Fabricating of a custom 3D-printed setup for evaluating gel-based strain sensors

Health monitoring systems that incorporate stretchable sensors can provide real-time feedback on a person's physical activity, stress levels, and overall well-being. For instance, stretchable sensors based on conductive hydrogels have emerged as a promising technology for monitoring physiological signals such as heart rate, respiration, and muscle activity. For developing such systems, a strain machine is accounted as the first requirement for laboratories focusing on developing conductive hydrogels as strain sensors. In this article, we present a programmable, user-friendly, and versatile 3D-printed setup designed and fabricated for measuring the strain and strain sensitivity of soft electronic materials. The setup comprises a computer (or mobile), an impedance analyzer, and the strain machine that are required for developing stretchable strain sensors in scientific laboratories. We provide a very detailed build manual on how to manufacture and use the strain machine, using an ionic conductive hydrogel based on polyacrylic acid and polyvinyl alcohol as a model system. The results demonstrated the excellent performance of the strain machine in applying programmable strain regimes to the material of interest. By offering clear instructions and a build manual, our work enables scientific researchers to construct an affordable and user-friendly strain machine to boost their research progress.