Mechanics of nonbuckling interconnects with prestrain for stretchable electronics

The performance of the flexibility and stretchability of flexible electronics depends on the mechanical structure design,for which a great progress has been made in past years.The use of prestrain in the substrate,causing the compression of the transferred interconnects,can provide high elastic stretchability.Recently,the nonbuckling interconnects have been designed,where thick bar replaces thin ribbon layout to yield scissor-like in-plane deformation instead of in-or out-of-plane buckling modes.The nonbuckling interconnect design achieves significantly enhanced stretchability.However,combined use of prestrain and nonbuckling interconnects has not been explored.This paper aims to study the mechanical behavior of nonbuckling interconnects bonded to the prestrained substrate analytically and numerically.It is found that larger prestrain,longer straight segment,and smaller arc radius yield smaller strain in the interconnects.On the other hand,larger prestrain can also cause larger strain in the interconnects after releasing the prestrain.Therefore,the optimization of the prestrain needs to be found to achieve favorable stretchability.

Systematic study on the mechanical and electric behaviors of the nonbuckling interconnect design of stretchable electronics

Recently, we developed a nonbuckling interconnect design that provides an effective approach to simultaneously achieving high elastic stretchability, easiness for encapsulation, and high electric performance for stretchable electronics. This paper aims to systematically study its mechanical and electric behaviors, including comparisons of the nonbuckling and buckling interconnect designs on stretchability, effects of the thickness on electric performance, and modeling and experimental investigations on the finite deformation mechanics. It is found that the results on stretchability depend on the layouts. Long straight segments and small arc radii for nonbuckling interconnects yield an enhancement of stretchability, which is much better than that of buckling designs. On the other hand, shorter straight segments or thicker interconnects are better to lower the resistances of interconnects.Therefore, optimization of the designs needs to balance the requirements of both the mechanical and electric performances. The finite deformation of interconnects during stretching is analyzed. The established analytic model is well validated by both the finite element modeling and experimental investigations. This work is key for providing the design guidelines for nonbucklingbased stretchable electronics.