New human–machine interface material is imperceptible to wearers

Written by Ilana Landau, Editor

A new, wearable, human–machine interface (HMI) has been devised that can be worn with minimal user irritation; the technology may even be useful as synthetic skin.

Wearable, human–machine interfaces (HMIs) represent a key method of collecting health data about wearers and engaging patients. However, these wearable HMIs are frequently large, uncomfortable and mechanically restrictive for wearers, exhibiting slow responses. Now, due to advances in materials and mechanical designs, researchers at the University of Houston (TX, USA) have developed an HMI that combats these common challenges associated with conventional devices.

HMIs assess variations in users’ physical or electrophysiological parameters. This transduced information is used to drive specific machine functions.

Development of ideal HMIs has been limited by the materials available for their construction; semisoft wearables are uncomfortable and restrictive for users whilst deformable, soft, elastic devices display sluggish response times. Further, inorganic HMI materials pose challenges for the design of devices that can carry out several functions — such as sensing, switching, stimulation and data storage.

Now, researchers have developed a multifunctional, ultra-thin HMI device that allows wearers to move naturally; the technology may even be employable as a synthetic skin for robotic limbs, achieving a ‘closed-loop’ system.

The novel device utilizes a sol-gel-on-polymer—processed, indium zinc oxide, semiconductor nanomembrane. This is combined with a stretchable, resistive, random-access memory (ReRAM), field-effect transistors and sensors for temperature, ultraviolet and strain.

Together, these simultaneously-constructed, individual components are encased in an ultrathin — approximately 3.5 micron — meandering, open-mesh configuration. This allows for the device to be wearer-imperceptible and flexible.

In the study, the authors stated: “The ultrathin stretchable and imperceptible electronics-enabled wearable sensors, prosthetic skin, and an actuator device for humans and robotics prove the feasibility of a closed-loop HMI system.”

The authors concluded: “Such a type of stretchable device paves the way toward low-cost, scalable manufacturing, wearable HMI devices capable of seamless and robust interfacing with the wearer. In addition, it also enables the wearable HMI device to become a vital technology with enhanced capabilities, comfort, and convenience toward enhanced interaction and teaming between humans and machines.”


Sim K, Rao Z, Zu Z et al. Metal oxide semiconductor nanomembrane—based soft unnoticeable multifunctional electronics for wearable human-machine interfaces. Sci. Adv. 5(8); eaav9653 (2019);