Fig. 1: Stretchable pneumatic strain gauge.
From: Integrated stretchable pneumatic strain gauges for electronics-free soft robots
a Schematic of the soft strain gauge. The measurement setup consists of a constant pneumatic resistor Rc and a pneumatic strain gauge R in series. A constant positive supply pressure Psupply is measured and applied to the constant pneumatic resistor Rc. The measured pressure between the resistor and the strain gauge is Pgauge. The strain gauge is vented to atmospheric pressure Patm. The pressure drop over the strain gauge depends on its strain. b Electric equivalent for the pneumatic circuit in a). c Relative change in the pneumatic resistance ΔR/Rc of the strain gauge as a function of the applied engineering strain ε. The five different colored curves are from different samples, and each curve is an average of five measurements with that sample. Error bars (almost too small to be seen) denote standard deviation. d A scanning electron micrograph of the channel cross-sections. e Photographs of the soft pneumatic strain gauges when they are relaxed (I), stretched (II), twisted (II), and bent (IV). Channels are filled with blue liquid to visualize them. f Photographs show the gauge in 0%, 100% and 300% strain.
