Artificial Merkel discs in van der Waals heterostructures for bio-inspired tactile sensing

Abstract

Mechanoreceptors, such as Merkel discs in the somatosensory system, play a crucial role in converting mechanical stimuli into electrical signals, enabling spatial discrimination and perception. This study investigates a conventional van der Waals heterostructures field-effect transistor (VHFET) with strategically positioned access regions (AR) to mimic unique neuronal behaviors. The neuronal VHFET with AR (VHFET-AR) device, constructed using 2D materials including molybdenum disulfide as the channel, hexagonal boron nitride as the tunneling insulator, and graphene as the floating gate, functions as a synaptic device designed to replicate the role of Merkel discs in human skin. The VHFET-AR device successfully reproduces fundamental nervous system functions, including spike amplitude-dependent plasticity, spike duration-dependent plasticity, spike number-dependent plasticity, and slow adaptation (SA). It further demonstrates long-term potentiation and depression modulated by spike intervals, exhibiting synaptic plasticity similar to that of biological systems. Unlike complex and bulky electronic circuits, the VHFET-AR device can perform inverse notch signaling and lateral inhibition at a frequency of approximately 11.23 Hz, closely aligning with the low-frequency stimuli (5–15 Hz) characteristic of biological Merkel discs, which are essential for spatial localization and discrimination. The compact design of the VHFET-AR device highlights its merit in minimizing the size of the electronic circuit. By incorporating properties such as inverse notch signaling, lateral inhibition, and SA, the VHFET-AR device represents a significant advancement in developing artificial mechanoreceptor hardware, offering a closer emulation of the complex mechanisms underlying the biological somatosensory system.