A three-dimensional force/temperature composite flexible sensor

Flexible sensors that mimic human tactile perception are widely used in areas such as smart prosthetics and human-robot interaction, and play a key role in bridging the gap between humans, robots and the environment. The development of tactile sensors with versatile tactile sensing capabilities remains a challenge. In this paper, a three-dimensional force/temperature composite flexible sensor is proposed and developed. The upper part of the sensor is a temperature-sensitive unit completely covered with a hardened layer, which not only protects the temperature-sensitive material, but also reduces pressure interference. The lower part contains a truncated pyramid bump and four arrays of pressure-sensitive units to achieve three-dimensional force detection. When a three-dimensional force is applied on the sensor, four pressure-sensitive units undergo different resistance changes by which normal and shear components of the force can be decoupled. The temperature-sensitive unit is made of graphene/carbon nanotubes/silicone rubber (GR/CNT/SR) conductive nanocomposite and the pressure-sensitive units are made of graphene/silver nanoflakes/silicone rubber (GR/AgNF/SR) conductive nanocomposite. Experimental results show that force sensitivities of the sensor in x-, y- and z- directions are 1.694 N/V, 1.436 V/N and 0.435 N/V in the ranges of − 1.2–1.2 N, − 1.2–1.2 N and 0–7 N, respectively. The temperature sensitivity is 0.067 V/°C in the range of 25–90 °C. In addition, the sensor was mounted on a manipulator for daily grasping and results demonstrate good application potential.