Guemes, A. | Search bioRxiv

bioRxiv2025

PEDOT:PSS conducting eutectogel for enhanced electrical recording and stimulation in implantable neural interfaces

Conductive polymers such as PEDOT:PSS are widely used in bioelectronic interfaces due to their mixed ionic-electronic conductivity and biocompatibility. However, their mechanical fragility and limited processability constrain their performance in implantable devices. Deep eutectic solvents (DES), when combined with PEDOT:PSS, form eutectogels that enable thick, soft coatings. Here, we present a PEDOT:PSS-based eutectogel incorporating choline chloride: lactic acid and GOPS, integrated into flexible thin-film electrode arrays for sciatic nerve interfacing. These implants feature an array of electrodes and a pre-formed spiral geometry to conformally wrap small-diameter nerves. Devices were fabricated using standard photolithography and reactive ion etching techniques, allowing side-by-side comparison of PEDOT:PSS/DES with conventional PEDOT:PSS electrodes. PEDOT:PSS/DES enabled single-layer films up to 800 nm thick, significantly greater than PEDOT:PSS, and yielding over two-fold improvements in impedance and charge injection capacity in vitro. Acute in vivo electrophysiology in rats confirmed enhanced neural recording and stimulation capabilities, with lower impedance, higher capacitance, and reduced motor activation thresholds. While PEDOT:PSS/DES more reliably elicited motor responses at lower stimulation currents, electromyogram signal amplitudes from the tibialis anterioris at matched stimulation levels were comparable between materials. These results suggest that while superior electrochemical properties improve neural interface performance, local electrode-tissue interactions remain critical. Overall, this work establishes DES-modified PEDOT:PSS as a promising electrode material for soft neural interfaces and highlights its potential for advancing implantable bioelectronics.

neuroscience↗

bioRxiv2023

Ultraconformable cuff implants for long-term bidirectional interfacing of peripheral nerves at sub-nerve resolutions

Implantable devices interfacing with peripheral nerves exhibit limited longevity and resolution. Poor nerve-electrode interface quality, invasive surgical placement and development of foreign body reaction combine to limit research and clinical application of these devices. Here, we develop cuff implants with an ultraconformable design that achieve high-quality and stable interfacing with nerves in chronic implantation scenarios. When implanted in sensorimotor nerves of the arm in awake rats for 21 days, the devices recorded nerve action potentials with fascicle-specific resolution and extracted from these the conduction velocity and direction of propagation. The ultraconformable cuffs exhibited high biocompatibility, producing lower levels of fibrotic scarring than clinically equivalent PDMS silicone cuffs. In addition to recording nerve activity, the devices were able to modulate nerve activity at sub-nerve resolution to produce a wide range of paw movements. The developed implantable devices represent a platform enabling new forms of fine nerve signal sensing and modulation, with applications in physiology research and closed-loop therapeutics.

neuroscience↗