Development Of Stretchable Near-infrared Phototransistor Sensor Chip

Stretchable electronics,as the future growing trend of flexible electronics,have broad application prospects and commercial value in fields of biomedicine,public health,entertainment,education and manufacturing industry.There is no doubt that the development of stretchable electronics is unsustainable without various sensors.Among them,the photoelectric sensor has some advantages such as non-invasiveness,fast response and easy adjustment,quite suitable for the detections of physiological signals on the human body surface.However,most of traditional photoelectric sensors have some disadvantages such as rigidity,poor adhesion and poor environmental adaptability.Thus,they cannot satisfy the requirements of multi-application scenarios.In this paper,the organic photosensitive transistor was used as the basic structure of the photoelectric sensor.We deeply studied implement methods on the stretchabilities of dielectric layer,substrate,electrode and organic semiconductor layer.Finally a stretchable near-infrared photosensitive transistor sensor chip was successfully developed.In a stretching range of 20%,the device shows high sensitivity of photoelectric detection sensitivity and good operation stability.The main contents of this paper are as follows:1.In this work,the doping effect of lithium bis(fluorosulfonyl)imide on performance of the dielectric layer of the organic phototransistor was investigated.We prepared a lithium salt-containing ionogel dielectric layer by blending polymer cross-linking agent,ionic liquid and lithium bis(fluorosulfonyl)imide.The doping effect of lithium salt on capacitance and stretchability of the ionogel dielectric layer,were comparatively studied by electrical and mechanical characterization methods.The results show that the unit of capacitance of the lithium salt-containing ionogel dielectric layer reaches 2.6?F?cm^-2 at 100 Hz.Compared with that case without lithium salt,the value increases by more than 100%,and the capacitance change rate is as low as 1%under 50%strain.A near-infrared photosensitive transistor constructed by the lithium salt-containing ionogel dielectric,showing a high photo detection sensitivity of about 10⁴ in gate dielectric layer stretching range of 100%.2.In this work,we systematically studied the implement methods of the stretchabilities of substrate,electrode and organic semiconductor layer of the near-infrared phototransistor.An insulating thermoplastic elastomer SEBS was used to fabricate the high stretchability insulating substrate film by a solution method.The source,drain and gate electrodes with snake-like structure in the stretchable near-infrared phototransistor were designed and fabricated into snakelike structure.We proposed to blend a certain proportion of insulating polymer into the organic semiconductor active layer of the phototransistor.Due to nanoconfinement effect,the stretchability of the active layer after optimization was greatly improved.On these bases,a stretchable near-infrared phototransistor sensor was successfully developed.Without stretching,charge mobility in the transistor reaches 0.12 cm²?V^-1?s^-1,which shows good transistor response characteristic.The photo detection sensitivity of the device reaches 200,and the sensitivity is still maintained at about 100 under stretching of 20%.3.In this work,we developed a wearable system for non-invasive,real-time and dynamic detection on pulse signals.With this system,the flexible near-infrared phototransistor was successfully used to detect the pulse signal which was involving of a main wave and a dicrotic pulse wave.The results lay a foundation for realizing the physiological signal detection system based on the stretchable near-infrared phototransistor sensor in the future.