Flexible artificial synapses, which use flexible electronic devices to simulate biological synapses, are the cornerstone of brain‐like computers and artificial intelligence systems. Devices based on field‐effect transistors (FETs) are suitable for emulating synaptic functions because of their diverse material selection, controllable parameters, and clear working mechanism. In addition, owing to their material fabrication and structural design, FETs can realize the special operation mechanisms of devices for constructing flexible artificial synapses with multiple functions. Herein, the essential principles of carrier transport in flexible artificial synapses based on FETs are focused. First, the selection of materials, carrier transfer mechanisms, and synaptic functions of flexible synaptic devices based on various transistors are summarized in detail. Subsequently, the applications of flexible synaptic devices in conformal artificial tactile and visual systems are introduced. Finally, future challenges and opportunities of flexible synaptic devices toward artificial neuromorphic electronics are discussed.

Ambulatory electrocardiography (ECG) is used to realize the diagnostics of coronary heart disease. On-skin electrodes are employed for ambulatory ECG sensing through conformable contact with the arbitrarily shaped moving skin. However, the low skin-adhesion of electrodes limits their application in long-term ambulatory ECG sensing. For example, for the current on-skin electrodes, the low shear viscosity of sweat on the skin decreases the skin-adhesion, leading to their slipping and even falling off. Herein, highly adhesive and washable on-skin electrodes were achieved by combining stretchable Au nanofilms with hybrid materials composed of polydopamine and silk fibroin (SF). The strong interaction of polydopamine with water enhanced the adhesion energy of these electrodes by decreasing the Young's modulus of the SF gel and increasing the contact area between electrodes and skin. Additionally, the microcrack structure of Au nanofilms provided good conductivity upon stretching. Remarkably, our electrodes could be easily removed on washing and had low impedance due to the existence of hydrophilic SF and Ca²⁺. To demonstrate the application of these electrodes for perceiving accurate and reliable signals, they were pasted on the skin to record long-term and high-quality ECG signals for the diagnosis of heart disease.