Strain and pressure sensing tubes based on conductive fluids and their applications on a flexible finger

Soft and flexible sensors have great potential to be integrated into robotic mechanisms, for example, the prosthetic finger. Liquid conductive metals as a promising class of materials could be used to fabricate these sensors because they can undergo large deformations while retaining good electrical conductivity. Herein, commercial silicone surgical tubes with their own tubular structure are applied to fabricate strain and pressure sensing units/tubes, instead of micro-channels made by traditional shape deposition manufacturing. Many issues such as complicated fabrication process and low success rate could be solved by using the simple approach. Sensing tubes with desired patterns or multi-tube helical structures could be arranged when detecting different physical quantities. Besides, helical structures could increase the absolute resistance change evidently and then facilitate signal measurements. As a demonstration of their potential, the as-fabricated sensing tubes were used as joint curvature and three-axis contact force sensors at the fingertip integrated into a prosthetic finger, which provided better assessment of finger perception.