All-Hydrogel-Based Organic Electrochemical Transistors for Implantable Physiological Signal Monitoring

Area of Science:

• Bioelectronics
• Materials Science
• Biomedical Engineering

Background:

• Organic electrochemical transistors (OECTs) offer efficient bio-interfacing but face limitations due to mechanical incompatibility with soft tissues.
• This mismatch hinders the clinical translation of OECTs for physiological monitoring and therapeutic applications.

Purpose of the Study:

• To develop a versatile, all-hydrogel-based OECT that overcomes the mechanical mismatch with biological tissues.
• To create a novel n-type semiconductor hydrogel for compliant bioelectronic devices.

Main Methods:

• Fabrication of a novel n-type depletion-mode semiconductor hydrogel via ionic liquid-mediated phase separation of poly(benzodifurandione)/polyacrylamide.
• Characterization of the hydrogel's ion-electron coupled transport, mechanical properties (softness), stability (1500 bending cycles), and biocompatibility.
• Integration of the hydrogel into OECTs for physiological signal transduction.

Main Results:

• The developed hydrogel exhibits efficient ion-electron coupled transport and tissue-like softness.
• The all-hydrogel OECT demonstrated high transconductance (43 mS) and stability over 1500 bending cycles.
• The devices showed excellent biocompatibility and enabled real-time human ECG/EOG monitoring and long-term subcutaneous rat signal recording.

Conclusions:

• A versatile all-hydrogel OECT platform has been established, resolving the mechanical mismatch issue.
• This technology enables robust multimodal physiological signal monitoring, including ECG, EOG, and nociceptive signals.
• The developed OECTs provide a promising strategy for implantable precision bioelectronic therapies, pain assessment, and cardiovascular health evaluation.