Design and Characterization of a Soft Multi-Axis Force Sensor Using Embedded Microfluidic Channels

Thin, highly compliant sensing skins could provide valuable information for a host of grasping and locomotion tasks with minimal impact on the host system. We describe the design, fabrication, and characterization of a novel soft multi-axis force sensor made of highly deformable materials. The sensor is capable of measuring normal and in-plane shear forces. This soft sensor is composed of an elastomer (modulus: 69 kPa) with embedded microchannels filled with a conductive liquid. Depending on the magnitude and the direction of an applied force, all or part of the microchannels will be compressed, changing their electrical resistance. The two designs presented in this paper differ in their flexibility and channel configurations. The channel dimensions are approximately 200 x 200 mu m and 300 x 700 mu m for the two prototypes, respectively. The overall size of each sensor is 50 x 60 x 7 mm. The first prototype demonstrated force sensitivities along the two principal in-plane axes of 37.0 and -28.6 mV/N. The second prototype demonstrated the capability to detecting and differentiating normal and in-plane forces. In addition, this paper presents the results of a parameter study for different design configurations.