Interfacial Stress Sensors For Artificial Skin Application

Biology, Information and Advanced Materials are considered to be the fastest development and the most popular research fields in the21st century. The three pillars of modern information technology are information collection, transmission and processing, corresponding to the Sensor Technology, Communications and Computer Science Technology respectively. As the source of information, Sensor Technology is the foundation and sign of modern information development, which has been widely applied to many fields. In recently years, biomechanics and medical engineering have been interested and researched world widely as a new interdisciplinary area. Artificial Skin is a new research focus in the area which applied sensor technology to biomechanics and medical engineering.As a new research focus in biomechanics and medical engineering, the in-terfacial stress distribution between amputee and prosthetic sockets and plan-tar stress distribution have attracted more attentions of doctors, scientists and athletes in research areas and industries of rehabilitation medicine, orthopedic surgery, sports training and footwear. To measure these two interfacial stress distributions, this work has been developed a novel plate capacitive stress sensor and a novel surface acoustic surface stress sensor for artificial skin application-s, and developed a new artificial skin based on these two novel stress sensors. The new artificial skin is capable of measuring3D and micro interfacial stress simultaneously. Specific research contents and innovations are as follows:1. A novel interfacial stress sensor based on plate capacitance was developed, the sensor is capable of measuring3D interfacial stress. To measure3D interfacial stress, we designed a novel plate capacitive in-terfacial stress sensor, which is based on multi sensing electrodes and hyper elastic-plastic material of PDMS. The sensor has a smaller size, larger mea-surement range and higher sensitive. It is capable of measuring a range of0to220kPa compressive pressure and a range of0to70kPa shear stress with a maximum error of5%and14%respectively.2. A novel interfacial stress sensor based on surface acoustic wave device was developed, and the sensor is capable of measuring mi-cro interfacial stress. Since the novel plate capacitive interfacial stress sensor has a maximum error of5%, it can not measure a range of stress less than11kPa. To overcome this shortcoming, we designed a novel sur-face acoustic wave interfacial stress sensor, which is based on delay line structure SAW devices. The sensor has an higher accuracy and better anti-interference. It is capable of measuring a range of0to20kPa micro stress with a maximum error of3%.3. The linear regression mathematical models of the two novel in-terfacial stress sensor are built, and the models are solved by the least squares method. When a compressive pressure is applied to the novel plate capacitive stress sensor, the input-output function is not a lin-ear function. We deduced the function type when the sensor is applied to compressive pressure and built the regression model of the sensor. S-ince the model is not a linear function, we linearized the model and solved the linearized model by the least squares method. When a shear stress is applied to the sensor, the output capacitance of the sensor is changed not only depending on compressive pressure but also on shear stress. The input-output function is multi-linear function. We linearized the model and solved it by the least squares method. When a micro interfacial stress is applied to the novel surface acoustic wave interfacial stress sensor, the input-output of the sensor is a simple linear function. We built the linear regression model and solved it by the least squares method.4. The key problems in the design of two novel interfacial stress sensors are studied and solved. The key problems in the design of plate capacitive interfacial stress sensor include design process, the determination of the measurement range, the sensor size, the selection of the intermediate layer material, the design of mechanical part and electrodes coupling. The key problems in the design of surface acoustic wave interfacial stress sensor include the selection and cutting of the substrate material, the selection of the structure of SAW device, the design of the cantilever structure, the layout design, the input-output frequency side-lobe suppression and the over temperature compensation.5. Fabrication processes and methods of the two novel interfacial stress sensor are studied. The fabrication process of the novel plate ca-pacitive interfacial stress sensor includes the surface preparation, the primer preparation, the mold preparation, the fabrication of PDMS pillars, curing, remove excess PDMS material and melting max. The fabrication process of the novel SAW interfacial stress sensor includes the preparation of the piezoelectric substrate, metal film deposition, photo resist coating, expo-sure, developing, caine film, corrosion and stripping.6. The applications of the new artificial skin for measuring inter-facial stress distribution between amputee and prosthetic socket and plantar interfacial stress distribution are studied. We devel-oped the new artificial skin based on the two novel interfacial stress sensor array. The artificial skin is capable of measuring the interfacial stress dis-tribution between amputee and prosthetic socket and plantar interfacial stress distribution in real time. The novel SAW sensor also can be used for measuring the yarn tension.