Supplementary material from "A Soft Sensor-Integrated Cell Stretching Device for Precise and Reproducible Mechanotransduction"

Mechanical stretch is a fundamental regulator of cell fate, yet in-vitro replication remains challenging because conventional stretchers deliver non-uniform strain and ignore batch-to-batch variations in substrate stiffness—so the stress actually experienced by cells varies unpredictably. We introduce the first biaxial cell-stretching platform that couples an embedded soft resistive micro-channel sensor with high-frequency closed-loop control. Real-time deformation read-out (60 Hz) drives a 24 kHz actuator loop to compensate for PDMS moduli spanning an order of magnitude, delivering user-defined triangular or square waveforms (5–20 % amplitude; 0.5–10 s period) with < 2 % steady-state error. Closed-loop operation maintains strain-invariant membrane stress within ± 5 %, reducing well-to-well variability three-fold compared with open-loop actuation. Biological validation using immortalized human myoblasts exposed to 10 % cyclic stretch for 4 h produced a significant up-regulation of YAP/TAZ target genes (C-MYC, MYL9, DIAPH1, ANKRD1; p < 0.001), confirming mechanotransductive efficacy. The platform’s modular architecture accommodates stiffness-tunable hydrogels and live imaging, offering a reproducible tool for mechanobiology, tissue engineering, disease modelling and personalised mechanotherapy.