Electronic skins (e-skins) are electronic systems that imitate certain features of human skin (e.g., deformability and sensory properties) as realistically as feasible. They are categorized as ‘electronic wearable’–devices worn on, or near, the surface of the skin to extract and analyze information.
Unlike mainstream wearables such as smartwatches, rings or glasses, e-skins are thin, lightweight, and durable. In addition, its material mimics human skin in strength and sensitivity and could collect biological data in real-time.
Grand View Research reported that the e-skin market was worth an estimated $4.5 billion in 2019 and projected a compound annual growth rate of 20.5 percent until 2027.1
Because of its durability, e-skin is a powerful tool for monitoring the elderly, patients with chronic diseases like diabetes or heart conditions, or helps to detect early signs of illness. Thin sensor systems can be embedded into the flexible substrate–typically silicone-based materials with cross-linked polymers–and measure heart rate, levels of blood sugar, tissue pressure, body motion, temperature, metabolites, electrolyte balance, and even brain or muscle signals.
Engineers at the Massachusetts Institute of Technology have developed a sweat-proof “electronic skin”–a conformable, sensor-embedded sticky patch that monitors a person’s health without malfunctioning or peeling away.
Scientists at the National University of Singapore have developed the Tactile Resistive Annularly Cracked E-Skin, or TRACE, a wearable device to measure blood flow in superficial arteries.
Giving prostheses human touch
Amputees often experience the phenomenon of a “phantom limb”–a feeling that a missing body part is still there. To overcome that, engineers at Johns Hopkins University have created an ‘e-dermis’ that will enable amputees to perceive sense through prosthetic fingertips. The device conveys information by stimulating peripheral nerves in the arm, by electrically stimulating the amputee’s nerves through the skin.
Another e-skin, developed at the University of Texas at Arlington, comprises millions of flexible nanowire sensors packaged in a chemical and moisture resistant polyimide. The result is a thin, flexible, self-powered tactile sensing layer, suitable as a robotic or prosthetic skin.
Scientists at the National University of Singapore have developed the Asynchronous Coded Electronic Skin (ACES), an artificial nervous system, that enables robots and prosthetic devices to have a sense of touch equivalent to, or better than, the human skin. ACES can detect touches over 1,000 times faster than the human sensory nervous system. For example, it can differentiate physical contact between different sensors in less than 60 nanoseconds.
Like prosthetics, electronic skins as a sensory surface could enable robots to have a tactile or haptic perception that corresponds to that of humans. An advantage would be the ability to better control the force required when gripping objects. They could improve and simplify human-machine interaction, e.g., thin gloves that transfer finger movements to a robot hand or can be used for gesture control.
E-skin patches could be used as active ingredient depots, where they could release their active ingredient in a time-controlled manner or when they are actually needed. For example, intelligent wound dressings could only release substances that promote healing in those areas where reduced health is detected.
Scientists from the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and the Johannes Kepler University in Linz have developed an electronic sensor that can simultaneously process both touchless and tactile stimuli. That enables the wearer to control both physical and virtual objects, which could provide a seamless interactive platform for virtual and augmented reality scenarios.
The road ahead
The landscape of skin electronics keeps shifting at a spectacular pace. The rise of chronic and non-communicable diseases such as diabetes, cancer, or heart disease will drive the need for health monitoring. As the Internet of Medical Things makes home health care universally available, e-skin will help remotely located clinicians manage chronic diseases and give patients, specifically the elderly, more independence to monitor their health.