Reduced dexterity in machines means delicate tasks such as lighting a match, sewing, interacting gently with a person and handling an egg are a challenge for robots. Here we report on several soft sensors being developed to address this challenge, with applications in robotics, industrial automation, medical devices and interfaces with the nervous system.
The first is a flexible soft sensor for detecting normal force and shear. Offset capacitive electrodes are used to detect both indentation of the soft, elastomeric sensors, as well as the lateral motion of the top surface relative to the bottom, characteristic of shear. A key is the use of a pillar structure in the dielectric, which increases sensitivity. Stretchable conducting electrodes are made of carbon containing elastomer, stretchable fabric or transparent hydrogels. Initial application to a roller for automated fibre placement and a mat for pressure injury warning are shown.
Two ionic sensors are also shown. The first ionic sensor is triboelectric, in which charging at the interface between an ionic conductor and a charged surface can produce more than a volt when the interface area is dramatically altered. This version of a triboelectric effect has the potential to be used in generation where high surface area changes and/or high frequency displacements are present. The second uses the piezoionic effect. This is akin to piezoelectrics, but involves the generation of current and voltage in response to pressure gradients. These gradients induce ionic currents. We show that these can generate millivolt level signals combined with currents that directly activate the nervous system, suggesting use in brain-machine interfaces.
Soft sensors have the potential to be incredibly cheap, cover large surface areas and be incorporated into robots, wearable devices, sports gear and much more. The talk concludes with a discussion of opportunities and challenges.
