Effects of material properties and geometric parameters on electromagnetic-assisted transfer printing

Flexible and stretchable electronics are rapidly evolving to be used in a wide range of applications, including wearable medical devices, implantable health monitoring devices, and bio-integrated systems. As an important method to integrate heterogeneous materials and functional components toward flexible and stretchable electronic systems, transfer printing technology has attracted increasing attention. Among the different approaches in transfer printing, electromagnetic-assisted transfer printing provides a versatile method that allows remote control. In order to investigate the effects of various materials and geometric parameters on the electromagnetic-assisted transfer printing process, a theoretical analysis is combined with the finite element method to investigate the underlying physics. The desirable ranges of parameters (e.g. thickness, radius, and elastic modulus of the upper and lower films in the design) are obtained for the optimized operation. The results indicate that the radii of the upper and lower films should be selected with large values and their upper limits are bound by the size of the functional components to be transferred. Moreover, the radii ratio between the upper to lower film should be within the range of 0.6-0.9. Though small thickness and elastic modulus are preferred in the upper and lower films, the values should be sufficiently large to ensure the strength. Meanwhile, the thickness ratio of upper to lower film should be within the range of 0.5-2. At the same time, the elastic modulus ratio and the height of the lower pickup cavity are shown to have little influence on the maximum displacement of the lower film. With the theoretical predictions validated by the finite element analysis, the results presented in this study are expected to provide useful guidelines for the experimental design.