Soft and stretchable liquid metal transmission lines as distributed probes of multimodal deformations

Mechanical sensing is a key functionality in soft electronics intended for applications in health monitoring, human-machine interactions and soft robotics. Current methods typically use intricate networks of sensors specific to one type of deformation and one point in space, which limits their sensing capabilities. An alternative approach to distributed sensing is electrical reflectometry, but it is challenging to build the necessary transmission lines out of soft materials. Here, we report the scalable fabrication of microstructured elastomeric fibres that integrate tens of liquid metal conductors and have the length and cross-sectional integrity necessary to successfully apply time-domain reflectometry. Our soft transmission lines allow the detection of the mode, magnitude and position of multiple simultaneous pressing and stretching events. Furthermore, as a result of the dynamically responsive conductors, the pressure sensitivity is improved by a factor of 200 compared to rigid line probes. By integrating a single soft transmission line with a single interface port into a larger fabric, our technique can be used to create an electronic textile that can decipher convoluted mechanical stimulation. A microstructured liquid metal fibre can be used as a soft transmission line probe for reflectometry, allowing electronic textiles to be created that can decipher convoluted mechanical stimulation.