Development of Polyimide-based Flexible Tactile Sensing Skin Jonathan Engel, Jack Chen, Chang Liu, Bruce R. Flachsbart*, John C. Selby*, Mark A. Shannon* Micro and Nanotechnology Laboratory * Micro-Miniature Systems Laboratory University of Illinois at Urbana-Champaign 208 N. Wright St., Urbana, IL 61801 USA ABSTRACT We present a novel microfabrication process for realizing a new type of flexible sensory "smart skin". In this work, we focus on demonstration of a skin containing a two dimensional array of tactile sensors using polyimide and metal strain gauges. A novel polymer microfabrication approach coupled with surface release methods is demonstrated. The process yields flexible sensory skins in a low cost, efficient manner. Experimental characterization of the devices is also presented. The demonstrated sensors use metal-film strain gauges in a multiplexed two-dimensional array of tactile pixels (taxels) embedded in a polyimide thin film membrane to detect force distribution on the flexible skin. The arrays have been used to image force distributions and could be used with slip-detection friction measurement for robotic gripping application. INTRODUCTION MEMS-based tactile sensing is an area of study that has potential application to robotics in medicine and industrial automation [1]. Robust, reliable tactile feedback of forces and torques, contact shape and location, and dynamic slip sensing are required for dexterous, dynamic gripping and manipulation by robots and humans through haptic interfaces [1]. Lack of such suitable commercial tactile sensors will limit development in robotic handling of fragile or irregular objects, for applications including minimally invasive surgery. Like the human skin, tactile sensors must not only serve as a source of information regarding physical contact with the external world, they must also serve as the frontline bearer of chemical and mechanical contact. A successful tactile sensor must be strong and durable as well as sensitive. Work to date has mainly focused on silicon based sensors that use piezoresistive [2,3] or capacitive sensing [4,5], and polymer-based approaches that use piezoelectric polymer films [6,7] for sensing. Other works have combined some of the strengths of silicon with polymer- based devices, such as embedding silicon sensing elements in polymer skins [8,9], or covering silicon-based devices in a protective polymer layer [2, 4, 5]. This work demonstrates the first tactile sensor array based solely on polymer micromachining and thin-film metal piezoresistors. The advantages of this approach include (1) increased robustness due to the polymer substrate material; (2) decreased fabrication cost and complexity; (3) low temperature processing (<350°C); (4) the sensor provides DC response; (5) improved strain transfer from membrane to strain gauges [10]. Silicon micro-machined tactile devices offer D4.5.1 Mat. Res. Soc. Symp. Proc. Vol. 736 © 2003 Materials Research Society