Arbitrarily Shape-Manipulation of High Stiffness Electronic Composite through Shifting Neutral Surface of the Material

Transformation a sensor of 2D type into 3D structure can realize a differentiated function. A sensor for 3D structure must be consisted of a thin or low-stiffness material to avoid a failure of sensor’s electrode. However, when the sensor was transformed the 3D structure, it requires additional tools to maintain the 3D structure, because the structural stiffness is not sufficient. In this study, we produced an electronic composite that can be flexibly bent and transformed into an arbitrary 3D shape and maintain the transformed shape due to sufficient structural stiffness after deformation using the principle of moving the neutral surface of Shape Memory Polymer (SMP). This sensor is a multi-layer composite in which SMP embeds a high sensitivity crack-based sensor. The SMP has low stiffness (2.2 MPa) at high temperature (60 °C), so the electrode is not broken during transformation, and has high stiffness (1200 MPa) at low temperature (25 °C), so it may maintain a 3D shape even after transformation. For this reason, the composite initially made in 2D form can be transformed into three 3D structures. Each structure is activated to detect external stimuli that are not detected in the initial form; Large strain (2 to 35%), Small pressure (1 to 30 kPa), Small bending (1 to 15 °). In addition, even after transforming to all 3D shapes and returning to the initial shape, there was also a reversibility in which the resistance didn’t change at all. Based on these results, we demonstrate that high stiffness electronic composites that can transform into arbitrary 3D shapes and maintain the transformed shape.