A flexible strain-responsive sensor fabricated from a biocompatible electronic ink via an additive-manufacturing process

This study developed a biocompatible, strain-responsive biosensor fabricated from an environmentally sustainable elastomeric copolymer (x-pentadecalactone-co-e-decalactone; PDL) reinforced with silver nanowires (AgNW) to create a conductive electronic ink suitable for direct-write additive manufacturing. Electrochemical characterization showed a low percolation threshold (conductive behavior emerging around ~0.4% w/w AgNW and stabilizing by ~1% w/w), with the optimized 2% w/w AgNW formulation achieving low sheet resistance (~320 Ω/sq) and high capacitance (~2.06 mF/cm^2). Cytocompatibility was demonstrated using primary mixed neural cell cultures, where PDL/AgNW substrates supported neuronal adhesion and were associated with reduced astrocyte activation relative to controls. The optimized ink was then used to print high-resolution (sub-100 µm) interdigitated electrode strain sensors via pneumatic extrusion. Under simulated physiological conditions, the printed sensors showed measurable, repeatable impedance changes under cyclic strain, remained functional for ~21 days in PBS at 37°C (≈0.9 million cycles), and produced strain gauge factors on the order of ~2–3, supporting potential use in chronic monitoring applications such as intracranial pressure/brain swelling.