Self-powered electro-tactile system for virtual tactile experiences

Abstract

Tactile sensation plays important roles in virtual reality and augmented reality systems. Here, a self-powered, painless, and highly sensitive electro-tactile (ET) system for achieving virtual tactile experiences is proposed on the basis of triboelectric nanogenerator (TENG) and ET interface formed of ball-shaped electrode array. Electrostatic discharge triggered by TENG can induce notable ET stimulation, while controlled distance between the ET electrodes and human skin can regulate the induced discharge current. The ion bombardment technique has been used to enhance the electrification capability of triboelectric polymer. Accordingly, TENG with a contact area of 4 cm² is capable of triggering discharge, leading to a compact system. In this skin-integrated ET interface, touching position and motion trace on the TENG surface can be precisely reproduced on skin. This TENG-based ET system can work for many fields, including virtual tactile displays, Braille instruction, intelligent protective suits, or even nerve stimulation.

Fig. 1. Skin-integrated ET interface.

(A) Schematic illustration of the ET system to transmit virtual spatial pattern. (B) Exploded view of the electrode array. (C) ET sense of the ET system (controlled distance, 0.4 mm). (D) Optical images of the electrode array (scale bar, 10 mm). The inset shows an enlarge view of a ball electrode (Φ = 0.5 mm). (E) Image of the TENG array (21 units sized in 20 × 20 mm; center-to-center distance, 40 mm; scale bar, 20 mm). Photo credit: Fan Wang, Chinese Academy of Sciences.

Fig. 2. Working mechanism and optimized electric outputs of ET interface.

(A) Schematic diagram of ET stimulation powered by TENG. (B) Open-circuit transferred charge of friction between various positive tribomaterials [Kapton, PET, polyethylene naphthalate (PEN), ion-bombarded PEN (II-PEN), and ion-bombarded Kapton (II-Kapton)] with PTFE (effective tribo-area: 20 × 20 mm). (C) Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectra of the pristine Kapton film and II-Kapton (ion dose of 1 × 10¹⁶/cm², 50 keV). arb. units, arbitrary units. (D) Scanning electron microscopy (SEM) images of Kapton and II-Kapton (scale bar, 2 μm). (E) Discharging current (I_d) and transferred charge (Q_d) in the process of (A) with an inset image of the discharge on skin (controlled distance, 0.5 mm; TENG sized 20 × 20 mm). (F) I_d and Q_d in numbers of friction circle. (G) Simulated charge threshold of ball-plate electrode under different controlled distances (air breakdown voltage, 30 kV/cm; ball electrode, Φ = 0.5 mm; and plate electrode, 0.1 × 10 mm). Photo credit: Yuxiang Shi, Chinese Academy of Sciences.

Fig. 3. Noninterference and influential factors test of ET interface.

(A) Path of II-Kapton sliding from electrodes 2 to 21. (B) Open-circuit voltages of TENG array when II-Kapton moves from 2 to 21. (C) A superimposed image of the discharge induced by the sliding II-Kapton. (D) Mapping figures of open-circuit voltage when II-Kapton arrives at the center of an electrode. (E) Transferred charges (Q_d) of discharging at various controlled distances (0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 1.0, 1.2, and 1.5 mm). (F) Amount of Q_d when discharging on ball electrode of different curvatures (0.15, 0.2, 0.225, 0.25, 0.25, 0.275, 0.3, 0.325, and 0.38 mm). (G) Q_d amount (discharging at controlled distance of 0.3, 0.5, and 0.8 mm) of the stretchable electrode when strained (0 and 100%). Photo credit: Yuxiang Shi, Chinese Academy of Sciences.

Fig. 4. An example of ET interface applied for enhancing tactile VR experience of precepting virtual spatial patterns (random figures).

(A) Image when a girl facilitated with ET interface is accepting the test. (B) Schematic diagram of the test including generating random figure, imputing signaling through TENG array, ET stimulating by wearable electrode array, and giving feedback. Photo credit: Jingwen Tian, Chinese Academy of Sciences.

Fig. 5. An integrated ET system.

(A to C) The structure of an ET unit (A), optical image of the system fabricated in semicylinder (B), and illustration when integrated on forearm (C). (D and E) The discharging current (D) and transferred charges (E) of the ET system unit. (F) Schematic diagram of positive-pressure protective suit (I) and spacesuit (II) equipped with the ET system (the shaded location), respectively. Photo credit: Jingwen Tian, Chinese Academy of Sciences.