TRIZ-Based Conceptual Enhancement of a Multifunctional Rollator Walker Design Integrating Wheelchair, Pilates Chair, and Stepladder

Abstract

The development of a multifunctional invention requires several refinements for optimizing each function. This study presents a Theory of Inventive Problem Solving (TRIZ)-based conceptual framework for enhancing an innovative multifunctional assistive technology device that integrates the functionalities of a rollator walker, wheelchair, Pilates chair, and stepladder. The limitations of the multifunctional rollator walker were identified from the user feedback of a foundational work and were then addressed by identifying the engineering and physical contradictions and problem modeling using Su-field analysis. Through TRIZ Inventive Principles, the proposed design eliminates common trade-offs between portability, stability, and usability. The conceptual enhancement incorporates features such as deployable steps, the utilization of high strength–to–weight ratio material, foldability, a passive mechanical brake-locking system, retractable armrests, the incorporation of spring-assist hinges, and the use of large tires with vibration-dampening hubs. This study contributes a novel, user-focused, and space-saving mobility solution that aligns with the evolving demands of assistive technology, laying the groundwork for future iterations involving smart control, power assist, and modular enhancements.

1. Introduction

According to the World Health Organization, in 2010, as many as 1 billion people globally were living with disability [1]. In 2022, this number had increased to 1.3 billion [2]. With an increasing world population, the number of people experiencing disability is expected to increase as well. Assistive technologies, when appropriate to the person with a disability, have been shown to be powerful tools to increase independence and improve participation [1]. An assistive technology device can be defined as “any item, piece of equipment, or product, whether it is acquired commercially, modified, or customized, that is used to increase, maintain, or improve the functional capabilities of individuals with disabilities” [3]. For people with mobility impairments, common examples of assistive devices are crutches, prostheses, orthoses, tricycles, and wheelchairs. Among these, the wheelchair is one of the most commonly used assistive devices for enhancing personal mobility, which is a precondition for enjoying human rights and living in dignity [4]. Accordingly, the United Nations Standard Rules (1994) and the UN Convention on the Rights of Persons with Disabilities (CRPD 2006) urge countries to support the development, production, distribution, and servicing of assistive devices such as wheelchairs, and emphasize the importance of sharing knowledge about these technologies [4]. As such, there is a steady increase in the number of “wheelchair” publications in both Google Scholar and Scopus, as displayed in Figure 1. This is essential especially because only a minority of those in need of wheelchairs have access to them [5].

Among the wheelchair users, a number of them are elderly people. This is because as people age, changes in the skeletal muscles and joints [6] led to mobility impairment in some, leading to the need for wheelchair usage. According to a study conducted on 7026 participants over the age of 65, the number of older adults who use wheelchairs had increased significantly from 4.7 per 100 people in 2011 to 7.1 in 2019 [7]. This is also supported by Market Size and Trends that reported on the growth of the global multifunctional wheelchair market, which is primarily driven by the increasing prevalence of both mobility impairments and the rise in the geriatric population worldwide [8].

As the global population ages and the demand for assistive technologies grows, there is a pressing need for wheelchairs that not only support basic mobility, but also address a broader range of user needs, such as comfort, ease of use, and enhanced functionality [8]. In a reported study of evidence-based strategies for preserving mobility among elderly and aging manual wheelchair users, some of the recommendations include training, strengthening, and exercise to increase the capacity to handle daily mobility demands [9]. It has been reported that daily walking is effective in improving the fitness level of elderly people [10,11,12], making the rollator function useful for the target user. On the other hand, exercises using Pilates chairs have been concluded to improve balance, an important risk factor for falls among elderly people [13]. Thus, wheelchairs with features such as a rollator walker and a Pilates chair add significant value to its design. Additionally, nursing homes for the elderly often has limited space [14,15]. Thus, designing a wheelchair with the function of a stepladder for caregivers can reduce the need to purchase multiple separate devices in nursing homes, making assistive care more accessible and affordable. Moreover, nursing staff and caregivers often experience musculoskeletal disorders (MSD) due to their work environment [16]. Thus, according to the University of Melbourne, to prevent MSD, it is recommended for the staff to use a step stool or ladder when necessary to reach above shoulder level, or to lift objects overhead [17]. In a limited space like nursing homes, a stepladder is therefore appropriate to prevent MSD among the caregivers.

1.1. Conceptualization, Design and Development of Multifunctional Wheelchairs in Published Research

While it is expected that the published work on specifically multifunctional wheelchairs will be less extensive than general wheelchair studies, the former still displays an increasing trend, as shown in Figure 2. This exemplifies the growing interest among researchers in developing an enhanced multifunctional wheelchair that is better suited for its users.

Table 1. Summary of the work published on the conceptualization, design, and development of multifunctional wheelchairs.

No. of Function	Functions	Methodology	Final Product	References
4	Wheelchair Walker Pilates Chair Stepladder	Functional screening Concept sketching Concept screening and scoring Final Concept selection	No	Gan et al. (2022) [18]
2	Wheelchair Baby Stroller	Concept generation Concept selection Concept (Market) testing	No	Sangameshwar et al. (2015) [19]
3	Wheelchair A pair of crutches Stretcher	Design using SolidWorks 2019 Stress–strain analysis Materials selection Manufacturing process selection Manufacturing and assembly	Yes	Moula et al. (2023) [20]
2	Seating Wheelchair Lying Wheelchair	3D model design Motion analysis and simulation using ADAMS Static analysis	No	Rui and Gao (2019) [21]
2	Sit Wheelchair Stand Wheelchair	Conceptual design using SolidWorks Describing control architecture Designing safety features	Yes	Khaled (2016) [22]

displays the summary of published work in the conceptualization, design, and development of multifunctional wheelchairs. Most of the work published reports two to three functions, including the function of a wheelchair. The work published by Gan et al. (2022) [18] displayed the highest number of functions, including wheelchair, walker, Pilates chair, and stepladder, displaying a notable contribution to the field of multifunctional wheelchair design.

1.2. Design and Fabrication Studies of Multifunctional, Multipurpose, and Similar Inventions

Design and fabrication studies have been crucial in developing multifunctional products. As summarized in

Table 2. Summary of the published work in design and fabrication studies.

Invention	Features	Design and Fabrication Process	References
Multipurpose, portable and foldable ladder	Fixed Ladder Platform Orchard Step Ladder	Mathematical Formulation Stress analysis using SOLIDWORKS 2016 Prototype generation	Srivastava, et al. (2018) [23]
Multifunctional Lawnmower	Lower noise intensity level Operation time increased by 37% Ten times cheaper than competitors in the market	Structural concept generation Screening and scoring of structural concepts Key features scoring and combinations Final concept generation Material selection Design drawing and stress simulation Stress analysis Usability test	Kang et al. (2021) [24]
Multipurpose table	Table Chair Rack Stepladder	Functionality listing Concept generation Usability test plan Analysis plan Selection of dimensions, components, and material Simulations and analysis Fabrication of prototype Usability test	Cheng, et al. (2021) [25]
Multifunctional stretcher	Three concepts with features: Can be folded four times Hard platform Can transform between stretcher and wheelchair Reduce shock and vibration Can split vertically Handle can be folded Lightweight thermoplastic	Features screening Concept generation Concept scoring	Lim and Ng [26]
Foldable wheelchair stretcher	Stretcher Folded for storage Wheelchair	Concept selection from published study Concept dimension Component and material selection Simulation and analysis Fabrication Usability test	Lim and Ng (2021) [27]

, these studies have utilized various processes to create inventions such as a multipurpose ladder, a multifunctional lawnmower, a multipurpose table, a multifunctional stretcher, and a foldable wheelchair stretcher. While these processes are detailed, they often lack an issue- or problem-based approach, which could lead to creating a more effective invention.

1.3. TRIZ in Product Design

Originally conceptualized by Alʹtshuller (1999) [28], TRIZ provides structured tools and techniques to eliminate trade-offs, thereby enhancing the efficiency and effectiveness of engineering solutions. Since then, numerous studies have reported on the use of TRIZ in designing and fabricating their inventions, as shown in

Table 3. Summary of the published work in the design and fabrication that utilized TRIZ.

Invention	TRIZ Tool	References
Roof tile transportation and inspection system	Engineering contradiction System parameter identification Contradiction Matrix	Ng, et al. (2022) [29]
Finger grip enhancer	Cause-and-effect chain Engineering contradiction Physical contradiction Substance-field analysis	Tan, et al. (2021) [30]
Smart lawnmower	Cause-and-effect chain Technical contradiction Physical contradiction Substance-field analysis	Kang et al. (2022) [31]
Ergonomic milling machine control knob	Problem statement Cause-and-effect chain analysis Engineering contradiction Contradiction matrix Inventive Principles	Ng and Jee (2016) [32]
Device to cultivate water-drinking habits among children	Main problem definition Cause-and-effect chain Engineering contradiction Idea generation	Tan, et al. (2021) [33]
Wheelchair design for disabled elderly	Integration of Quality Development Theory (QFD) and TRIZ Identifying the needs of disabled elderly people who use a wheelchair, conducting demand acquisition, and sorting and classifying the needs to determine the weight of needs Establish a house of quality to obtain correlation between the needs of disabled elderly people and product characteristics Use TRIZ Inventive Principles to eliminate product feature conflicts	Xi and Meng-di (2021) [34]

. While contradiction models are widely used, another important but less common tool is Su-field analysis. This method offers a different perspective on the problem compared to contradictions, by looking at the interaction among two substances and a field. This method can be particularly useful for solving problems involving systems and their components, and it may offer a different perspective than a contradictions analysis.

This study builds on the conceptual work by Gan et al. (2022) [18] and the prototype development of a multifunctional stepladder by Selvanesan et al. (2025) [35]. Both these previous works integrated features and functions drawn from patent literature, existing commercial products, and relevant scientific research to design and develop a multifunctional stepladder with the functions of a wheelchair, walking aid, and Pilates chair. Based on these foundational studies, the current research aims to conceptually enhance the invention using TRIZ tools, namely contradiction analysis and Su-field analysis.

The invention formerly referred to as the “Multifunctional Stepladder” has been renamed the “Multifunctional Rollator Walker” to better reflect its primary function and intended application in nursing homes. Therefore, the following research questions (RQs) are proposed to address the problem statement of this study:

RQ1: How to analyze the engineering and physical design contradictions in the conceptual enhancement of a multifunctional wheelchair and systematically resolve them using TRIZ Inventive Principles.

RQ2: How to utilize the Su-field analysis for modeling the issues in the conceptual enhancement of a multifunctional wheelchair and resolve them using TRIZ Inventive Principles.

2. Materials and Methods

The study adheres to a multi-phase TRIZ framework displayed in Figure 3, comprising five stages: Identified Issues, Model of the Problem, Application of TRIZ Inventive Principles, Suggested Solutions, and Expected Outcome. Each stage is interconnected, allowing for iterative refinement.

2.1. Identified Issues (Problem Recognition)

As previously mentioned, this study was built on two previously published works [18,35]. Gan et al. (2022) [18] worked on the conceptual development of a multifunctional stepladder for elderly people and caregivers in nursing homes. Motivated by limitations of stepladders in terms of multifunctionality, usability and simplicity, the authors combined ideas, features, and functions from patent literature, existing products and scientific journals to conceptualize a versatile invention that functions as a stepladder, walker, wheelchair, and Pilates chair. The invention can replace wheelchairs and walkers to provide mobility assistance, and replace Pilates chairs to provide an exercise option, both for elderly people. It also allows caregivers to retrieve medical records or supplies from high places by utilizing the stepladder function. The concept (Figure 4a) offers the mentioned functionalities while saving space in the nursing home.

Selvanesan et al. (2025) [35] then designed and developed a prototype (Figure 4b) of the multifunctional stepladder based on the conceptual work performed by Gan et al. (2022) [18]. The prototype has the same functions, which are stepladder, walker, wheelchair, and Pilates chair. Using sustainable materials like mild steel and aluminum, the design was optimized through structural simulations, ensuring durability under loads up to 100 kg. Usability tests revealed that the invention saved five times the space compared to single-function products. A cost analysis highlighted its affordability, with cost approximately 35% lower than the combined cost of its single-function counterparts.

Participant feedback on the prototype of the multifunctional stepladder by Selvanesan et al. (2025) [35] noted strengths such as a presentable look, comfortable seat size, an environmentally friendly design, easy of use, and the ability to exercise on the go with the wheelchair cum Pilates chair function. Nevertheless, the participants also observed several issues with the developed prototype. Firstly, the stepladder was found to be low-efficiency, containing only two steps, which may not be sufficient to provide security and stability when climbing. Secondly, the invention was found to be bulky and heavy, making it difficult to store. Thirdly, the use of current wheels as the base could increase risk of injuries, as it risks unintentional movement when converted to ladder mode. The fourth issue mentioned was the lack of armrests for the wheelchair, which instilled a sense of insecurity in elderly users [35]. In addition to these issues, two more significant problems were observed. Continuing from the previous issues identified, the fifth issue is that elderly users with stiff joints might struggle to transform the invention, and lastly, the sixth issue is that small wheel size could prevent elderly users from reaching the wheels from a seated position to control movement, while also inducing discomfort when used on uneven surfaces.

Thus, altogether, there are six issues identified as follows:

i.

Low efficiency of the stepladder: The stepladder has only two steps, which may not be sufficient to provide security and stability when climbing.

ii.

Bulky and heavy: The prototype’s size and weight make it difficult to store.

iii.

Current wheels as base could increase risk of injuries: The design of the current wheels risks unintentional movement when converted to the ladder mode.

iv.

Lack of armrests: The absence of armrests can make elderly users feel insecure.

v.

Difficulty to transform: Elderly users with stiff joints may find it challenging to convert the invention between different functions.

vi.

Low maneuverability and comfort of small wheels: The small wheel size prevents elderly users from reaching them easily from a seated position to control the wheelchair movement. Additionally, small wheels cause discomfort to elderly users, especially on uneven surfaces.

2.2. Model of the Problem

2.2.1. Engineering Contradiction (EC) and Physical Contradiction (PC)

Contradiction analysis is a signature component of the TRIZ methodology that includes the formulation of ECs and PCs. ECs arise when improving one design parameter negatively affects another. PCs, on the other hand, involve conditions where a system or component must possess two mutually exclusive properties simultaneously.

2.2.2. Substance-Field (Su-Field)

Su-Field analysis, a core TRIZ technique, goes a step further, by identifying three-element interactions involving substances (physical objects) and fields (mechanical force, thermal energy, or magnetism). Three types of Su-fields are used to model the problems, i.e., are incomplete, insufficient, or harmful.

2.3. Application of TRIZ Inventive Principles

After modeling the problem, this study selected the suitable principles from the TRIZ 40 Inventive Principles, which are generalized solutions derived from the analysis of thousands of patents. The principles are used to explore ideal outcomes by envisioning the ideal final result, where the problem is solved completely without introducing new complications. The process involves considering how existing resources within the wheelchair system can be repurposed, reconfigured, or combined in novel ways to eliminate the need for external additions.

As a result, suggested solutions from EC and PC, and Su-field are produced, forming the conceptual enhancement of the multifunctional rollator walker. These suggested solutions are discussed in the Section 3.

3. Results

3.1. Resolving EC and PC

In the process of developing a multifunctional rollator walker that incorporates the function of a wheelchair, Pilates chair, and stepladder, two key clusters of design contradictions emerged. These two key clusters are explained below.

3.1.1. Cluster EC1 and PC1: Issue 1

EC1 is related to the issue of the low efficiency of the stepladder, due to its having only two steps. EC1 is formulated such that:

If	the new design includes additional steps for the caregiver,
Then	it will provide them with increased support and security while climbing
But	the increased number of steps will make the ladder too cumbersome and obstructive

PC1 is also related to the issue of the low efficiency of the stepladder. PC1 is formulated such that:

New design needs to include additional steps	To provide caregivers with increased support and security while climbing
New design must not include additional steps	Not to make the ladder too cumbersome and obstructive

This dilemma is common in assistive product design, where stability and minimalism are often at odds, as shown by Kwarciak et al. (2009) [36] and Ott et al. (2022) [37].

3.1.2. Application of TRIZ Inventive Principles for EC1 and PC1

The first inventive strategy employed is Principle 15—Dynamism, which led to the conceptualization of steps that are not fixed in position but instead designed to be deployable only when needed. In this approach, additional steps are built into the system using hinged or folding mechanisms that allow them to fold outwards during the conversion into ladder mode. These mechanisms can be actuated passively, triggered by user interaction or gravity-based motion, requiring minimal user input. When not in use, the steps fold neatly against the chassis, thus preserving the compact profile of the wheelchair in standard or transport mode.

Building upon this, Principle 7—Nested Doll was adopted to further address spatial efficiency. This principle inspired the use of foldable steps, wherein smaller steps slide into larger ones and are stored concentrically within the main frame. These nested components not only reduce external clutter but also maintain the device’s structural integrity and esthetic appeal. The telescoping action is supported by mechanical guides and lock-in-place pins that ensure each step can bear the required load when extended. This mechanism allows the number of visible or deployed steps to dynamically adjust based on caregiver preference or situational need, without permanently altering the device’s footprint. Similar dynamic components are found in assistive walkers and exoskeleton designs as shown by Goher and Fadlallah (2020) [38], proving their viability in lightweight mobility systems. Similar asymmetric strategies have been used in lateral support designs for patient transfer devices seen in Geonea et al. (2015) [39] and Owens and Davis (2023) [40].

To mitigate the potential increase in overall weight due to these additional mechanical elements, Principle 40—Composite Materials was applied. By incorporating advanced lightweight materials, such as Carbon Fiber-Reinforced Polymers (CFRP) or aerospace-grade aluminum alloys, the steps achieve a high strength–to–weight ratio. This not only supports user safety during climbing but also maintains overall portability and ease of handling.

By combining these principles, the device accommodates both sides of the contra-diction: it provides the necessary support when required but eliminates structural bulk when that support is unnecessary. This solution is not only supported by TRIZ theory but aligns with real-world usability expectations in clinical and home environments, as shown by Sauret et al. (2012) [41] and Gan et al. (2022) [41].

3.1.3. Cluster EC2 and PC2: Issue 2

EC2 is related to the issue of the invention being bulky and heavy, making it difficult to store it. EC2 formulated such that:

If	the wheelchair is made foldable
Then	it would be less bulky and easier to store
But	it would compromise the wheelchair’s durability and stability

PC2 is also related to the issue of invention being bulky and heavy. PC2 is formulated such that:

The wheelchair must be foldable	To make it less bulky and easier to store
The wheelchair must not be made foldable	To make it durable and stable

3.1.4. Application of TRIZ Inventive Principles for EC2 and PC2

To resolve this dual contradiction, the study adopted TRIZ Principle 7—Nested Doll and Principle 40—Composite Materials. The Nested Doll principle was realized through a folding frame mechanism embedded in the wheelchair’s chassis. The design utilizes rectangular tube-within-tube profiles, where smaller tubes slide into larger ones and lock into place using spring-loaded latch pins. This design allows the structure to be folded for transport and storage while offering robust stability during use, as each nested segment has tight manufacturing tolerances and mechanical interlocks to prevent wobble. The folding mechanism also features double-hinge geometry at critical points (such as the junction between the backrest and seat) to ensure controlled, predictable folding and unfolding actions.

To overcome the material challenges associated with thin-walled, foldable designs, composite materials can be introduced, specifically, a CFRP for the load-bearing segments and lightweight 7075-T6 aluminum for the frame sections requiring impact resistance. The CFRP provides an outstanding stiffness–to–weight ratio, allowing the frame to withstand high user loads without significant flex or deformation [15]. The integration of these materials enabled the system to meet the ISO 7176 structural safety standards for mobility devices while maintaining a total weight under 16 kg, a benchmark also achieved in similar prototypes by Moula et al. [2].

By combining the Nested Doll and Composite Materials principles, the device simultaneously achieves portability and durability. These inventive strategies are not isolated innovations; they have been validated across multiple assistive and robotic systems that require foldability and strength, such as inventions by Cao et al. [7], Kang et al. [21]. The folding wheelchair–stretcher hybrid developed by Lim and Ng [15] supports this direction, demonstrating how careful engineering and materials science can overcome what are otherwise mutually exclusive performance goals.

3.2. Substance-Field Modeling

3.2.1. Su-Field Model 1: Issue 3

Table 4. Components and description of Su-Field Model 1.

Component	Description
Model	Su-Field Model 1: Frame (S2)–Wheel (S1)–Manual Force Field (F1)
Problem	When converted into ladder mode, the wheelchair risks unintentional movement, which could endanger the user during climbing or transition activities
Purpose	Enable manual mobility in wheelchair mode
Interaction Type	Harmful Su-Field
Su-field Class	1.2.2
TRIZ Transformation Strategy	Conversion of harmful function into a useful one
	Applied Principles: Principle 10—Preliminary Action: Preemptively lock the wheels before the ladder mode is fully engaged Principle 19—Periodic Action: Engage the braking mechanism only during specific operational phases
	Solution: Introduce a passive mechanical brake-locking system that activates automatically when the wheelchair’s tilt angle exceeds a certain threshold (e.g., in the ladder configuration). No electronics are needed, minimizing cost and failure risk.
	Outcome: Enhances safety and stability in ladder mode without user intervention; especially beneficial for elderly users

displays the components and description of the Su-Field Model 1. This model addresses the issue that using the current wheels (highlited red in Figure 5) as base could increase the risk of injuries, as the wheel design risks unintentional movement when converted to the ladder mode. Through the interaction type of harmful function, Su-Field Class 1.2.2 states that harmful effects can be eliminated by modifying either of the substances involved (S1 or S2), or by introducing “nothing”, such as voids, hollows, air, or foam, or by adding an additional field. Through Principle 10 and Principle 19, the solution introduces a passive mechanical brake-locking system that automatically activates when the wheelchair is tilted to a certain angle. Figure 5 displays the solution model.

3.2.2. Su-Field Model 2: Issue 4

Table 5. Component and description of Su-Field Model 2.

Component	Description
Model	Su-Field Model 2: Wheelchair Frame (S1)–A component (S2)–Mechanical Field (F1)
Problem	Conventional fixed armrests obstruct folding and add bulk, contradicting portability
Purpose	Provide arm support for resting and stabilization during seated use
Interaction Type	Incomplete Su-Field
Class	1.1.1
TRIZ Transformation Strategy	Complete the model by adding a missing component or interaction
	Applied Principles: Principle 7—Nested Doll: Conceal components within one another Principle 34—Discarding and Recovering: Deploy only when needed
	Solution: Design retractable or folding armrests with sliding tracks or rotating joints. These can be stowed within the chair’s frame when not in use and deployed quickly for seated support.
	Outcome: Combines user comfort with structural flexibility, enabling both ergonomic benefits and compact storage.

displays the components and description of the Su-Field Model 2. This model addresses the issue of the lack of armrests (highlighted red in Figure 6), which can make elderly users of the wheelchair feel insecure. However, conventional fixed armrests obstruct folding and add bulk, which contradicts the wheelchair’s portability. Through the interaction type of incomplete function (no interaction or delayed engagement), Su-field Class 1.1.1 focuses on completing an incomplete model by adding a missing substance and its interaction through a field. Through TRIZ Inventive Principles, Principle 7 and Principle 34, the solution is to design retractable or folding armrests with either sliding tracks or rotating joints, which can be stowed within the chair’s frame when not in use. Figure 6 displays the solution model.

3.2.3. Su-Field Model 3: Issue 5

Table 6. Component and description of Su-Field Model 3.

Component	Description
Model	Su-Field Model 3: Folding Mechanism (S2)–Frame Sections (S1)–Manual Force (F1)
Problem	Elderly people who struggle with stiff joints or require excessive manual effort
Purpose	Enable easy and safe folding/unfolding of the structure for transformation or storage
Interaction Type	Inefficient Su-Field
Su-field Class	2.2.4
TRIZ Transformation Strategy	Enhance the effectiveness of the field (e.g., reduce the required force, improve the energy transfer)
	Applied Principles: Principle 8—Anti-Weight: Introduce counter-balancing mechanisms to offset lifting strain Principle 14—Spheroidality (Curvature): Optimize component geometry for smoother motion (e.g., curved hinges, rounded bushings)
	Solution: Incorporate spring-assist hinges, low-friction polymer bushings, and ball-bearing tracks within folding joints. These passive elements dramatically reduce friction and resistive force, enabling smoother transitions between configurations.
	Outcome: Improves usability and accessibility, allowing transformation even by users with limited upper-body strength.

displays the components and description for the Su-Field Model 3. This model addresses the issue of the difficulty in transforming from one function to another. This is because elderly users with stiff joints may require excessive manual effort to operate the model transformation. Through the interaction type of inefficient function, Su-field Class 2.2.4 emphasizes making the system more flexible or adaptable as part of a natural pattern of technical evolution. Through the TRIZ Inventive Principles, specifically Principle 8 and Principle 14, the solution incorporates several elements that dramatically reduce friction and resistive force, allowing a smoother transition between configurations. These elements are spring-assist hinges, low-friction polymer bushings, and ball-bearing tacks within folding joints, which are to be incorporated in the Figure 7, highlighted red. These solutions for reducing friction and resistive force are important [42,43] in reducing injuries among elderly users. Figure 7 displays the solution model.

3.2.4. Su-Field Model 4: Issue 6

Table 7. Component and description of Su-Field Model 4.

Component	Description
Model	Su-Field Model 4: User’s Hand (S1)–Wheel (S2)–Floor (S3)–Mechanical Fields (F1)
Problem	Standard small wheels limit control, increase vibration, and reduce comfort, particularly on uneven surfaces
Purpose	Provide high maneuverability and comfort during manual operation
Interaction Type	Inefficient Function
Class	2.2.4
TRIZ Transformation Strategy	Strengthen useful function by improving the field and substance characteristics
	Applied Principles: Principle 17—Another Dimension: Enable omnidirectional movement Principle 35—Parameter Change: Adjust wheel size, tread, and materials to suit diverse surfaces
	Solution: Upgrade with large pneumatic tires with vibration-dampening hubs. These allow smooth, multi-directional navigation and shock absorption.
	Outcome: Enhances mobility and comfort for users, reduces arm fatigue, and allows smoother travel over uneven terrain.

displays the components and description for the Su-Field Model 4. This model addresses the issue of inaccessible wheels (highlighted red in Figure 8), which may prevent elderly users from reaching them easily from a seated position with the aim of controlling the wheelchair movement. Through the interaction type of inefficient function, Su-field Class 2.2.4, the solution lies in making the system more adaptable and flexible, reflecting the evolution trend from a rigid to a dynamic system. Through the TRIZ Inventive Principles, Principle 17 and Principle 35, the solution upgrades the small wheels with large pneumatic tires equipped with vibration-dampening hubs. These allow the wheelchair to move smoothly in multiple directions and to better absorb shocks from rough terrain. This change enhances elderly user comfort by reducing arm fatigue and significantly improves navigation. Figure 8 displays the solution model.

Table 8. Summary of multifunctional wheelchair issues, their respective TRIZ tool used, and solutions.

No.	Issue	TRIZ Tool	Solution
1	Low efficiency of stepladder	Engineering Contradiction and Physical Contradiction	Steps are deployable when needed, foldable where smaller steps can slide into larger ones, and use high strength–to–weight ratio materials
2	Bulky and heavy		Foldable invention where smaller tubes could slide into larger ones and lock into place, and the use of high strength–to–weight ratio materials
3	Current wheels as base could increase risk of injuries	Su-Field	Introduce a passive mechanical brake-locking system that automatically activates when the wheelchair is tilted at a certain angle
4	Lack of armrests		Design retractable or folding armrests with sliding tracks or rotating joints
5	Difficulty to transform		Incorporate spring-assist hinges, low-friction polymer bushings and ball-bearing tracks within folding joints
6	Low maneuverability and comfort of small wheels		Upgrade to large tires with vibration dampening hubs

displays a summary of multifunctional wheelchair issues, their respective TRIZ tool used, and solutions.

4. Discussion

The finalized design (expected outcome) as shown in Figure 9 is a multifunctional, foldable wheelchair that seamlessly integrates the features of a stepladder, Pilates chair, and rollator walker, optimized through TRIZ principles using contradiction analysis and Su-Field modeling. It incorporates deployable and foldable steps (Principles 15—Dynamism and 7—Nested Doll) that unfold only when needed, ensuring stability without adding permanent bulk. A folding frame with spring-assisted hinges (Principles 8—Anti-Weight and 14—Spheroidality) allows an effortless transformation between configurations, even for users with limited strength. The structure uses composite materials like CFRP and aerospace-grade aluminum (Principle 40) to balance lightweight portability with high strength. Omnidirectional or pneumatic wheels (Principles 17—Another Dimension and 35—Parameter Change) enhance maneuverability and comfort across various terrains. Retractable armrests (Principles 34—Discarding and Recovering) and an auto-locking brake system triggered by tilt (Principles 10 and 19) further improve user safety and convenience. The solutions resulted in a compact, user-centric mobility device ready for further prototyping and testing.

5. Conclusions

This research has made significant effort in addressing the complex, multifaceted challenges involved in conceptually enhancing a multifunctional rollator walker through a TRIZ-based conceptual framework. By rigorously investigating and resolving two core research questions, the study offers a valuable contribution to the field of assistive technology innovation. The first research question (RQ1), concerning the analysis of engineering and physical design contradictions, was methodically clustered based on the key issues and resolved using the suitable TRIZ Inventive Principles. This process uncovered critical conflicts within traditional wheelchair designs, specifically the trade-offs between portability and durability, and between enhanced user support features and structural simplicity.

The second research question (RQ2) explored the application of the Su-field analysis for modeling the issues. The elements and interaction types were identified, and suitable classes from Standard Inventive Solutions (SIS) were selected, followed by leveraging specific TRIZ tools, such as segmentation, dynamic parts, nested doll structures, and composite materials. As a result, the method addressed the following issues of current wheels that could induce injuries, lack of armrests, difficulty in transforming the invention, and inaccessible wheels hindering maneuverability from a seated position.

The study succeeded in developing an innovative conceptual solution that eliminates the need for design compromises. These solutions were synthesized into a highly functional conceptual prototype that integrates multiple assistive features, namely, a wheelchair, stepladder, rollator walker, and Pilates chair, into a single cohesive and adaptable device.

5.1. Limitations of Study

Despite the promising outcomes, this study remains at the stage of a conceptual enhancement of a previously developed prototype. Partial fabrication has been performed; however, the invention is yet to undergo real-world testing or extensive empirical validation. User trials involving the target users, which are elderly people and caregivers, are essential to assess the practicality, reliability, and acceptability of the proposed design. Furthermore, while the current version emphasizes mechanical innovation, it does not yet incorporate powered systems or sensor-based intelligence, which are increasingly relevant in modern assistive devices. Most importantly, the current design is not suitable for individuals with advanced mobility impairments such as spinal cord injury, who require more complex modifications.

The manufacturing feasibility of the complex folding mechanisms and modular systems also warrants further investigation, especially in terms of production scalability, maintenance requirements, and cost-efficiency. Additionally, regional customization based on environmental or socio-economic factors, such as the terrain conditions of nursing homes in rural areas or affordability in low-income contexts, has not been fully addressed within this study.

5.2. Future Research

Looking forward, the study opens several promising avenues for future research. One immediate opportunity is the refinement and full-scale development of the prototype based on the conceptual enhancement, followed by structured usability testing under varied environmental and user conditions. Integrating advanced features such as sensor technology and smart systems [44,45], IoT-based monitoring, biometric sensors, and modular motorized assistance could further expand the functionality and appeal of the device. Moreover, coupling TRIZ with complementary design methodologies, such as Quality Function Deployment (QFD), Failure Mode and Effects Analysis (FMEA), and user co-design strategies, can strengthen the alignment between technical innovations and real-world user expectations.

In conclusion, this research not only demonstrates the application of TRIZ as a powerful tool for conceptual innovation in assistive technology design but also delivers a tangible outcome in the form of a multifunctional wheelchair prototype that addresses pressing mobility challenges. It highlights the value of contradiction-resolution thinking in transforming the limitations of conventional wheelchair design into opportunities for multi-functionality, adaptability, and enhanced user autonomy. By laying a robust foundation for further development, testing, and refinement, this study contributes a meaningful step toward the creation of next-generation mobility solutions that are safer and space-saving.