A Highly Sensitive Capacitive Displacement Sensor for Force Measurement Integrated in An Engineered Heart Tissue Platform

We present a novel capacitive displacement sensor integrated in an engineered heart tissue (EHT) platform to measure tissue contractile properties in situ. Co-planar spiral capacitors were integrated into the elastomeric substrate underneath the two micropillars of a previously developed EHT platform. The capacitor plates are displaced by the tension and compression that occurs in the substrate when the micropillars bend under contractile tissue force. For a contraction force of ~200 μN, applied in the middle of pillar length, the expected change in base capacitance is in the aF range. Readout of such low capacitance changes was achieved using a commercial low-noise high-sensitivity device. Characterization of static and dynamic sensor behavior agreed with numerical simulations, demonstrating a responsivity of 0.35 ± 0.07 fF/μN. Preliminary tests with cardiac tissues proved biocompatibility of the platform, as EHTs successfully formed and remained functional for at least 14 days.