Design of the magnetic stamp film for electromagnetic-assisted transfer printing

As a critical step to integrate micro-nano electronic components on the soft substrate, transfer printing allows the facile fabrication of flexible electronics. The key to a successful transfer printing process is to modulate the interfacial adhesion strength at the stamp/device interface. As an advanced approach, electromagnetic-assisted transfer printing explores a sealed chamber with a magnetic stamp film at the bottom that can be reversibly actuated by the externally applied magnetic field. The deflected magnetic stamp film changes the pressure inside the chamber to modulate the interfacial adhesion at the stamp/device interface. Here, we investigate various design considerations and demonstrate a magnetic stamp film with magnetic NdFeB particles dispersed in a silicone polymer. A theoretical model is first established to study the reversible upward (or downward) deformation of the magnetic stamp film in a positive (or negative) magnetic field. The theoretical model reveals the effects of the mass fraction of the magnetic particles, the thickness of the magnetic film, and the magnetic field intensity on the deformation of the film and the transfer printing process. The theoretically predicted linear relationship between the maximum displacement of the magnetic film and the applied magnetic field is validated by finite element analysisand experimental results.