Geometry and mesh size control the EMI shielding in 3D printed conducting shape memory PU structures

Innovations in the telecommunication industry and its growth in the direction of wireless technologies have effectuated electromagnetic interference (EMI) as their ramification. The progressive miniaturization of gadgets has made circuitry complex bringing several circuit elements in the vicinity of each other, allowing them to interfere with each other. EMI shields are used to prevent such cross-talk and interferences. To design intricate parts in systems, 3D printing is gaining much popularity. With increased emphasis on both reliability and multi-functionality especially in the defence industry, the so-called 'smart' structures and 'intelligent' materials that can reduce the complexity of the system are also gaining importance. Keeping these requirements in mind, herein, we have developed EMI shields using silver coated 3D printed shape memory polyurethane-based structures using a simple mussel-inspired electroless plating method. To gain further insights, the effect of geometry (hexagonal, square and pyramid) and mesh size/pyramid height (varying between 1 mm to 5 mm) on shielding effectiveness was also studied in this work. The prepared samples showed excellent shielding properties with values reaching as high as -46 dB. The SE values were found to decrease with increasing mesh size for hexagonal and square shaped meshes, and the converse was observed for pyramidal structures. Moreover, the shape memory properties of polyurethanes were retained to a large extent after dopamine coating and electroless deposition - opening avenues of applications not only as EMI shields but also in the field of shape memory triggered actuators and sensors.