Emulation of biological synapses is necessary for future brain-inspired neuromorphic computational systems that could look beyond the standard von Neuman architecture. Here, artificial synapses based on ionic-electronic hybrid oxide-based transistors on rigid and flexible substrates are demonstrated. The flexible transistors reported here depict a high field-effect mobility of ≈9 cm V s with good mechanical performance. Comprehensive learning abilities/synaptic rules like paired-pulse facilitation, excitatory and inhibitory postsynaptic currents, spike-time-dependent plasticity, consolidation, superlinear amplification, and dynamic logic are successfully established depicting concurrent processing and memory functionalities with spatiotemporal correlation. The results present a fully solution processable approach to fabricate artificial synapses for next-generation transparent neural circuits.
Highly sensitive and multimodal sensors have recently emerged for a wide range of applications, including epidermal electronics, robotics, health‐monitoring devices and human–machine interfaces. However, cross‐sensitivity prevents accurate measurements of the target input signals when a multiple of them are simultaneously present. Therefore, the selection of the multifunctional materials and the design of the sensor structures play a significant role in multimodal sensors with decoupled sensing mechanisms. Hence, this review article introduces varying methods to decouple different input signals for realizing truly multimodal sensors. Early efforts explore different outputs to distinguish the corresponding input signals applied to the sensor in sequence. Next, this study discusses the methods for the suppression of the interference, signal correction, and various decoupling strategies based on different outputs to simultaneously detect multiple inputs. The recent insights into the materials' properties, structure effects, and sensing mechanisms in recognition of different input signals are highlighted. The presence of the various decoupling methods also helps avoid the use of complicated signal processing steps and allows multimodal sensors with high accuracy for applications in bioelectronics, robotics, and human–machine interfaces. Finally, current challenges and potential opportunities are discussed in order to motivate future technological breakthroughs.
Though
the widely available, low-cost, and disposable papers have
been explored in flexible paper-based pressure sensors, it is still
difficult for them to simultaneously achieve ultrahigh sensitivity,
low limit and broad range of detection, and high-pressure resolution.
Herein, we demonstrate a novel flexible paper-based pressure sensing
platform that features the MXene-coated tissue paper (MTP) sandwiched
between a polyimide encapsulation layer and a printing paper with
interdigital electrodes. After replacing the polyimide with weighing
paper in the MTP pressure sensor, the silver interdigital electrodes
can be recycled through incineration. The resulting pressure sensor
with polyimide or paper encapsulation exhibits a high sensitivity
of 509.5 or 344.0 kPa–1, a low limit (∼1
Pa) and a broad range (100 kPa) of detection, and outstanding stability
over 10 000 loading/unloading cycles. With ultrahigh sensitivity
over a wide pressure range, the flexible pressure sensor can monitor
various physiological signals and human movements. Configuring the
pressure sensors into an array layout results in a smart artificial
electronic skin to recognize the spatial pressure distribution. The
flexible pressure sensor can also be integrated with signal processing
and wireless communication modules on a face mask as a remote respiration
monitoring system to wirelessly detect various respiration conditions
and respiratory abnormalities for early self-identification of opioid
overdose, pulmonary fibrosis, and other cardiopulmonary diseases.
Electronic skins need to be versatile and able to detect multiple inputs beyond simple pressure and touch while having attributes of transparency and facile manufacturability. Herein, we demonstrate a versatile nanostructured transparent sensor capable of detecting wide range of pressures and proximity as well as novel nonoptical detection of printed patterns. The architecture and fabrication processes are straightforward and show robustness to repeated cycling and testing. The sensor displays good sensitivity and stability from 30 Pa to 5 kPa without the use of microstructuration and is conformal and sensitive to be utilized as a wrist-based heart-rate monitor. Highly sensitive proximity detection is shown from a distance of 9 cm. Finally, a unique nonoptical pattern recognition dependent on the difference in the dielectric constant between ink and paper is also demonstrated, indicating the multifunctionality of this simple architecture.
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