Modulus-Gradient Conductive Core-Shell Structures Formed by Magnetic Self-Assembling and Printing Processes for Highly Stretchable Via Applications

Abstract

In summary, we demonstrated a magnetically self-assembled, modulus-gradient conductive core–shell structure for the stretchable vertical interconnect. Patterned strong magnetic field concentrates the nickel particles toward the center and core–shell structures were formed spontaneously inside the stretchable substrate during the process of substrate solidification. By this way, mechanical robustness of the via was greatly enhanced and it was able to endure large stress by its novel outwardly modulus-gradient structural property. Additionally, since our core–shell structures can be monolithically embedded in situ during formation process of the stretchable substrate, they are compatible with other types of elastomeric substrate materials and there is no requirement of any special strategy such as drilling and filling process, compared to other stretchable via-fabrication process. Furthermore, demonstration of viaembedded LED-array layer laminated on the pressure sensor sheet provided a promising pathway toward layer-by-layer multiple stacking of so-called stretchable printed circuit board for the highly integrated stretchable electronic system applications. Relatively low conductivity in comparison with the conventional vias can be further improved by using nickel composite materials with 1D structure or introducing other ferromagnetic materials with higher electrical conductivity.