Flexible 3D Printed Microwires and 3D Microelectrodes for Heart-on-a-Chip Engineering

A customized MicroSquisher system was employed for two critical mechanical assays. First, PEDOT:PSS micropillars were mechanically bent using a 0.15 mm cylindrical probe at 1 µm/s to obtain force–displacement curves and derive elastic modulus and stiffness values under dry and hydrated conditions. The customized mounting configuration allowed positioning of the probe precisely at micropillar tips for reproducible measurements (Methods 2.5; p. 4). Second, the MicroSquisher was used to generate force–displacement calibration curves for TPE/QD nanocomposite microwires using custom SU-8 tips (500–800 µm) designed to match tissue curvature. Bending tests at 2.5 µm/s established polynomial calibration functions required for converting wire deflection to contractile force during spontaneous and paced beating (Methods 2.7; p. 5). These calibrated mechanical datasets were foundational to quantifying active force, passive tension, and contractile kinetics in the heart-on-a-chip device.