Wearable technology, wearables, fashion technology, smartwear, tech togs, streetwear tech, skin electronics or fashion electronics are smart electronic devices (electronic device with micro-controllers) that are worn close to and/or on the surface of the skin, where they detect, analyze, and transmit information concerning e.g. body signals such as vital signs, and/or ambient data and which allow in some cases immediate biofeedback to the wearer
Wearable technology has a wide range of applications, which is growing as the area matures. With the popularity of the wristwatch and activity tracker, it has become a key feature in consumer electronics. The Apple Watch is a popular smartwatch on the market. Wearable technology is being used in navigation systems, sophisticated fabrics, and healthcare, in addition to commercial applications. Wearable technology must be validated for its dependability and security qualities before it can be used in critical applications.
Epidermal electronics is an emerging field of wearable technology, termed for their properties and behaviors comparable to those of the epidermis, or outermost layer of the skin.These wearables are mounted directly onto the skin to continuously monitor physiological and metabolic processes, both dermal and subdermal. Wireless capability is typically achieved through battery, Bluetooth or NFC, making these devices convenient and portable as a type of wearable technology. Currently, epidermal electronics are being developed in the fields of fitness and medical monitoring.
Current usage of epidermal technology is limited by existing fabrication processes. Its current application relies on various sophisticated fabrication techniques such as by lithography or by directly printing on a carrier substrate before attaching directly to the body. Research into printing epidermal electronics directly on the skin is currently available as a sole study source.
The significance of epidermal electronics involves their mechanical properties, which resemble those of skin. The skin can be modeled as bilayer, composed of an epidermis having Young’s Modulus (E) of 2-80 kPa and thickness of 0.3–3 mm and a dermis having E of 140-600 kPa and thickness of 0.05-1.5 mm. Together this bilayer responds plastically to tensile strains ≥ 30%, below which the skin’s surface stretches and wrinkles without deforming. Properties of epidermal electronics mirror those of skin to allow them to perform in this same way. Like skin, epidermal electronics are ultrathin (h < 100 μm), low-modulus (E ~ 70 kPa), and lightweight (<10 mg/cm2), enabling them to conform to the skin without applying strain. Conformal contact and proper adhesion enable the device to bend and stretch without delaminating, deforming or failing, thereby eliminating the challenges with conventional, bulky wearables, including measurement artifacts, hysteresis, and motion-induced irritation to the skin. With this inherent ability to take the shape of skin, epidermal electronics can accurately acquire data without altering the natural motion or behavior of skin. The thin, soft, flexible design of epidermal electronics resembles that of temporary tattoos laminated on the skin. Essentially, these devices are “mechanically invisible” to the wearer.
Epidermal electronics devices may adhere to the skin via van der Waals forces or elastomeric substrates. With only van der Waals forces, an epidermal device has the same thermal mass per unit area (150 mJ cm−2 K−1) as skin, when the skin’s thickness is <500 nm. Along with van der Waals forces, the low values of E and thickness are effective in maximizing adhesion because they prevent deformation-induced detachment due to tension or compression. Introducing an elastomeric substrate can improve adhesion but will raise the thermal mass per unit area slightly. Several materials have been studied to produce these skin-like properties, including photolithography patterned serpentine gold nanofilm and patterned doping of silicon nanomembranes.[