Bioinspired flexible microfluidic shear force sensor skin

- Bioinspired resistive shear force sensor skin for light touch applications.
- Sensors are located away from contact area enabling multiple sensing mode integration.
- Skin fabricated from liquid metal filled microfluidic channels and compatible with large strains.
- Dynamic range is more than 10-bit with shear force up to 5 N.

There is a need to gather rich, real-time tactile information to enhance robotic hand performance during haptic exploration and object manipulation. Measuring shear forces is useful for grasping and manipulating objects; however, there are limited effective shear sensing strategies that are compatible with existing end effectors. Here, we report a bioinspired and flexible, resistive microfluidic shear force sensor skin. The sensor skin is wrapped around a finger-shaped end effector and fixed at the location of the nail bed. When the skin is subjected to shear force, one side of the skin experiences tension while the other side experiences compression and bulges similar to a human fingerpad. The tension and compression are measured by liquid metal strain gauges, embedded in PDMS, that are strategically placed adjacent to the nail bed, away from regions of direct finger-object contact. We present the sensor design, a finite element analysis static mechanical characterization model, as well as static response experiments. The resistive shear sensing skin exhibits greater than 10-bit dynamic range (up to 5 N) that is insensitive to the applied normal force. The resistive shear sensing skin is intrinsically flexible and immune to fatigue and other problems of solid-state sensors when subjected to repeated, large strains.