Stretchability, Conformability, and Low-Cost Manufacture of Epidermal Sensors

Epidermal sensors and electronics represent a class of artificial devices whose thickness, mass density, and mechanical stiffness are well-matched with human epidermis. They can be applied as temporary transfer tattoos on the surface of any part of human body for physiological measurements, electrical or thermal stimulation, as well as wireless communications. Except for comfort and wearability, epidermal sensors can offer unprecedented signal quality even under severe skin deformation. This chapter tries to address two fundamental mechanics challenges for epidermal sensors: first, how to predict and improve the stretchability and compliance when epidermal devices are made out of intrinsically brittle and rigid inorganic electronic materials; and second, when laminating on human skin, how to predict and improve the conformability between epidermal devices and the microscopically rough skin surfaces. Since the ideal use of epidermal devices would be one-time, disposable patches, a low cost, high throughput manufacture process called the “cut-and-paste” method is introduced at the end of this chapter.