Wednesday, April 17, 2024

An Organic Transistor With Dual Sensing And Processing Capabilities

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Researchers at Xi’an Jiaotong University, the University of Hong Kong and Xi’an University of Science and Technology have developed a dual-function organic transistor, both a sensor and processor.

Design of the mode-switchable cv-OECT. a, Comparison between the biological nervous system and cv-OECT-based artificial nervous system, where cv-OECT can act as both volatile receptor and non-volatile synapse. Optical micrographs display the top view of a v-OECT (scale bar, 100 μm). b, Device architecture of v-OECT; the two dashed boxes show the ion contribution in the volatile/non-volatile mode and the chemical structure of PTBT-p, respectively. c, Cryo-EM images of the 200 °C-thermal annealed (TA) and as-cast PTBT-p films. d, Transfer curves of cv-OECT with polarizable/non-polarizable gate electrode. e, Normalized 0–1 absorbance as a function of doping potential; the inset shows the setup for UV–vis measurement. Stages I and II correspond to the doping of amorphous and crystalline regions, respectively. f, Time-resolved UV–vis spectra of channels correspond well with the device performance. g, XPS spectra of as-cast and annealed p-OECT channels doped at LGP and HGP. The pink and blue lines are the signals from [TFSI−] before and after 30 nm etching. h, One-dimensional GIWAXS profile of the annealed film samples. Before measurement, the samples were doped at LGP or HGP and then grounded. Reversible displacement of the (100) peak between the high/low resistance state (HRS/LRS) suggests that the anions firmly embed among the glycol side chains in the crystalline region. i, Schematic explaining the mode-switching mechanism. The special channel dimensions and crystallization provide a high-barrier eVb between the two ionic states (1 and 2), resulting in a non-volatile behavior. Vb denotes the voltage bias that drives the ions to overcome the barrier. LGP can only inject ions into the amorphous regions and lead to volatile behavior. When the non-polarizable gate was used, the counterions cannot be reduced on the gate and thus they migrate into and neutralize the channel because of the reversed electric field, making the device volatile. Credit: Nature Electronics (2023). DOI: 10.1038/s41928-023-00950-y
Design of the mode-switchable cv-OECT. a, Comparison between the biological nervous system and cv-OECT-based artificial nervous system, where cv-OECT can act as both volatile receptor and non-volatile synapse. Optical micrographs display the top view of a v-OECT (scale bar, 100 μm). b, Device architecture of v-OECT; the two dashed boxes show the ion contribution in the volatile/non-volatile mode and the chemical structure of PTBT-p, respectively. c, Cryo-EM images of the 200 °C-thermal annealed (TA) and as-cast PTBT-p films. d, Transfer curves of cv-OECT with polarizable/non-polarizable gate electrode. e, Normalized 0–1 absorbance as a function of doping potential; the inset shows the setup for UV–vis measurement. Stages I and II correspond to the doping of amorphous and crystalline regions, respectively. f, Time-resolved UV–vis spectra of channels correspond well with the device performance. g, XPS spectra of as-cast and annealed p-OECT channels doped at LGP and HGP. The pink and blue lines are the signals from [TFSI] before and after 30 nm etching. h, One-dimensional GIWAXS profile of the annealed film samples. Before measurement, the samples were doped at LGP or HGP and then grounded. Reversible displacement of the (100) peak between the high/low resistance state (HRS/LRS) suggests that the anions firmly embed among the glycol side chains in the crystalline region. i, Schematic explaining the mode-switching mechanism. The special channel dimensions and crystallization provide a high-barrier eVb between the two ionic states (1 and 2), resulting in a non-volatile behavior. Vb denotes the voltage bias that drives the ions to overcome the barrier. LGP can only inject ions into the amorphous regions and lead to volatile behavior. When the non-polarizable gate was used, the counterions cannot be reduced on the gate and thus they migrate into and neutralize the channel because of the reversed electric field, making the device volatile. Credit: Nature Electronics (2023). DOI: 10.1038/s41928-023-00950-y

Electronics engineers strive to create efficient brain-inspired hardware for artificial intelligence (AI) models. Current hardware focuses on sensing, processing, or storing data, but some teams aim to integrate all three functions into one device.

Researchers at Xi’an Jiaotong University, the University of Hong Kong and Xi’an University of Science and Technology have introduced an innovative organic transistor that serves as both a sensor and processor. Traditional AI hardware employs distinct data sensing, processing, and memory storage systems. The separation causes high energy consumption and delays as data is converted between hardware components and analog signals. Pioneering studies emphasize organic electrochemical transistors’ impressive sensing and analog memory abilities (OECTs).

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The researchers aimed to create a dual-function OECT as a sensor and processor to enhance AI hardware efficiency. OECTs are thin film devices that function as transistors, holding promise for smart bioelectronics and neuromorphic hardware. The OECT features distinct sensing and processing modes enabled by selective ion doping of the crystalline-amorphous channel within the device. In the sensing mode, migrating ions driven by a physiological signal enter the crystal structure but can diffuse back, keeping low conductance. In the processing mode, these ions are ‘trapped’ by the crystal structure, maintaining high conductance. This dual functionality enhances the uniqueness and efficiency of our OECT device.

The researchers employed cost-effective techniques like thermal evaporation, solution blade coating, thermal annealing, and reactive ion etching to produce their OECT array, enabling large-scale fabrication. The device is a sensor for diverse signals like electrophysiology, chemicals, light, and temperature. Additionally, as a memory unit, it stores 10-bit analog states, exhibits low switching randomness, and retains states for over 10,000 seconds. Our OECT device is truly versatile in the field of AI. The team conducted experiments to evaluate their device’s ability to switch operating modes. They discovered effective modulation, enabling it to function as a sensor and processor. As a sensor, it detects various stimuli, including ions and light. As a processor, it handles 10-bit analog states while retaining them well.

In the future, this transistor could advance neuromorphic devices for data collection and processing. The researchers demonstrated its real-time cardiac disease diagnosis capability and planned to explore more applications.

Reference: Shijie Wang et al, An organic electrochemical transistor for multi-modal sensing, memory and processing, Nature Electronics (2023). DOI: 10.1038/s41928-023-00950-y

Nidhi Agarwal
Nidhi Agarwal
Nidhi Agarwal is a journalist at EFY. She is an Electronics and Communication Engineer with over five years of academic experience. Her expertise lies in working with development boards and IoT cloud. She enjoys writing as it enables her to share her knowledge and insights related to electronics, with like-minded techies.

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