Transparent and flexible force sensor based on microextrusion 3D printing

Transparent and flexible force sensor provides potential applications in a lot of area such as human wearable sensor, robotic sensor and underwater equipment. Here the work presents a zig‐zag patterned hydrogel‐based force sensor. Slow‐gelling alginate hydrogel, self‐designed microextrusion 3D printer and polydimethylsiloxane (PDMS) were adapted for the sensor fabrication. A slow‐gelling hydrogel printing ink was prepared and printed onto the treated PDMS layer with a computer‐aided designed zig‐zag pattern. The line width and resistance of the printed hydrogel were precisely controlled by the self‐designed microextrusion 3D printer. To stabilise the water content, a sandwich structure was adopted and two PDMS cover layers were fabricated to seal the hydrogel sensor. Theoretical analysis was performed and it is shown that the change rate of resistance was linear related to the force, and this analysis was proved by experiment. Experiments also show that the sensor was flexible and transparent. The zig‐zag patterned hydrogel also and the PDMS layers provided stable water content and recording.