Metal oxide semiconductor nanomembrane-based soft unnoticeable multifunctional electronics for wearable human-machine interfaces

Abstract

Wearable human-machine interfaces (HMIs) are an important class of devices that enable human and machine interaction and teaming. Recent advances in electronics, materials, and mechanical designs have offered avenues toward wearable HMI devices. However, existing wearable HMI devices are uncomfortable to use and restrict the human body's motion, show slow response times, or are challenging to realize with multiple functions. Here, we report sol-gel-on-polymer-processed indium zinc oxide semiconductor nanomembrane-based ultrathin stretchable electronics with advantages of multifunctionality, simple manufacturing, imperceptible wearing, and robust interfacing. Multifunctional wearable HMI devices range from resistive random-access memory for data storage to field-effect transistors for interfacing and switching circuits, to various sensors for health and body motion sensing, and to microheaters for temperature delivery. The HMI devices can be not only seamlessly worn by humans but also implemented as prosthetic skin for robotics, which offer intelligent feedback, resulting in a closed-loop HMI system.

Fig. 1. Ultrathin, stretchable, mechanically imperceptible, multifunctional HMI device for human and robotics.

(A) Schematic exploded view of an ultrathin multifunctional HMI device. (B) Optical image of the device on a human forearm. Inset is a magnified image. (C) SEM image of the device on a piece of replicated skin. (D) Optical images of the device on a human skin under mechanical deformation: compressed (left) and stretched (right). (E) Schematic exploded view of the temperature sensor array for the robotic hand. (F) Optical image of the temperature sensor array on a robotic hand. Inset is a magnified image. (G) SEM images of the temperature sensor array. (H) Optical images of the temperature sensor array on the robotic hand under mechanical deformation: bent (left) and stretched (right). Photo credit: Kyoseung Sim, University of Houston.

Fig. 2. Characteristics of the ReRAM and FETs.

(A) Schematic exploded view of the IZO nanomembrane–based ReRAM. (B) Optical microscopic image of the ReRAM. (C) I-V characteristics of the bipolar switching of the ReRAM. (D) WRER cycle of the ReRAM. (E) Sequential images of the IZO nanomembrane–based ReRAM under strain and corresponding FEA results of IZO. (F) Current at LRS and HRS and I_LRS/I_HRS under strain. (G) Schematic exploded view of the IZO FET. (H) Optical microscopic image of the FET. (I) Output characteristics of the FET. (J) Transfer characteristics of the FET. (K) Sequential images of the FETs under strain and corresponding FEA results of IZO. (L) Calculated field-effect mobility of the IZO and I_ON/I_OFF of the FET under strain.

Fig. 3. Characteristics of UV and temperature sensors.

(A) Schematic exploded view of the IZO nanomembrane–based UV sensor. (B) Optical microscopic image of the UV sensor. (C) I-V characteristics of the UV sensor. (D) Calibration curve of the IZO UV sensor. (E) Sequential images of the UV sensor under strain and corresponding FEA results of IZO. (F) I_UV/I_dark for UV light under strain. (G) Schematic exploded view of the IZO temperature sensor. (H) Optical microscopic image of the temperature sensor. (I) Calibration curve of the temperature sensor. (J) Plot of lnR versus 1000/T of the temperature sensor. (K) Sequential images of the IZO temperature sensor under strain and corresponding FEA results of IZO. (L) Relative resistance change of the temperature sensor under strain.

Fig. 4. Characteristics of strain sensor.

(A) Schematic exploded view of the IZO strain sensor. (B) Optical microscopic image of the strain sensor. (C) Calibration curve of the strain sensor. (D) Relative resistance change of the strain sensor under cyclic stretching and relaxing. (E) Sequential images of the strain sensor under strain and corresponding FEA results of IZO.

Fig. 5. Wearable closed-loop HMI.

(A) Representative image of human motion to control the robotic hand. (B) Resistance change of strain sensor on the human skin under different human motions. (C) Representative image of human motion mimicking. (D) Resistance change of strain sensor on human motion mimicking. (E) Representative image of the robotic hand, with the temperature sensor touching the human hand. (F) Resistance change of the temperature sensor on the robotic hand while human hand holds the robot. (G) Schematic exploded view of the resistive microheater. (H) IR temperature mapping of the microheater. (I) Dynamic temperature change under different applied voltages. (J) Calibration curve of the microheater. Photo credit: Kyoseung Sim, University of Houston.