Ultrastretchable Origami Spiral Sensor Fabricated by Self-Folding of Paper

Origami-based devices offer promising avenues for wearable sensing due to their lightweight, foldability, and low-cost fabrication. However, achieving extreme stretchability, mechanical robustness, and stable sensing performance with accessible materials remains challenging. In this study, we present an ultrastretchable strain sensor based on a spiral origami structure fabricated by self-folding of paper. Localized asymmetric ink infiltration induces precise folding along printed creases, enabling the transformation from a flat sheet into the three-dimensional spiral capable of over 2076% stretchability. Silver nanoparticle electrodes, inkjet-printed onto the paper substrate, form sufficiently thin and flexible conductive layers that conform to the folded spiral geometry without delamination or loss of conductivity. The sensor exhibits high strain sensitivity with excellent linearity (R2 = 0.98) over a wide deformation range and maintains performance under repeated loading with minimal hysteresis. We also estimated the spiral geometry by comparing the folded structure with a geometric model based on the crease pattern and folding angle. Furthermore, we investigated the effects of thermal treatment and the presence of the silver electrode on mechanical properties. Notably, thermal treatment enhanced the stretchability of the spiral sensor, further improving its mechanical adaptability. As a demonstration, the sensor was successfully applied to human joint monitoring, confirming its responsiveness and conformability in practical wearable scenarios. The simple and scalable fabrication process underscores the feasibility of integrating thin-film printed electronics with mechanically amplified origami structures for next-generation stretchable, paper-based sensing systems.