Synapses are essential to the transmission of nervous signals. Synaptic plasticity allows changes in synaptic strength that make a brain capable of learning from experience. During development of neuromorphic electronics, great efforts have been made to design and fabricate electronic devices that emulate synapses. Three‐terminal artificial synapses have the merits of concurrently transmitting signals and learning. Inorganic and organic electronic synapses have mimicked plasticity and learning. Optoelectronic synapses and photonic synapses have the prospective benefits of low electrical energy loss, high bandwidth, and mechanical robustness. These artificial synapses provide new opportunities for the development of neuromorphic systems that can use parallel processing to manipulate datasets in real time. Synaptic devices have also been used to build artificial sensory systems. Here, recent progress in the development and application of three‐terminal artificial synapses and artificial sensory systems is reviewed.
We
fabricated a nanowire-channel intrinsically stretchable neuromorphic
transistor (NISNT) that perceives both tactile and visual information
and emulates neuromorphic processing capabilities. The device demonstrated
excellent stretching endurance of 1000 stretch cycles while retaining
stable electrical properties. The device was then applied as a multisensitive
afferent nerve that processes information in parallel. Compatible
with skin deformation, the devices are attached to fingers to serve
as conformal strain sensors and neuromorphic information-processing
units for gesture recognition. The excitatory postsynaptic current
in each device represents shape changes and is then analyzed using
softmax activation processing of the neural network to recognize gestures.
A multistage neural network that uses NISNT was used to further confirm
the gestures. This work demonstrated an idea toward multisensory artificial
nerves and neuromorphic systems.
A graphdiyne-based artificial synapse (GAS), exhibiting intrinsic short-term plasticity, has been proposed to mimic biological signal transmission behavior. The impulse response of the GAS has been reduced to several millivolts with competitive femtowatt-level consumption, exceeding the biological level by orders of magnitude. Most importantly, the GAS is capable of parallelly processing signals transmitted from multiple pre-neurons and therefore realizing dynamic logic and spatiotemporal rules. It is also found that the GAS is thermally stable (at 353 K) and environmentally stable (in a relative humidity up to 35%). Our artificial efferent nerve, connecting the GAS with artificial muscles, has been demonstrated to complete the information integration of pre-neurons and the information output of motor neurons, which is advantageous for coalescing multiple sensory feedbacks and reacting to events. Our synaptic element has potential applications in bioinspired peripheral nervous systems of soft electronics, neurorobotics, and biohybrid systems of brain–computer interfaces.
Polycrystalline organometal halide perovskite films have been recently exploited as the active layer in artificial synapses, demonstrating the basic functional emulation of biological synapses. However, for the implementation of neuromorphic computing and bioinspired intelligent systems, full synapse-like functionality with a simple structure and extremely low energy consumption are of crucial importance. Here, a modified thickness-confined surfactant-assistant self-assembly strategy is proposed to synthesize CH 3 NH 3 PbBr 3 single-crystalline thin platelets (SCTPs) and a two-terminal lateral-structured synaptic device with ultralow operating current down to sub-pA is fabricated. Essential synaptic behaviors are realized, including paired-pulse facilitation, spike-dependent plasticity, transition from sensory memory to short-term memory and potentiation/depression. Furthermore, the activity-dependent plasticity is also demonstrated on the SCTP-based artificial synapse, which may enable nociceptors to detect intense external harm. These results provide a new protocol for designing lateral-structured synaptic devices based on hybrid perovskite SCTPs and future neuromorphic bioelectronics.
Artificial synapses (ASs) are electronic devices emulating important functions of biological synapses, which are essential building blocks of artificial neuromorphic networks for brain‐inspired computing. A human brain consists of several quadrillion synapses for information storage and processing, and massively parallel computation. Neuromorphic systems require ASs to mimic biological synaptic functions, such as paired‐pulse facilitation, short‐term potentiation, long‐term potentiation, spatiotemporally‐correlated signal processing, and spike‐timing‐dependent plasticity, etc. Feature size and energy consumption of ASs need to be minimized for high‐density energy‐efficient integration. This work reviews recent progress on ASs. First, synaptic plasticity and functional emulation are introduced, and then synaptic electronic devices for neuromorphic computing systems are discussed. Recent advances in flexible artificial synapses for artificial sensory nerves are also briefly introduced. Finally, challenges and opportunities in the field are discussed.
Aberrant splicing is frequently found in cancer, yet the biological consequences of such alterations are mostly undefined. Here we report that the Hippo–YAP signalling, a key pathway that regulates cell proliferation and organ size, is under control of a splicing switch. We show that TEAD4, the transcription factor that mediates Hippo–YAP signalling, undergoes alternative splicing facilitated by the tumour suppressor RBM4, producing a truncated isoform, TEAD4-S, which lacks an N-terminal DNA-binding domain, but maintains YAP interaction domain. TEAD4-S is located in both the nucleus and cytoplasm, acting as a dominant negative isoform to YAP activity. Consistently, TEAD4-S is reduced in cancer cells, and its re-expression suppresses cancer cell proliferation and migration, inhibiting tumour growth in xenograft mouse models. Furthermore, TEAD4-S is reduced in human cancers, and patients with elevated TEAD4-S levels have improved survival. Altogether, these data reveal a splicing switch that serves to fine tune the Hippo–YAP pathway.
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