Sensitive skin is a large area, flexible array of sensors with data processing capabilities. The microsensors are integrated to give the capability of sensing several stimuli, mimicking a real skin, including but not limited to temperature, touch, and flow. The objectives of this research are to integrate thermometers, micromachined infrared detectors, and pressure sensors onto flexible substrates such as commercially available Kapton as well as custom made inorganic polymers (poly (methylphenylphosphazene), [Me(Ph)P=N]n, PMPP) developed under the current NSF grant. In addition, a feasibility study will be done to incorporate flow sensors. The use of multi-sensory arrays is particularly attractive to robotics applications where operators would like to have a "human-like" sense of the environment. Micromachined, distributed multi-sensory arrays will be fabricated on the flexible polymer substrates. The mechanical, electrical and optical sensory performance of the micromachined sensors will be measured. To maintain low cost, it will be important to utilize standard Si fabrication equipment. This investigation will employ standard micromachining techniques with polymer-coated wafers to allow standard fabrication equipment to be employed. Upon completion of the fabrication, the polymer will be released from the wafers to provide a flexible substrate. The outcome of this research is NOT a product that would replace human skin, but a product that would emulate the functions of a human skin on inanimate objects such as robots, aircraft, and other macro- and micro-scale machines. Intellectual Merit: This is the first known effort to build micromachined, integrated, multi-sensory arrays on flexible substrates. Challenges include thermal budget restrictions of the underlying polymer substrates, mechanical integrity of the sensors on the flexible substrates, surface roughness of these substrates, signal routing, adhesion of metals to polyimide substrates, cross-talk between sensors and power supply requirements. A primary consideration in the development of flexible electronic devices is adhesion of circuit components to the flexible substrate. This is dependent upon having a substrate surface that is chemically modifiable. The science and technology developed through this investigation will enable a broad class of distributed micromachined sensors that may be produced on flexible substrates. The multisensory arrays developed in this investigation represent a step towards the development of a sensitive skin that will also include signal processing electronics. The IR microsensors will employ microbolometers that are capable of detecting broadband infrared radiation extending into the far-infrared. Piezoresistive tactile sensors with sensitivity greater than the human skin will be developed. The tactile sensors will respond to the touch-pressure exerted on the substrate as well as stress developed by bending the substrate. Broader Impacts: One of the PIs will participate in the Advanced Summer Institute for Educators that provides training opportunities for high school math and science teachers. In addition, 4th grade and 9th grade students in an Elementary and High School have been targeted for in-class presentations on flexible electronics by the research group. The activities described in this proposal, especially the applications as an artificial skin, would be attractive to youth and can be used to recruit students to science and engineering.
