Flexibly Reinforced Polycaprolactone Bioelectrodes for Piezoresistive Sensing via Direct Ink Writing

Poly(ε-caprolactone) (PCL) is a biodegradable polyester known for its low melting point and high flexibility, making it ideal for various medical device applications. In this study, we introduce a conductive nanocarbon black-blended PCL as a reinforced ink for fabricating flexible and degradable piezoresistive bioelectrodes. This approach enables the creation of a piezoresistive bioelectrode optimized for precise biomechanical sensing. The bioelectrode exhibits exceptional mechanoelectrical stability under high tension (> 350%), repeated drawing (> 40%, 100 cycles), long-term bending (> 7000 cycles), extrusion (> 10,000 cycles), and torsion (> 90°). When assembled into flexible piezoresistive sensors, the sensor achieves a high sensitivity (2.66 kPa^-1 in the range of 0-3 kPa), along with excellent repeatability and durability (10,000 cycles at 5 N). The sensor has promising applications in human health monitoring, including finger, wrist, and elbow activity tracking, as well as knee joint space sensing for guiding precise surgical operations.