The human somatosensory system, consisting of receptors, transmitters, and synapses, functions as the medium for external mechanical stimuli perception and sensing signal delivery/processing. Developing sophisticated artificial sensory synapses with a high performance, uncomplicated fabrication process, and low power consumption is still a great challenge. Here, a piezotronic graphene artificial sensory synapse developed by integrating piezoelectric nanogenerator (PENG) with an ion gel-gated transistor is demonstrated. The piezopotential originating from PENG can efficiently power the synaptic device due to the formation of electrical double layers at the interface of the ion gel/ electrode and ion gel/graphene. Meanwhile, the piezopotential coupling is capable of linking the spatiotemporal strain information (strain amplitude and duration) with the postsynaptic current. The synaptic weights can be readily modulated by the strain pulses. Typical properties of a synapse including excitation/inhibition, synaptic plasticity, and paired pulse facilitation are successfully demonstrated. The dynamic modulation of a sensory synapse is also achieved based on dual perceptual presynaptic PENGs coupling to a single postsynaptic transistor. This work provides a new insight into developing piezotronic synaptic devices in neuromorphic computing, which is of great significance in future self-powered electronic skin with artificial intelligence, a neuromorphic interface for neurorobotics, human-robot interaction, an intelligent piezotronic transistor, etc.

Low power electronics endowed with artificial intelligence and biological afferent characters are beneficial to neuromorphic sensory network. Highly distributed synaptic sensory neurons are more readily driven by portable, distributed, and ubiquitous power sources. Here, we report a contact-electrification-activated artificial afferent at femtojoule energy. Upon the contact-electrification effect, the induced triboelectric signals activate the ion-gel-gated MoS2 postsynaptic transistor, endowing the artificial afferent with the adaptive capacity to carry out spatiotemporal recognition/sensation on external stimuli (e.g., displacements, pressures and touch patterns). The decay time of the synaptic device is in the range of sensory memory stage. The energy dissipation of the artificial afferents is significantly reduced to 11.9 fJ per spike. Furthermore, the artificial afferents are demonstrated to be capable of recognizing the spatiotemporal information of touch patterns. This work is of great significance for the construction of next-generation neuromorphic sensory network, self-powered biomimetic electronics and intelligent interactive equipment.

Several taste transduction mechanisms have been demonstrated in mammals, but little is known about their distribution within and across receptor cells. We recorded whole-cell responses of 120 taste cells of the rat fungiform papillae and soft palate maintained within the intact epithelium in a modified Ussing chamber, which allowed us to flow tastants across the apical membrane while monitoring the activity of the cell with a patch pipette. Taste stimuli were: 0.1 M sucrose, KCl, and NH 4 Cl, 0.032 M NaCl, and 3.2 mM HCl and quinine hydrochloride (QHCl). When cells were held at their resting potentials, taste stimulation resulted in conductance changes; reversible currents Ͼ5 pA were considered reliable responses. Sucrose and QHCl produced a decrease in outward current and membrane conductance, whereas NaCl, KCl, NH 4 Cl, and HCl elicited inward currents accompanied by increased conductance.Combinations of responses to pairs of the four basic stimuli (sucrose, NaCl, HCl, and QHCl) across the 71-84 cells tested with each pair were predictable from the probabilities of responses to individual stimuli, indicating an independent distribution of sensitivities. Of 62 cells tested with all four basic stimuli, 59 responded to at least one of the stimuli; 16 of these (27.1%) responded to only one, 20 (33.9%) to two, 15 (25.4%) to three, and 8 (13.6%) to all of the basic stimuli. Cells with both inward (Na ϩ ) and outward (K ϩ ) voltage-activated currents were significantly more broadly tuned to gustatory stimuli than those with only inward currents. Key words: taste receptor cell; tongue epithelium; palate epithelium; gustatory sensitivity; breadth of tuning; sucrose; quinine; salt; acid; pattern codingTaste transduction involves a variety of mechanisms, including direct permeation or block of ion channels and activation of metabotropic and ionotropic receptors (for review, see Lindemann, 1996;Herness and Gilbertson, 1999). There is little information, however, about how these mechanisms are distributed within and across taste receptor cells. Intracellular recording experiments have suggested that taste cells are broadly responsive to stimuli representing different taste qualities (Kimura and Beidler, 1961;Ozeki and Sato, 1972;Tonosaki and Funakoshi, 1984;Sato and Beidler, 1997). However, because of their relatively small membrane potentials and the possibility of leak currents associated with penetrating such small cells with sharp electrodes, many investigators have viewed these intracellular experiments with skepticism (Kinnamon, 1988;Avenet and Lindemann, 1989;Lindemann, 1996;Herness and Gilbertson, 1999). More recent experiments have used patch-clamp recording methods on isolated taste receptor cells (Avenet and Lindemann, 1987;Akabas et al., 1988;Kinnamon et al., 1988;Gilbertson et al., 1993;Herness and Sun, 1995;Chen et al., 1996;Cummings et al., 1996), but the range of stimuli that can be applied to an isolated cell preparation is limited and recording is hindered by having the apical and basolateral membranes in...