Research On Carbon Nanotube Based Soft Sensors And Multi-layered Stretchable Circuit

Soft electronics are very popular recently for their potential applications in areas of wearable epidermal electronics and implantable biomedical devices.Biological skin and organs are soft with curvilinear,time-dynamic surface.Soft electronics can be conformably attached with body to decrease the invasion.Carbon nanotube?CNT?is one of the most popular one-dimensional nanomaterials for the unique electrical and mechanical properties.It can present metal or semiconductor properties due to structural differences.Furthermore,carbon nanotube has a high breaking threshold and is not easy to be damaged when bent,indicating it is an ideal electronic material for soft devices.Pressure sensors,infrared sensors and biological potential sensors are very popular physical sensors for human health monitoring,such as body pulse,blood pressure,oxygen saturation,and physiological potential monitoring.Though carbon nanotube based soft pressure or infrared sensors have been studied,there are still lots of things to be optimized,such as the device sensitivity,stability,and cost.To solve the problems,firstly,infrared sensors,pressure sensors and biological potential sensors,which are all soft and based on carbon nanotubes,were designed,tested.However,it is difficult to extend the soft electronics to be widely used in real life with only device-level flexibility/stretchability for high-performance soft sensors.Because a single device cannot meet the complex requirements from daily life.Systems,that integrate multifunctional chips for signal processing and transmission,are necessary.Yet,due to the fabrication techniques limitation,it is impossible to only use the novel and soft materials to achieve system-level stretchability.So,the structure designs are presented.With the island-bridge structure,the traditional,hard,but high-performance silicon-based chips can be used to build stretchable circuit systems.However,all the stretchable circuits reported before are single-layer with low-density chips integration,which only can be used for simple applications.With materials improvement and advanced fabrication method,we presented the new protocol that can be used to build multilayered stretchable circuit with high-density chips integration.And at last,the high-performance bio-potential sensors are integrated with stretchable circuit system for health monitor and human-machine interface.Main results are summarized as follows:?1?Design and fabrication of multi-walled carbon nanotube based infrared sensors.Cost of signal-walled carbon nanotubes is high,but response speed of multi-walled carbon nanotubes based infrared sensors is slow.We found the interface effects between carbon nanotubes and SiO₂ can highly improve the response speed.By transfering the interface,flexible infrared sensors were designed and fabricated.The response speed is reduced from 1200 ms to 50 ms.Furthermore,both N-type and P-type multi-walled carbon nanotube arrays were achieved by chemical vapor deposition method.Based on the carbon nanotube P-N junction,new type of infrared sensor was presented.The infrared sensor responsivity was increased from 2.25×10^-3 V/W to 1.05×10^-2 V/W.As demonstration,week thermal radiation from human body was successfully detected.?2?Design and fabrication of single-walled carbon nanotube based micro-pressure sensors.To improve the sensitivity of pressure sensors,a high performance micro-pressure sensor with sensitivity of 8655.6 kPa^-1 was fabricated by integrating pyramid microstructure arrays with single-walled carbon nanotube conductive layer.Finally,we demonstrated its potential applications in electronic skin and human pulse detection.?3?Design and fabrication of multi-layered,stretchable integrated circuit system with high-density chip integration.At present,all the reported stretchable circuits are single.To increase the chip density,with silicone materials improvement,laser selective etching and aligned transfer printing techniques,fabrication protocol for multi-layered stretchable circuit was presented.For the demonstration,we successfully fabricated a 4-layer multifunctional stretchable circuit.The system can achieve 35%stretchability in horizontal direction and 50%stretchability in vertical direction.?4?Design and fabrication of biological potential sensors,and integrated with stretchable circuit system for health care and human-machine interface.At present,there is no report that combines high-performance soft sensors with structure-based stretchable circuit system for practical application.Autonomous system,that can be used for wireless health care and human-machine interface,was built by integrating the carbon nanotubes based biological potential sensors with stretchable circuit system.It can monitor human epidermal potential?ECG,EMG,EOG and EEG?,breath,skin temperature and motion state wirelessly.Furthermore,the system can be attached on human forearm for the control of robot arm.With wireless communication,the robot arm can follow the exact movements of human arm.