Fundamental Study On Flexible Pressure Sensors With Novel Micron Or Nano Structures

Because of the flexible properties of the flexible pressure sensors which can be attached to any surface and morphology, they are widely used in the areas of automatic control, robotics, flexible electronics, human-computer interaction, smart skin and so on. Main methos for flexibility in electronic device includes:(1)Adoption of organic materials or nano-materials in device;(2) Making hard semiconductor materials into wave-like membrane structures as well as island-bridge structures. As to pressure sensor, they can also be divided into this two types. In this dissertation, the key issues, such as theoretical modeling, fabrication process and device structure, of the flexible pressure sensors have been studied.For flexible pressure sensors based on organic and nanomaterials, different simulation models and a universal analysis process have been proposed for different mechanism and device microstructures in this area. Analysis results can cover a large part of the current research results in this field. Based on the results of simulation and the current situation that devices in this field generally does not have a linear response, high sensitivity only exist in a very small pressure range, a new research plan with Gaussian distributed micro-structures and piezo-resistive & Contact composite sensing mechanism.Based on the silicone rubber/carbon black Nanocomposite, novel pressure sensor devices with previously mentioned Gaussian distributed micro-structures have been fabricated and packaged.Tests show that linear response ranged from 0 to 14 k Pa and high sensitivity of 13.8 k Pa-1 can be achieved with this device. In another 400 times’ recycling test, the device performance remain stable. Based on this excellent features, application research with this device in flexible wrist heart rate measurement system and underwater hydrodynamics sensing have been conducted with good performance and practical results.Based on the high temperature resistance of inorganic semiconductor materials, a novel heat-resistant flexible pressure sensor has been proposed. Different from other inorganic pressure sensors with island-bridge structure and soft organic polymer substrate, all materials in this strucrue is inoganic. 200 nm thick silicon oxide wave-like membrane is adopted in this device for pressure sensing, this type structure can also certain degree of strain from substrate. Flexibility is achieved by polishing the wafer’s backside into the thickness of 80 μm. By gray-scale lithography, sacrificial layers with accurate adjustable morphorlogy can be realized. With this grey-scale lithography induced wave-like structures, high density device array can be fabricated. Other test reveals that the device has minimum 15 mm bending radius and 350 degree cntigrade thermal stability. This study has enlarged inorganic silicon-based flexible pressure sensor applications domain, its outstanding performance in high temperature resistance can not be replaced by traditional organic flexible pressure sensor.