An object of the present invention relates to a thermosetting adhesive sheet that, without the use of a metal reinforcement sheet, which is regarded as a major factor responsible for an increase in thickness of electronic devices and other devices, reinforces a flexible printed circuit to such a level that detachment of mounted components, for example, is prevented, prevents warping, and has good electrical conductivity. The present invention relates to a thermosetting adhesive sheet configured to be used to reinforce a flexible printed circuit. The thermosetting adhesive sheet includes a woven fabric, a nonwoven fabric, or a metal base of 50 m or less thickness and a thermosetting adhesive layer adjacent to at least one surface of the woven fabric, the nonwoven fabric, or the metal base of 50 m or less thickness.

Coating inkjet-printed traces of silver nanoparticles (AgNP) ink with a thin layer of eutectic gallium indium (EGaIn) increases the electrical conductivity and significantly improves tolerance to tensile strain. This enhancement is achieved through a room temperature sintering process in which the liquid-phase EGaIn alloy binds the AgNP particles to form a continuous conductive trace. These mechanically robust thin-film circuits are well suited for transfer to highly curved and non-developable 3D surfaces as well as skin and other soft deformable substrates.