Novel Single Bubble Haptic Sensor: SubbleSight

Opto-mechanical haptic sensors have emerged as a significant way to enable course and delicate touch in robotic fingers. We present a soft, affordable, vision-based haptic sensor named SubbleSight, which provides magnitude and direction force by the interactive surface. The sensor is of a single layer of Ecoflex00-31 incorporating an air bubble inside it. The air bubble is injected into the Ecoflex sample while curating to stabilize the bubble inside the elastomer. The elastomer receives light from a smartphone, and the camera in another smartphone records the shape change of the bubble during force interaction. The compression test models the mechanical properties of Ecoflex-00-31 with the bubble in the micro-tensile test rig, which shows the best fit with the Yeoh hyperelastic model. The parameter obtained from the model is used in the simulation to observe the shape change of the bubble to a compressive load of 5N in steps of 10mN. The simulation shows a linear relationship between load and changes in the projected perimeter of the bubble. The force resolution with a 12MP camera turns out to be 5mN for a bubble clearance of 0.384mm in the elastomer. As the bubble clearance increases, the force resolution decreases with an increase in the force range obtained from the simulation in COMSOL 5.6. The present concept and design can be used widely in areas involving multi-directional touch interactions.