Gelsight sensor is a new kind of vision-based tactile sensor that can not only tell the force information but can also provide detailed information about the contacting surfaces. It is first put forward by Yuan in 2017. It has the structure as follows.
A Gelsight sensor is mainly composed of a piece of gel, a camera, LED lights, a camera spacer, and acrylic boards. The theory of the sensor is based on Photometric Stereo. When an object is in contact with the sensor, the gel is able to reproduce the tactile of the object's surface. From the camera, we can get images under the LED lights. We can reconstruct the object's surface from the images we get.
The camera we use is fisheye camera with the fov of 220° and the lights are from Cree LED. We made the camera spacer by 3D printing. The stl model can be downloaded in the following link.
The gel has 3 layers: the base gel, the reflective membrane, and the acrylic board. We use transparent polyurethane gel bought from Amazon as our base gel. Through trial and error, we finally found it effective to make the reflective membrane by mixing the tin powder and coating gel and spray the mixture onto the surface of the gel.
The 3 layers of the gel and the acrylic board
The gel we use for the reflective membrane is Hitohada coating gel. We mix the gel with fine silver powder or smear the powder carefully onto the surface. Then we use the airbrush to spray the gel onto the surface. The step is shown in the following picture. We have to spray the gel until the light can hardly go through the reflective layer.
The code for the project is here. Read the Readme file for detailed information.