy of children with ASD [2,4,6,[14][15][16][17][33][34][35][36]. However, these types of tools lack tangibility and materiality, aspects especially important for the intuitiveness and stimulation of these users [37,38]. Therefore, it is essential that the research effort is not limited to the study of exclusively virtual solutions, but combines traditional strategies, methods, and materials with new technologies to develop more complete products (without losing their tangibility and materiality), which are flexible and adaptable to the characteristics of the user.
Second, research focuses on the development of "social robots" (38.7%). Analyzing the publication dates of these works, it is concluded that it is a full development research line, where most of the works aim to demonstrate the benefits offered by the use of robots in therapy for children with ASD [13,24,30,31,[39][40][41][42][43].
The category "smart and interactive products" is the least developed. This category integrates all kinds of interactive and smart products that do not belong to the previous categories, including the AT configured as a toy. This work bases the understanding of toys on Sicart's definition: "a thing at the service of playing and the playful, and that is why it is an instrument for self-expression, self-knowledge, and exploration" [44]. This category integrates toys that, in addition to serving as play instruments, help develop certain skills in children with ASD, both physical and cognitive. These differ from social robots in that they are focused on children's play and fun. However, these functions can be complemented by the development of certain skills. In addition to this, they usually integrate a lower technology, which causes them to usually have specific functions and do not present multifunctionality. This AT is generally better value for money and, therefore, affordable and available for family settings. It should be noted that 100% of articles that develop toys specialized in ASD conceptually identify the importance of collaborative play, but no research obtains representative results related to functional and non-functional requirements to be included in the products, as well as preferences in terms of usability (efficiency, effectiveness, and satisfaction in the interaction between children and ASDproduct).
It should be noted that "play" is an "intrinsic activity, playing for the sake of playing, which arises as something spontaneous and voluntary, not out of obligation, and includes an element of pleasure, because it is done to have fun" [9]. Collaborative play can intervene not only in the playful field, but also in the sensory, motor, and cognitive. It is important to create communicative environments in games and play, to give the child the possibility to express desires and needs and develop their communicative skills. It is essential to create situations that require him to ask for objects, comment, protest, etc. These strategies introduce the user to a cause-and-effect process, improving attention, tracking visual stimuli, and recording instructions. In cooperative play for children with ASD, the verbal description of each activity during the process is very important. For this purpose, the need to introduce adapted reinforcements (visual, auditory, tactile . . . ) is created [3]. It may also be beneficial to allow the child to choose his own materials and adapt the game according to his preferences. In addition to this, it is important that the game has a clear context [4] and resembles real-life interactions [3]. Similarly, during cooperative play, it is possible to observe parameters such as the level of correspondence, the degree of alternation between playmates, and the degree of variability in responses, which are properties of reciprocal interaction that can indicate the level of social development [3]. The lack of research that develops new knowledge related to collaborative play through interactive and smart products and AT to improve the social and collaborative skills of children with ASD makes it a line of work of interest, given the importance of these skills in the quality of life and independence of these users.
From the last category "COVID and Autism" we could deduce that COVID-19 has imposed changes on everyone's social life and the job market that could be sustained and made permanent, causing physical and mental challenges to the population. As a result of this new reality, improved family and work conciliation will be necessary, which will be particularly difficult for families with children with autism [45][46][47][48]. Thus, it is further underlined that there is a need for solutions to assist parents in balancing employment and the care of these children. One of the main disadvantages of these products is their affordability; due to their high price, they are mostly used as professional tools in therapy, but cannot be used in a domestic context. Therefore, from this category, it can be deduced that there is a need for products that are affordable, aimed at a domestic context and that can be used at home by parents and children.

Patent Applications of Assistive Technology
This section shows the results of the analysis of assistive technology patent applications to improve the social and collaborative skills of children with ASD.
The IPC Code Map (Figure 6a) represents the areas of scope of the 55 patents of the selected sample, the most common being: (1) A-HUMAN NECESSITIES, more specifically in A6-HEALTH; AMUSEMENT ( Figure 6b) and (2)      sentative being: (1) A61B 5/00 Measuring for diagnostic purposes (29.09%); (2) G16H 20/00 ICT specially adapted for therapies or health-improving plans (14.55%), (3) G09B 19/00 Teaching not covered by other main groups of this (14.55%). Code (4) G10L 25/00 Speech or voice analysis techniques not restricted to only one of the groups (10.91%), (5) A61M 21/00 Other devices or methods to cause a change in the state of consciousness (10.91%), and (6) B25J 11/00 Manipulators not otherwise provided for (10.91%). By grouping similar IPCs, it is possible to create clusters of patents organized into sections and technological areas. In the case of the sample analyzed, the following sections were obtained: (1) Electrical Engineering, (2) Instruments, (3) Mechanical Engineering, and (4) Other Fields, whose technological areas are shown in Table 9. By grouping similar IPCs, it is possible to create clusters of patents organized into sections and technological areas. In the case of the sample analyzed, the following sections were obtained: (1) Electrical Engineering, (2) Instruments, (3) Mechanical Engineering, and (4) Other Fields, whose technological areas are shown in Table 9. From patent analysis, it is possible to obtain particularly interesting information about the innovation potential of the sector. For this purpose, the "evolutionary potential analysis" was used; this evaluation shows a list of properties as well as their relevance within a selected patent sample. Likewise, it establishes a quantification indicator, called Nominal value (Figure 8a), and a weighting indicator, called Relative value (Figure 8b).
First, the nominal value indicates the number of patents in the sample that deal with a particular property; it analyzes the total number of patents that prioritize a property within the sample. In the selected sample, the priority properties are Information and Automation along with other less frequent properties such as Taste, Porosity, or Components. On the other hand, the relative analysis shows the use of each property in the total number of patents in the sample; this indicator identifies the innovation potential of each property, which is represented in the white space of the graph. In the selected sample, the Taste, Smell, or Market properties have great innovation potential.
The search, selection, and analysis of patents were divided into three types of products: "Virtual environments" (Table 10), "Robots" (Table 11), and "Toys" (Table 12).  Within the "Virtual Environments" group, different types of environments are identified. Several patents develop therapy devices, such as those of [49] that focus on the recognition and expression of emotions through videos; and [50] a wearable that, by analyzing the child's eye contact, verbal interaction with the caregiver, and repetitive movements of the head and body, performs an analysis and monitoring of the evolution of the child. Likewise, patents focused on the analysis of children's social skills are common with the aim of identifying and detecting signs and symptoms of autism; making use of sound analysis of the environment with microphones and recorders [51,52] or using motion detection cameras [53]. Highlight the proposal of [54] with a comprehensive rehabilitation training system based on 3D printing technology, with different modules to train different skills.
Regarding virtual platforms, the proposals aim to develop language and communication based on image exchange systems (PECS) [55], develop concrete skills through reward systems [56][57][58], or improve skills through gamification (games) [59]. Some virtual environments allow the user to create simulation units that are used to present images of avatars or characters, social scenes, and situations and stories that improve collaboration [60].
Specifically, of the virtual environments intended for collaboration, those that use virtual reality systems to present social situations stand out [61][62][63][64][65]. In addition to this, there are some proposals that can be linked to other types of product, such as robots [66].  Regarding robot development, designs include multiple sensors that allow for detecting different aspects of human-machine interaction (HMI); such as vision cameras and voice modules, useful for automatically recognizing the patient's emotion and deducing the meaning of language according to their facial expression [69], or for recognizing emotions and creating a conversation and interaction according to collected data [70]; displacement sensors, sound pickup, facial expression recognition, behavior recording, voice output for visualization of emotions [71]; or user-programmable processors [72], in order to instruct the robot to perform therapeutic interactive movements, gestures, and audiovisual signals. They also combine image acquisition devices with sound collectors and players [73], or motion sensors to capture motor reactions of users [74,75]. These robots that monitor information also allow in many cases to adapt and personalize the interaction in a way that improves and makes more comfortable the child's interaction with the ASD-Robot. In addition to this, they also serve to monitor and follow therapy progress [76][77][78].
With respect to the functional scope of robots, in general, the most developed categories are the recognition of emotions and facial expressions [79]. It is worth highlighting the proposal of [80], an emotionally expressive robot that participates in sensory experiences by reacting to stimuli that simulate typical everyday experiences, such as uncontrolled sounds, light, or tactile contact with different textures. The goal is to teach children with ASD to express their emotions toward different sensory experiences; or the robot developed by [81], which uses the automation of behavioral analysis to provide treatment and evaluation of emotional communication and social skills for children with autism. Proposals for the development of language and communication are also common, [82], as well as for improving imitation skills, which are of great importance in social skills [83] or in improving eye contact [84]. Robot patents that are intended for the domestic context allow to work on different skills of daily life [85] or identifying objects (using for example, RFID tags next to a verbal or gestural response) [86]. In addition to this, robots can be combined with other types of products, such as virtual environments, such as holograms [87].  Lastly, assistive technology patents in the form of toys combine traditional elements and components (natural materials, textures, bubble generators, snap-in blocks, levers, joints, wheels) with computational and technological elements (LCD screens, microphones, speakers, projections, motion sensors, light and sound sensors, cameras, touch sensors, buttons). The proposals are presented in the form of objects and characters from everyday life: such as trains [89], musical instruments [90], geometric shapes, and building blocks [91,92], babies and children [93,94], balls and other sports equipment [95], puzzles [96] or animals [97].
To meet these needs, products usually integrate different support stimuli such as musical sounds, textures, static and dynamic images, lights, fine and gross motor movements, imitation, interaction with a playmate, or interaction with the product in the form of conversation.

Analysis of Companies and Commercial Solutions
Analysis of the supply-demand relationship of TA products for ASD showed that there are few companies dedicated to the design, manufacture, and marketing of these kinds of products, with the "low tech" and "mid-tech" being the most frequent scopes and "high tech" products being less common in the portfolios of the different organizations. Most of the companies belong to the toy sector. It should be noted that of the selected companies, 61% of the organizations found are developers and manufacturers, the rest being distributors and marketers. As for the headquarters, most of the manufacturers are located in the USA. However, they are harder to find in European or Asian companies. For this analysis, a sample was selected with a total of 18 companies with the following distribution: 5 manufacturing companies, 6 manufacturers and distributors, and 7 distributors. The selection was carried out according to the following criteria: the variety of products offered, the scope of distribution, and the adaptability of the products to the specific skills of the ASD.
A selection of companies dedicated to the mid/high tech assistive technology sector for children with ASD was made. Of the 6 selected companies, 2 are dedicated to the creation of virtual content, 2 to the development of assistive robots, and another 2 to the development of interactive and intelligent products of medium-high assistive technology.
Additionally, of the 6 companies selected, 5 are developers, manufacturers, and producers of such products.
Many companies dedicated to assistive technology for children with ASD belong to the toys sector, since toys are essential tools for the motor, cognitive, and social development of these children. Thus, there are several companies dedicated to the development, manufacture, and distribution of these toys. A selection of 12 toy companies was made; however, only 6 of them are manufacturers of these products, and the rest of the companies are only dedicated to sale and distribution. Therefore, it was concluded that there are very few companies dedicated to the development and manufacture of toys for children with ASD.
Similarly, manufacturing companies were classified into two groups according to their scope: (1) the toy sector and (2) the medium-high technology TA sector. First, this analysis focused on the toy sector. In general, the product portfolios of the toy sector have a wider variety; they are structured according to (1) target audience (type of disability, age), (2) type of product (educational, playful, furniture, etc.), and (3) needs and skills to be developed. In this last group, 62 different categories of toys were found. Table 13 shows the 7 most common categories among toy companies. As can be seen, "language and communication" and "social" skills, both related to collaboration, are among the most common within companies' product portfolios. The number of products offered by the companies presented in this study is 112,234. After an analysis of these products, a classification was made in the 7 most common categories presented in Table 11. This classification of products is shown in Table 14. In this table, it can be observed that "social" and "language and communication" skills, both related to collaboration, are again among the two categories with the highest offer of products. Analyzing products dedicated to the use of strategies and collaborative actions for the development of skills, the offer of products amounts to 1784. These were classified into the subgroups of Figure 9, where the parameters "number of items" and "participation by category" are shown in %. As can be seen, the categories of social skills', "Language and communication", "Board games" or "emotions" have a wide variety of products compared to the categories of "cooperation", "Toys for family and friends", "cause and effect", and "education in values" with a very scarce offer. The results show a deficiency of products dedicated to the development of collaboration and cooperation, especially games and toys that allow the participation of several users simultaneously. This situation is a niche and a market opportunity, given the importance of collaborative and cooperative play in the development of skills, which has been widely demonstrated [3,4,6,9,10]. At this point, the AT products are analyzed. Below is a selection of 27 assistive technology products dedicated to improving the social and collaborative skills of children with ASD. These products were divided into three groups: Virtual Environments (Table  15), Robots (Table 16), and Toys (Table 17); these products are a representative sample of the global offer available in the market. ECO is an augmentative and alternative communication system (AACS) that, through images, videos, audio, and texts, provides help to people with difficulties in communicating. It has been designed and validated in close collaboration with real entities and users.
Free Figure 9. Categories of toys related to collaboration.
At this point, the AT products are analyzed. Below is a selection of 27 assistive technology products dedicated to improving the social and collaborative skills of children with ASD. These products were divided into three groups: Virtual Environments (Table 15), Robots (Table 16), and Toys (Table 17); these products are a representative sample of the global offer available in the market. ECO is an augmentative and alternative communication system (AACS) that, through images, videos, audio, and texts, provides help to people with difficulties in communicating. It has been designed and validated in close collaboration with real entities and users.

Free 9
Injini [112] It is stimulating and feels like a fun game, promoting the development of fine motor and language skills, as well as spatial awareness, memory and visual processing, and understanding of cause and effect.

€
10 Proloquo2Go [113] Communication app for people who cannot speak or need help being understood. Features natural sounding voices, including real children's voices; AAC (augmentative and alternative communication) tool. Toy version of Keepon Pro, developed in partnership with UK-based Wow! Stuff. In its touch mode, it responds to pokes, pats, and tickles with a wide variety of emotional movements and sounds. In its dance mode, it hears the beat of music or clapping and dances in synchronized rhythm.
40 € Table 17. Sample of commercial products in the form of toys.

18
Resonance microphones [121] The voice is amplified through the soundboard. It promotes sensory development by stimulating speech, language, and curiosity.

19
Visual sequences of tasks [122] It shows the sequences of an action to be put in order. Working on the decomposition of events into actions, we manipulate more abstract concepts such as the past, present, and future.

20
Repeating toys [123,124] A toy that repeats everything the child says. It encourages children to work on the articulation of words, the time, and the volume to which we speak.

21
Tell me what you see [125] It includes a book with pictures and a set of figures. These products were analyzed based on the categories of social skills identified in Figure 10. The results are shown in Figure 10; the different colored circles differentiate the types of products: orange "applications and virtual environments", green "robots", and blue "toys". The numbers correspond to the ones on Tables 15-17.

26
Table of light [130] It is a large table that allows you to paint on it. It has lights that make the paintings look neon. Allows children to collaborate on the same These products were analyzed based on the categories of social skills identified in Figure 10. The results are shown in Figure 10; the different colored circles differentiate the types of products: orange "applications and virtual environments", green "robots", and blue "toys". The numbers correspond to the ones on Tables 15-17. These results are consistent with those shown in Tables 13 and 14. The categories "Social Skills" and "Language and Communication" are the most offered, followed by "emotions". The rest have a very reduced offer. The results show a low availability of These results are consistent with those shown in Tables 13 and 14. The categories "Social Skills" and "Language and Communication" are the most offered, followed by "emotions". The rest have a very reduced offer. The results show a low availability of assistive technology products in relevant categories such as "Cooperation", "Board Games", or "Education in Values", which require multi-user interfaces for their use.
From the analysis of Tables 14-16, it can be concluded that technology related to automation, self-adaptation to the environment, intelligent behavior, autonomy in interaction, and multifunctionality significantly increases the cost of products. It should be noted that the price of the most advanced robots amounts to 21,000 euros; they are usually intended for professional therapy settings and are not affordable for domestic contexts. The toys available for families do not incorporate the technological level; nor do they follow the trends of products intended for typically developing children. The situation described generates a negative impact on this group. The lack of availability and access to this type of product reduces the possibility of working more efficiently on some needs related to social skills and communication; instead, families should use products with similar functionality but designed with virtual interfaces; generally, these are available through mobile applications, for which there is a greater offer at more affordable prices. However, these lack tangibility and materiality, aspects especially important for the usability specialized in ASD [37]. The inclusion of tangible elements makes an interface more intuitive, in addition to providing tactile stimulation to the user, a key requirement to increase children's interest in a product.
Lastly, the results show a lack of medium-high-technology assistance products dedicated to the development of social and collaborative skills, especially in the categories "Cooperation", "Board Games" and "Education in values"; likewise, the analysis reveals an insufficiency in the availability of products with an adequate quality-price ratio to familiar environments. This situation is a niche and market opportunity for developers and manufacturers.

Technological Trends in Assistive Technology for Children with ASD
Within the field of products for autism spectrum disorder, one of the main research areas is focused on the development of assistive technology. The International Classification of Functioning, Disability, and Health (CIF, WHO, Geneva, Switzerland) defines assistive products and technology as "any product, instrument, equipment, or technology adapted or specially designed to improve the functioning of a person with a disability" [132]. Assistive technology tools have a significant impact on the well-being of children with autism spectrum disorder, providing new opportunities for therapy methods that are meant to improve different skills that contribute to the integration of these children into society. This assistive technology differentiates between: • Low-tech: traditional tools and methods that use non-interactive products or do not use energy). • Mid-tech: include simple electronic elements, such as recorders, e-books, headphones, and visual timers. • High-tech: include electronic and computerized elements that improve efficiency, speed, and accessibility.
Low-tech tools used in language therapies are based on alternative and augmentative communication systems (AAC). They use symbols or images to facilitate communication and expression. The Picture Exchange Communication System (PECS) is one of the most common approaches, helping users communicate their needs and preferences through images [133]. Users usually carry these images and symbols in a book. Despite the benefits related to manufacturing cost, ease of use, or environmental impact, low-tech tools are not flexible and do not adapt to the evolution of user needs. For this purpose, mid-tech [134]) and high-tech products integrate interactive and smart functions with multisensory reinforcements, making the user experience more intuitive, adaptable, and dynamic. Furthermore, the health sector is significantly influenced by the concept of "Industry 4.0", taking advantage of enabling technologies such as process automation, digitalization, and emerging information and communication technologies (ICTs) that have been powered by the Internet of Things (IoT), obtaining cyberphysical systems and smart products [135].
In addition to having an immediate positive influence on communication abilities, assistive technology can help children with ASD enhance their social skills [24]. These instruments are predictable, and the repetitive nature gives the child a better sense of security [136]. Since they can offer continuous feedback, they are also simpler to comprehend. To address the current social challenges, the concept of "sensing, smart, and sustainable (S3)" originated in this setting [137]. The ability of a product to recognize changes in the environment is referred to as the "sensing concept". The term "smart concept" describes a product's ability to combine control and actuation functions in order to understand situations and take decisions in a predictive or adaptive way. Finally, the "sustainable concept" is employed to create sustainable products while taking economic, social, and environmental design objectives into consideration.
The interactive properties of these products allow for different modes of interaction. Some of the most common ones in the literature are:

•
Dialogue interaction: users interpret interaction as a conversation in which the various components are employed to convey information and await a response. [138]. • System interaction: the method by which the product gathers data and interprets it in order to later mold and determine how the conversation will proceed [139]. • Tool Interaction: users are in control of the product and use it for a certain purpose. The initiative is on the user's side [139]. • Media interaction: the product mediates communication between people [139]. • Transmission interaction: the product presents information to the user for him/her to learn and interpret [138]). • Implicit interaction: the product reacts to human or non-human activity state [138]. • Agent-based interaction: how the user-product interaction develops is determined by the user's instructions to carry out a particular task [37].
These interactive qualities are linked together. When they are combined, the interaction can be adjusted to the child's development, leading to an evolution of dialogue.
These products may also be classified as smart products depending on their features. Smart toys "are new forms of toys that incorporate tangible objects and electronic chips to provide two-way interactions that lead to purposeful tasks with behavioral or cognitive merit" [140]. The seven characteristics of a smart product, according to Rijsdijk and Hultink, are personality, human contact, capacity of cooperation, multifunctionality, reactivity, adaptability, and autonomy [141]. In this way, these characteristics are used to evaluate how smart a product is.
Therefore, in order to design the interactive and smart qualities of products, two domains must be taken into account [135]:

•
Sensing domain: sensors selection, electronic and electrical design, and mechanical design, in order to design a sensing system. • Smart domain: design of the smart functions and components, as well as connectivity system, and integration with the physical components.
For the above reasons, some of the most important topics, research lines, and opportunity areas regarding technology and the treatment and well-being of people with autism spectrum disorder include: Robotics, Digital imaging processing, wearable systems, Internet of Things, Telemedicine, Digital medicine, and mobile apps, Communication networks, Monitoring systems, Cognitive computing, Machine learning, Big Data, Analytics technics, Human-machine and AI interfaces, and Augmented and Virtual Reality [142].

Discussion
The results of the state-of-the-art analysis show the reduced availability of products that act as facilitators of the special needs of children with ASD. Similarly, the unbalanced relationship between supply and demand for these devices on the market means that parents, guardians, and other personnel involved in therapy and education must choose to use unadapted products or self-manufacture them.
Among the 248 resources found focused on autism, 122 were identified as dedicated to collaboration and social skills, most of them being case studies (34.5%) focused on the development and validation of techniques and tools for the work of these skills. Similarly, there is a consolidated line of interdisciplinary research on collaborative design and codesign between the different agents involved in the vital context of children with ASD (teachers, parents, therapists, educators, psychologists, and health professionals). However, there is a clear shortage of design methods and tools dedicated to the development of assistive technology that improves the collaboration and social skills of children with ASD, being more frequent in the low-tech category, and less for mid/high-tech.
It should be noted that the scientific community is concentrating great efforts on demonstrating the benefits of mid/high-tech assistive technology. Most resources are allocated to the development of applications or virtual environments, especially those focused on improving collaboration and social skills. These types of proposal can be very beneficial, as they offer great flexibility in content and personalization. Different studies have shown the potential of these applications in the therapy of children with ASD [2,4,6,[14][15][16][17][33][34][35][36]. However, most of these resources remove tangibility and materiality features from the design, especially important aspects that make the interface more intuitive, offer better tactile stimulation for users with ASD, and increase the interest of children in the product [37]. Similarly, there are a greater number of patents dedicated to virtual environments and applications compared to interactive toys or robots focused on social and collaborative skills. Most of these patents focus on the recognition of emotions or communication and language; however, a lack of proposals of products that improve cooperation skills (collaboration of several users simultaneously) was identified.
In the commercial context, there is a large number of companies dedicated to products for children with ASD. Of the sample analyzed in this work, 61% correspond to manufacturers and developers, and 49% are dedicated to sales and distribution. However, specifically for the toy companies, only 50% are manufacturers, the rest being distributors. That is, there are few companies dedicated to the development of toys for children with ASD, and the solutions proposed are mainly from research centers. Within the product portfolios of these companies, the most offered product categories are related to the development of "social skills" and "language and communication" (both related to collaboration). However, the available products lack multi-user interfaces, which prevents these skills from working optimally, as it does not allow the participation of several users simultaneously. This situation is a niche and market opportunity, given the importance of collaborative and cooperative play in the development of other skills. It should be noted that the value for money of high technology, specifically in the case of therapy robots, makes the cost of this type of product very high. This situation causes these devices to be destined for therapy and professional settings, as they are not affordable for most families. In contrast, products in the low-and mid-tech categories do not integrate technology and trends similar to those currently available in toys marketed for typically developing children; this situation causes inequality for this group. To solve the above inconveniences, families choose to use mobile applications, with a higher offer and lower prices. The results show the existence of current unmet demand for medium-high assistive technology products, specialized in social and collaborative skills, specifically in the categories of "Cooperation", "Board Games", and "Education in Values".
As a final contribution and based on the results of the review, a proposal of the most relevant lines of work that can contribute to knowledge related to the design of interactive and intelligent products for children with ASD is offered: • Improvement and proposal of new methods and design tools for assistive technology products that are correctly adapted to the user with ASD and aimed at improving collaboration and social skills. • Identification of the needs and technological preferences of children with autism, as well as the adaptations (physical, cognitive, and sensory) of mid-and high-tech AT products according to the signs and symptoms of the condition. Integrate in an equitable way the technological development trends available in the market for users with typical development, to end the technological gap of the ASD collective. • Study of the optimal "aesthetic-functional" requirements for AT for autism. Current digitalization trends must properly integrate the balance between tangibility and virtuality, combining traditional strategies, methods, and materials with new technologies. This balance will allow the user to have more comfortable, flexible, and adaptable products for the user with ASD.

•
The development of assistive technology meant to improve collaboration and social skills through multi-user interfaces, which guide the game to cooperation and education in values. These can be beneficial for the integration of this group into the society from an early age.

Conclusions
This work carried out an exhaustive analysis of the scientific literature, as well as market research and trends, in order to explore the state-of-the-art of assistive technology and interactive and smart products for children with ASD, specifically those aimed at improving social and communication skills. This work identifies the need for therapies to include correctly adapted products that facilitate positive interdependence between the child with ASD and his playmate. The results show an unbalanced relationship between the supply and demand for these devices in the market. They also identified a clear lack of design methods and tools dedicated to the development of AT products that improve the collaboration and social skills of children with ASD. The scientific community is concentrating great efforts on demonstrating the benefits of mid/high-tech assistive technology. However, most of the resources are allocated to the development of applications or virtual environments, which eliminates from the design of the devices the characteristics of tangibility and materiality; these aspects are especially important for the intuitiveness and stimulation of users with ASD. It also follows in both the commercial sector and the field of patents that most products and inventions focus on the recognition of emotions or communication and language, but there is a lack of products dedicated to the development of cooperation and education in values for children with ASD. It should be noted that given the importance of collaborative play for the development of personal and social skills, it would be interesting to focus research on the field of interactive and smart toys, as these types of products play an important role in the development of the collaboration skills of these children. Especially, products that allow the participation of several users simultaneously through multi-user interfaces are required. Focusing efforts and research resources on these types of devices will facilitate the integration of these people into society, avoiding social rejection, and favoring a better quality of life through inclusive design.
Author Contributions: Formal analysis, R.C.; investigation, R.C. and E.P.; methodology, R.C. and E.P.; supervision, E.P.; writing-original draft, R.C. and E.P.; writing-review and editing, R.C. and E.P. All authors have read and agreed to the published version of the manuscript.
Funding: This research received no external funding.