Electrostatic Adhesive Brakes for High Spatial Resolution Refreshable 2.5D Tactile Shape Displays

Kai Zhang, Sean Follmer

We investigate the mechanism, design, modeling and fabrication of a scalable high resolution, low cost and lightweight refreshable 2.5D tactile pin array controlled by electrostatic adhesive brakes. By replacing linear actuators in motorized shape displays with a high voltage solid-state circuit that can be fabricated with printable electronics techniques, we can decrease the cost and complexity of such devices. Electrostatic adhesive brakes, made by patterning interdigital electrodes on high dielectric constant thin films, are used to hold metal pins’ positions and provide contact force to the user’s fingertip.We present designs of two high resolution brake modules which are 1.7 mm pitch with 0.8 mm width pins and 4 mm pitch with 1.58 mm width pins with a maximum measured dynamic loading force of 76.3 gf and static loading force of 28 gf on an individual pin (for the later size). A small demonstration of 42 pin array with a 4 mm pitch size within a row and 2.5 mm pitch size between the rows, using 1.58 mm width pins, was created. We also characterized the refresh time to be 37.5 ms for each brake, which enables refreshable actuated pin displays.

(A) A row of pins with a pitch size of 1.7 mm. Two thin PCBs are used as connectors between interdigital electrodes and main control PCB. The inset figure shows a closer view of the patterned electrostatic adhesive brake. (B) Shape pattern rendered by shape display prototype. 4 rows of metal pins are packed together for a 4 2 shape display demonstrator prototype. Each pin is individually controlled by an electrostatic adhesive brake.

Cross section of an individual electrostatic adhesive brake. Attractive force is generated by the capacitor structure which is formed by dielectric film sandwiched by metal pin and interdigital electrodes.

(A) Circuit diagram of an individual electrostatic adhesive brake. (B) System diagram of our electrical and mechanical control system.

Shape rendering process flow of our shape display prototype