Adhesive Semiconducting Polymers and Electrochemical Transistors for Conformable Biointerfacing

Integrating bioelectronics with living biological tissues to interrogate and improve health status represents an important avenue for realizing human-machine interfaces. Semiconducting polymers-based transistors (e.g., organic electrochemical transistors (OECTs)) as an advanced sensing device, are highly desired for direct electrical biointerfacing due to their low operation voltage, high sensitivity and signal-to-noise ratio. We previously demonstrated a universal and facile approach for imparting conjugated polymers with a range of functional properties including direct photopatterning and biochemical sensing. To interface with wet and dynamically moving tissues, for example, heart, brain, or sciatic nerve, conventional suturing causes tissue/device damage and cannot achieve good conformability; having the adhesive property will ease the attachment process and help achieve a conformable contact and high spatial sensing resolution. However, the use of a separate adhesive layer between the semiconducting channel and tissue can cause increased interfacial impedance. Thus, developing an intrinsically adhesive active interfacing layer will significantly improve the devices’ conformability on tissue surfaces and signal acquisition sensitivity. So far, however, to the best of our knowledge, none of the existing high-performance p/n-type semiconducting polymers are adhesive owing to a number of challenges, which pose significant challenges for using OECTs to achieve conformable electrical interfacing with wet and dynamically moving biotissues.<br/><br/>In this talk, I will present the development of an intrinsically adhesive semiconducting polymer by creating a rationally designed polymer network with interpenetrating semiconducting polymers and adhesive brush polymers to realize both high normalized maximum transconductance (~100 siemens per centimeter) and good adhesion on wet biotissues (interfacial toughness ~35 joules per square centimeter). Benefiting from the brush polymer design, the semiconducting polymer network possesses soft and viscoelastic mechanical properties (Young’s modulus ~10 kilopascal) similar to biotissues, moderate water absorption (30 %), controllable swelling (&lt;10 %), and abundant tissue-reactive groups (-COOH and -NHS), which synergically contribute to the adhesion on wet tissue surfaces. In addition, the semiconducting material shows abrasion-resistance and high stretchability above 100 % strain, which lead to the robust electrical performance. Also, the material presents good biocompatibility owing to low mechanical strain. Furthermore, enabled by the compatibility of the adhesive polymer with solution processing and vacuum deposition procedures, we fabricated an intrinsically adhesive and stretchable OECT with the adhesive semiconducting polymer as the active channel and gate and demonstrated its use for monitoring electrophysiological signals consistently and reliably on wet heart surfaces under perturbation scenarios.