High-sensitivity pressure sensors are crucial for the ultrasensitive touch technology and E-skin, especially at the tiny-pressure range below 100 Pa. However, it is highly challenging to substantially promote sensitivity beyond the current level at several to 200 kPa and to improve the detection limit lower than 0.1 Pa, which is significant for the development of pressure sensors toward ultrasensitive and highly precise detection. Here, we develop an efficient strategy to greatly improve the sensitivity near to 2000 kPa using short-channel coplanar device structure and sharp microstructure, which is systematically proposed for the first time and rationalized by the mathematic calculation and analysis. Significantly, benefiting from the ultrahigh sensitivity, the detection limit is improved to be as small as 0.075 Pa. The sensitivity and detection limit are both superior to the current levels and far surpass the function of human skin. Furthermore, the sensor shows fast response time (50 μs), excellent reproducibility and stability, and low power consumption. Remarkably, the sensor shows excellent detection capacity in the tiny-pressure range, including light-emitting diode switching with a pressure of 7 Pa, ringtone (2-20 Pa) recognition, and ultrasensitive (0.1 Pa) electronic glove. This work represents a performance and strategic progress in the field of pressure sensing.

Pressure sensor is one of the most fascinating and important components of E-skin that possesses unique abilities to imitate, enhance, and replace the human's tactile sensation. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] Among the different kinds of pressure sensors, [17][18][19][20][21][22][23][24][25][26][27][28][29][30] piezoresistive sensors generally have simple structures and easy read-out characteristics, which make them highly promising for application. [31][32][33][34] However, on the other hand, the simple output signal (current or resistance) presents difficulty to identify the complex and multiple stimuli. As for the organic field-effect transistor (OFET)-based sensors, the unique current amplification function of transistor makes it ideal candidate for sensing weak signals, and their multiple output parameters (source-drain current, threshold voltage, current on/off ratio, subthreshold swing) enable it to distinguish complex signals. [35][36][37] Furthermore, every component of OFETs including gate electrode, dielectric layer, semiconductor layer, and drain/source electrodes can be probably used as active layer of sensors, [38,39] which provides more possibilities for integration of multiple sensing. [40][41][42][43][44] In some reported sensors, tuning dielectric capacitance of OFET by pressure is mainly used as the basic working principle. Bao and co-workers pioneered in using microstructured poly(dimethylsiloxane) (PDMS) as dielectric of OFET for sensing pressure with sensitivity of 0.55 kPa −1 . [22] Zhu and co-workers utilized a suspended gate for construction of pressure sensor with sensitivity of 192 kPa −1 . [30] However, the tuning of capacitance in OFET may suffer from the risk of impurity or breakdown. As stated above, all components of OFET might be used for the pressure sensors, but OFET-based pressure sensors using semiconductor and source/ drain electrodes have not been reported so far.In OFETs, the contact interface between semiconductor and source/drain electrodes determines the charge injection efficiency and thus greatly influences the device performance, which therefore provides a model for pressure sensing if the contact quality can be tuned by pressure with an appropriate device structure. Piezoresistive sensor with roughened contact interface provides inspiration, but the active components of conventional piezoresistive sensor generally consist of one or more kinds of conducting materials since the low bulk resistivity of conducting materials may enable the contact resistance to dominate the sensor device and therefore produce The piezoresistive pressure sensor, a kind of widely investigated artificial device to transfer force stimuli to electrical signals, generally consists of one or more kinds of conducting materials. Here, a highly sensitive pressure sensor based on the semiconductor/conductor interface piezoresistive effect is successfully demonstrated by using organic transistor geometry. Because of the efficient combination of the piezoresistive effect and f...

Ultrathin film with thickness below 15 nm of organic semiconductors provides excellent platform for some fundamental research and practical applications in the field of organic electronics. However, it is quite challenging to develop a general principle for the growth of uniform and continuous ultrathin film over large area. Dip-coating is a useful technique to prepare diverse structures of organic semiconductors, but the assembly of organic semiconductors in dip-coating is quite complicated, and there are no reports about the core rules for the growth of ultrathin film via dip-coating until now. In this work, we develop a general strategy for the growth of ultrathin film of organic semiconductor via dip-coating, which provides a relatively facile model to analyze the growth behavior. The balance between the three direct factors (nucleation rate, assembly rate, and recession rate) is the key to determine the growth of ultrathin film. Under the direction of this rule, ultrathin films of four organic semiconductors are obtained. The field-effect transistors constructed on the ultrathin film show good field-effect property. This work provides a general principle and systematic guideline to prepare ultrathin film of organic semiconductors via dip-coating, which would be highly meaningful for organic electronics as well as for the assembly of other materials via solution processes.