Carbon Allotrope-Based Textile Biosensors: A Patent Landscape Analysis

: This report aims to provide a patent landscape analysis on carbon allotrope-based textile electrodes and biosensors to measure biosignals and detect several parameters. Espacenet, a free-of-charge patent database provided by the EPO (European Patent Office) and containing data on more than 140 million patent publications from over 100 countries, was used as the reference database. The patent search was carried out by combining keywords and classification symbols. Both classification schemes (IPC–International Patent Classification and CPC–Cooperative Patent Classification) were used. As a result of this study, a total of 227 patent documents were found between 2002 and 2023. The first patent application claiming a fabric electrode arrangement with carbon black as conductive material was filed in 2002 (and published in 2004) by Philips. 2021 was the year with the highest number of published patent applications, with 36 documents. The United States was ranked first with 126 patent documents. Carbon nanotubes and graphene are the most patented carbon allotrope materials, while body temperature, motion and heart rate measurements are the main disclosed applications. We also analyzed the Orbit database obtaining 288 patent documents (vs. 227) with only 238 still active records (148 granted and 90 pending applications): the first application by Philips on an electrode arrangement is confirmed, and the patents distribution shows a peak in the period 2016–2020 (146 records available), while today it seems to be stable or even decreasing (“only” 52 records in the half period January 2021–June 2023). This outcome suggests that this material and related technology has reached its maximum exploitation or have not demonstrated a disruptive output.


Introduction
Patent survey and related content are deemed to be of great value for identifying R&D trends and improvements: thus, a patent landscape analysis (PLA) is a very useful tool able to provide an overview about a specific technology field and its exploitation status.PLA is a retrospective study because (almost) all patent applications are published eighteen months (or at least three months) after filing.However, since novel inventions are protected for a considerable time before related products/devices enter the market, patents can be seen as an early indicator of upcoming technologies and related systems and/or services [1].
In recent years, wearable systems, and smart textiles for monitoring several biomedical parameters are the most evolving and diffusing technology.In this filed, together with conductive fibers and fabric, another very promising material is carbon, in the form of fibers, nanotubes or graphene layers.Its exploration and study are still under Citation: Barbieri development and no integrated surveys about this material and its application in biomedical sensing was found.This study aims to provide a PLA in the field of carbon allotrope-based textile sensors/electrodes useful for monitoring physiological signals, such as heart rate (HR), SpO2, body temperature and other bioelectrical or mechanical parameters.

Resources and Methods
Espacenet and Orbit databases were used to retrieve patent information.Espacenet (https://worldwide.espacenet.com) is a free-of-charge patent database provided by the European Patent Office (EPO) and contains data on more than 140 million patent documents from over 90 countries.Orbit Intelligence (https://www.orbit.com) is a platform managed by Questel and it offers access to patent information through three patent databases (FamPat, FullPat and FullText).The coverage of the above-mentioned tools is quite similar, in terms of the number of documents, available full text, and updates.The patent search was carried out through a combination of specific keywords and classification symbols.Both the International Patent Classification (IPC) [2] and the Cooperative Patent Classification (CPC) [3] were used.
These systems share the same hierarchical structure, but the CPC is characterized by more subdivisions (250,000 vs. 80,000).While the IPC is adopted by more than 120 Patent Offices around the world to classify patent applications, only 30 Offices are participating in the CPC [4].CPC is limited to a narrow circle of countries [5].Therefore, both systems have to be used for obtaining a comprehensive search [6,7].This statement can be explained using the main group A61B 5/00 (Measuring for diagnostic purposes), which is the reference classification symbol for biosensors.
48,428 patent documents do not have any CPC code (see Figure 1).Therefore, the exclusion of the IPC would lead to a limited patent search.The classification and indexing codes (and the corresponding definitions) used for carrying out the patent searches are listed in Table 1.Classification codes are used to classify inventive or additional information, while indexing codes are helpful to categorize additional information only and to specify aspects not covered by the classification scheme.Moreover, codes are assigned according to the structure, or the function/application of the subject matter claimed in a patent.
A patent search can be carried out on one or more patent databases.Usually, the collected results are different, and this depends on the specific coverage and search engine of the database.
Therefore, a patent landscape analysis should be conducted on more than one database to obtain a more complete retrieval of documents.

Results
Data were acquired by Espacenet and Orbit Intelligence platform (FamPat database).The latter is provided with a comprehensive suite for searching and analyzing patent documents [8].

Orbit Results
The patent strategy used on FamPat database is reported in Table 2.The patent search gave a total of 288 results, of which 238 are active patents (148 granted and 90 pending patent families).Four patent families were litigated and nine were subjected to an opposition procedure at the EPO.The evolution of patent filings by the 1st application year, 1st publication year and 1st priority year are shown in Figure 7.
Patents are assembled in families.A patent family is a group of patent publications on a single invention, filed by the same applicant or joint applicants in one or more countries.[10] The first application by Philips on an electrode arrangement is confirmed, and the patents distribution shows a peak in the period 2016-2020 (146 records available), while today it seems to be stable or even decreasing ("only" 52 records in the half period January 2021-June 2023).
The year 2019 has seen the maximum patent activity in priority applications filed and published patent applications.
This growing trend has been confirmed in a scientific literature search published in a recent review [11] on carbon-based textile sensors.The patent protection, publication and priority trend by country are reported in Figure 8. Patent families by protection country means the number of alive patents protected in the various national Offices.
The PCT (Patent Cooperation Treaty) procedure is the preferred solution for filing priority applications, followed by the US and China.The top ten applicants list is reported in Figure 9. Medibotics ranks first with nine patent documents (7 granted and 2 pending applications), followed by a Korean foundation and Prevayl Innovations ltd, a British company.The top ten cited patents are listed in Table 3.

Figure 3 .
Figure 3. Top ten countries per number of published patent documents.

Figure 4 .
Figure 4. Number of patent documents per type of carbon allotrope claimed.

Figure 5 .
Figure 5. Number of patent documents per type of application.

Figure 6 .
Figure 6.Top ten applicants per number of published patent documents.

Figure 7 .
Figure 7. Trend of patent priorities, filings, and publications between 2002 and 2023.

Figure 9 .
Figure 9. Top ten applicants per number of patents.

Table 1 .
List of classification symbols (IOC/CPC) used in patent searches.