Pre-strain buckling for stretchability

A widely used route to stretchable conductors is to bond a stiff thin film onto a pre-stretched elastomer and then release the pre-strain. The compression buckles the film into a periodic wavy or out-of-plane wrinkled pattern; subsequent stretching simply flattens the waves, so the film accommodates large system-level strain while the conductor itself experiences only small local bending strain. This is the mechanical principle underlying both wavy-ribbon interconnects and many island-bridge layouts.

Design levers are the amount of pre-strain (which sets the achievable stretch), the film thickness and modulus contrast (which set wavelength and amplitude), and adhesion (bonded versus free-standing bridges). The approach is well characterised by thin-film mechanics, but out-of-plane buckling adds height that complicates conformal contact and thin-film encapsulation.