## 5 Patents and Commercialized OECT-Based Biosensors  
Besides published articles on the topic of OECTs for sensing of metabolites, several patents have been deposited since the first developments of these devices. This is a good indicator of the degree of development and maturation of this technology.  
The first patent application concerning OECTs was registered in 2001 by [PERSON], [PERSON] and [PERSON] for the company Acreo Ab [144].  
The sensor device comprised the basic OECT structure, i.e., source and drain contacts, a gate electrode, an electrochemically active material contacting both in-between and an electrolyte in direct contact with both the gate and the electroactive material. Applications were limited to ion or humidity sensing and did not cover sensing of small organic molecules. A related patent was submitted the same year and finally accepted years later (2009) [145], where such a device was claimed to be used as electromagnetic tag with source and drain connected to two antennas. A related patent was issued more recently, which improved the design of the previously described OECT [146] but for both patent, claims did not concern sensing of molecules.  
More recently (2013), the Polytechnic University of Hong-Kong submitted a patent, issued in 2015 [147], where an OECT was claimed to be used to detect biological molecules in physiological environment. Practically, this patent suggested functionalizing the gate electrode with biomolecules such as DNA or proteins such as enzymes. An application of glucose sensing was claimed and described in detail, using a Pt gate electrode. Its originality relied on its cylindrical geometry around a filament that could be a textile yarn. The same authors proposed a related patent, issued in 2017, which is much more precise on the application for a non-invasive glucose sensor [148]. They proposed a structure in which a part of the gate electrode can be modified with a nanomaterial to increase the sensitivity. For example, they proposed a bulk Pt gate electrode covered with a composite of carbon nanotubes, chitosan and glucose oxidase, or where multi-walled carbon nanotubes (MWCNTs) were replaced by Pt nanoparticules. The patent did not propose an original transistor architecture; the limit of detection claimed was low (0.5 \(\upmu\)M with MWCNTs-CHIT/GOx/Pt, 5 nM with CHIT/GOx/Pt-NPs/Pt) but the stability was very poor (30% loss after eight days) and the linearity very poor as well (up to 1 mM glucose). On the contrary, approximately at the same period, the Korean Institute of Machinery and Materials deposited a patent describing an OECT made of linear contacts that can be textile yarns, covered by a conductive layer and embedded within a semiconducting material. Even if the inventors cite chemical sensing as a potential application of such a device, such an application is not among claims. [149].  
Related to textile, [PERSON] and co-inventors deposited in 2016 a filament-based OECT that can be put on clothes such as sport tee-shirts, aiming at measuring body parameters in perspiration through enzymatic reactions, such as lactic acid content of the sweat of an athelete [150]. Claims are not supported by experimental results, however.  
Figure 18: Schemes demonstrating the principle for SA detection based on the OECTs using the PABA modified gate. Reprinted from [107]. Copyright 2016, with permission from Elsevier.  
Last, a method of fabrication of OECT structures was deposited and accepted in 2016 [151], proposing to make devices of any shape and at high resolution without the need for mechanical or laser cutting, but no claim concerned sensing.  
This short review of the accepted patents clearly shows that, compared to classical electrochemical sensing devices, OECTs have been poorly patented up to date for (bio)sensing applications and that avenues are still open for the industrial development of these devices, in particular if there are opportunities to integrated sensing devices in non-conventional substrates like clothes.