Flexible Single‐Substrate Integrated Active‐Matrix Pyroelectric Sensor

Abstract

Recently developed flexible active matrix sensors employ organic and large area electronics to enable artificial sensing skin applications. In the proof‐of‐concept presented here, an active matrix proximity sensor‐array is formed by monolithic integration of screen‐printed sensors with organic transistors on a single sheet of a polymer film, using only seven industrially scalable patterning steps. A ferroelectric co‐polymer of polyvinylidendifluoride (PVDF) serves as the pyro‐sensor material, and bottom‐gate top‐contact organic thin film transistors switch the sensors during operation. An on/off ratio well above 103 and a low off‐current below 8 × 10−11 A of the organic transistors result in a dynamic range of 44 dB and allow to detect a human hand approaching to a distance of 20 cm with a signal‐to‐noise ratio of 28 dB. A basic matrix operation is demonstrated by the correct tracking of a moving human hand.

Heterogeneous Functional Dielectric Patterns for Charge‐Carrier Modulation in Ultraflexible Organic Integrated Circuits

“…PNDPE layers have already been used in previous studies as the gate dielectric in p-and n-channel based OTFTs. [16,37,38] However, in these studies, either rigid glass substrates or very thick PNDPE layers as much as a few µm were used; in addition, ICs were not fabricated. This study demonstrates the HFDP for V th control in OTFTs on the same substrate for high-performance ICs with the use of ultrathin PNDPE gate dielectrics.…”

“…Flexible electronic devices often require integrated circuits (ICs) for signal processing; thus, the development of flexible ICs is crucial in the practical applications of flexible electric devices.Organic thin-film transistors (OTFTs) are attractive candidates in the development of flexible ICs because they can be fabricated on flexible, and even stretchable substrates, with low-cost and largearea fabrication processes. [16][17][18] Their individual electric properties have been analyzed and reported over the past few decades, focusing on threshold voltage (V th ), [19][20][21][22][23][24][25][26][27][28] mobility, [29][30][31] and stability, [32,33] which were primarily controlled or improved by modulating the behavior of charge carriers at the interface between the gate dielectrics and semiconductors. Particularly, V th is one of the key characteristics which affects the performance of the ICs considering that in the early stages the silicon-based ICs was produced using only V th controlled n-channel transistors.…”

Ultrasensitive electrolyte-assisted temperature sensor

“…A change in temperature affects the self-polarization over the pyroelectric material, leading to electrical currents to compensate for those changes [19][20][21] . However, pyroelectric signals are transient and quickly decay to zero after a change in temperature has taken place, which is not suitable for long-term temperature monitoring [22][23][24][25] . By contrast, recently developed ionic thermoelectric sensors 26 can provide self-generated open-circuit voltages that are stable over time.…”

Organic Thin Film Transistors in Mechanical Sensors

“…[ 124 ] The work demonstrates a lightweight, effective, low cost device using a few common materials and a straightforward approach. This work then spurred much of the research described here in flexible piezoelectric transistor arrays for sensing, including a recent work by Gold et al [ 144 ] Presented as a proof of concept, the pyroelectric effect of PVDF‐TrFE is leveraged in this work to measure proximal human motion between 5 and 20 cm away with a high signal to noise ratio of 28 dB. The device has a 3x3 sensor matrix, where an active matrix approach is used to observe the response of a specific sensing capacitor.…”

“…[ 125 ] In some active matrix arrays, the transistors are simply used to address a specific piezoelectric capacitor for sensing. [ 124,143,144 ] In this case, the piezoelectric element is connected to the source or drain of one transistor in the active matrix and the piezoelectric response is read out when that transistor is activated. In this approach, there is no immediate amplification of the charge, and any needed amplification will have to be added in off‐chip electronics.…”