Touch, press and stroke: a soft capacitive sensor skin

Soft sensors that can discriminate shear and normal force could help provide machines the fine control desirable for safe and effective physical interactions with people. A capacitive sensor is made for this purpose, composed of patterned elastomer and containing both fixed and sliding pillars that allow the sensor to deform and buckle, much like skin itself. The sensor differentiates between simultaneously applied pressure and shear. In addition, finger proximity is detectable up to 15 mm, with a pressure and shear sensitivity of 1 kPa and a displacement resolution of 50 m. The operation is demonstrated on a simple gripper holding a cup. The combination of features and the straightforward fabrication method make this sensor a candidate for implementation as a sensing skin for humanoid robotics applications. Summary A 3-axis capacitive sensor with a dielectric composed of elastomer pillars creates a skinlike deformation that allows detection of approach, light touch, pressure and shear. MAIN TEXT Introduction To accommodate for complex interactions between humans and robots, it is important to design a method for touch identification that can be active on fingertips and other sensing surfaces. Ideally, the approach will be scalable to cover over most of a robot's surface area, forming an artificial or electronic skin (1, 2). Such a technology is also sought for neurally controlled prosthetic devices to enhance motor control (3, 4). The functional requirements of an artificial skin include the ability to sense and differentiate tactile stimuli such as light touch, pressure and shear (1). Having a smooth and soft skin, rather than a hard or bumpy surface, helps make the surface more lifelike, while the compliance allows for lower bandwidth control systems. There is a plethora of work on flexible touch and pressure sensors.