An artificially-intelligent cornea with tactile sensation enables sensory expansion and interaction

Abstract

We demonstrate an artificially-intelligent cornea that can assume the functions of the native human cornea such as protection, tactile perception, and light refraction, and possesses sensory expansion and interactive functions. These functions are realized by an artificial corneal reflex arc that is constructed to implement mechanical and light information coding, information processing, and the regulation of transmitted light. Digitally-aligned, long and continuous zinc tin oxide (ZTO) semiconductor fabric patterns were fabricated as the active channels of the artificial synapse, which are non-toxic, heavy-metal-free, low-cost, and ensure superior comprehensive optical properties (transmittance >99.89%, haze <0.36%). Precisely-tuned crystal-phase structures of the ZTO fibers enabled reconfigurable synaptic plasticity, which is applicable to encrypted communication and associative learning. This work suggests new strategies for the tuning of synaptic plasticity and the design of visual neuroprosthetics, and has important implications for the development of neuromorphic electronics and for visual restoration.

Fig. 1. Overview of an artificial corneal reflex arc.

Schematic of the corneal reflex and the corresponding artificial corneal reflex arc composed of sensor-oscillation circuits, ZTO ASs, and electrochromic devices.

Fig. 2. Digitally-aligned ZTO fibers with tunable crystal structure.

a Schematic of a biological synapse. b AS that uses ZTO fibers. c aEPSC of ZTO-3:7 AS triggered by a single spike. d, e SEM images of ZTO-3:7 fibers array (d) and a single fiber (e). f Cross-sectional analysis of a single ZTO-3:7 fiber. Inset: AFM image of a single ZTO-3:7 fiber. g HRTEM image of ZTO-3:7 fibers. Inset: SAED pattern of ZTO-3:7 fibers. h XRD pattern of ZTO-3:7 fibers. i O 1 s XPS spectra of ZTO-3:7 fibers. j, k Visible-range transmittance (j) and haze (k) of ZTO-3:7 fibers with different patterns and pitch sizes. Inset: OM images of the ZTO fibers. l Transmittance (at wavelength 550 nm) versus haze for ZTO-3:7 fibers and other materials. m Optimized structure of ZTO-3:7 fibers. n Energy band structure of ZTO-3:7 fibers. o DOS of ZTO-3:7 fibers. The Fermi level is set to zero.

Fig. 3. ZTO-fibers artificial synapses with tunable synaptic plasticity.

a, b Schematic illustration of synaptic signal conduction under a pair of stimuli: biological synapse (a) and ZTO-fibers AS (b). c aEPSC of ZTO-3:7 AS evoked by a pair of spikes. d PPF index versus spike interval for three ZTO ASs with different Zn:Sn molar ratios. e, f aEPSC of ZTO-3:7 AS (e) and ΔaEPSC of three ZTO ASs with different Zn:Sn molar ratios (f) triggered by consecutive spikes with different spike numbers. g aEPSC of ZTO-3:7 AS triggered by consecutive spikes with different spike frequencies. h aEPSC gain versus frequency for three ZTO ASs with different Zn:Sn molar ratios. i, j aEPSC (i) and ΔaEPSC (j) triggered by spikes with different spike duration for three ZTO ASs with different Zn:Sn molar ratios. k aEPSC of ZTO-3:7 AS triggered by spikes with different amplitude. l International Morse code of “NKU” and “YES” realized using ZTO-1:1 AS. m Pavlovian learning behavior realized using ZTO-3:7 AS.

Fig. 4. An artificially-intelligent cornea with tactile sensation.

a Schematic of corneal reflex examination (left), and the process of corneal reflex (right). b Schematic of corneal reflex evoked by mechanical stimuli. c Configuration of artificial corneal reflex arc responding to mechanical stimuli. d Schematic of the structure of the electrochromic device. e, f Digital images (e) and optical transmittance spectra (f) of the electrochromic device under different stimulation voltages. g Refractive index and extinction coefficient of the electrochromic device under different stimulation time. h Schematic illustration of the Li⁺ ions and charge transportation through the electrochromic device. i Digital images of electrochromic actuators under bilateral reflex (I), without reflex (II), ipsilateral reflex (III), and contralateral reflex (IV).

Fig. 5. Sensory expansion and interactive functions of the artificially-intelligent cornea.

a Schematic of the light perception in the human eyes. b Schematic of a robot equipped with an artificially-intelligent cornea. c Configuration of the artificial corneal reflex arc responding to light stimuli. d Frequency of the output spikes from light sensor-oscillation circuit versus illuminance. e Statistical curve of signal output over time for each part of the artificially-intelligent cornea under light stimulation. f, g Digital images of an electrochromic actuator and the corresponding schematic of the human eye under weak light (f) and bright light (g). h Digital images of a robot equipped with an artificially-intelligent cornea.