uOECT · Stretchable micro-Organic Electrochemical Transistors Circuits for Neural Interfacing

Stretchable micro-Organic Electrochemical Transistors Circuits for Neural Interfacing

Electrical stimulation of peripheral nerves has significant potential for the treatment of a wide range of disorders, including chronic inflammation, diabetes, depression, drug-resistant epilepsy, respiratory failure, and obesity. For such treatments to be effective and safe, stimulation must be highly specific, as non-specific stimulation can lead to serious side effects. Such treatments will benefit from the development of chronically implantable, high-density peripheral neural interfaces (PNIs). In addition, advanced robotic prosthetics – which have the potential to substantially restore motor function – require stable, high-density, and long-term neural interfaces. Conventional PNIs are typically based on rigid materials such as metal wires or silicon, which are prone to cause nerve tissue damage due to mechanical stresses arising from normal body movements. Flexible polymer-based electrodes offer improved mechanical compliance but are still orders of magnitude stiffer than neural tissue. Mechanical mismatch between the implanted electrodes and surrounding neural tissue is a key factor triggering foreign body immune responses leading to scar tissue formation and loss of functionality of the implanted PNI. The development of intrinsically soft PNIs is therefore very important. For the applications described above – particularly for PNIs intended for robotic prosthetics – there is a clear need to scale up both the number and density of neural transducers. However, device scaling introduces several challenges. Scaling down electrode dimensions results in reduced neural signal amplitudes, while narrower and closely packed conducting lines lead to an overall degradation of signal-to-noise ratio. A central objective of this project is therefore to develop active neural transducers capable of sensing and locally amplifying neural signals at the recording site. Replacing conventional passive electrodes with active transducers is expected to significantly enhance signal strength and noise performance. Secondly, with the scaling up of electrode numbers, routing the conductors becomes more challenging, and a large fraction of the device real estate is utilized solely for routing conductors, resulting in a bottleneck for further scaling. In this context, the second objective of this project is to reduce the number of conducting lines by implementing integrated multiplexing electronics within the PNI. Importantly, the incorporation of active transducers and electronic circuits must not compromise the mechanical softness of the neural interface. Accordingly, this project aims to develop novel fabrication processes to enable scalable fabrication of soft electronic devices and their integration into intrinsically soft PNIs. The objectives of the project are addressed through the following activities: 1. Development and scaling of intrinsically soft organic electrochemical transistors (OECTs) to serve as active neural signal transducers and fundamental building blocks for soft electronic circuits 2. Development of novel fabrication processes based on laser micromachining for the scalable fabrication of soft OECTs and OECT-based neural probes 3. Design and integration of soft OECTs into soft implantable neural probes ready for validation through in vivo testing in a rat model

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