Hybrid Printed Rigidity-Programmable Substrate/Liquid Metal 3D Circuits Toward Stretchable Electronics

Stretchable electronics have the unique capability of 3D (three dimensional) deformation, overcoming the brittleness of traditional inorganic electronics. However, during large deformations, different scale strains between the rigid and stretchable components lead to mismatch, causing interconnect failures. Therefore, the development of the rigidity-programmable substrate with effective strain shielding capabilities has become a research hotspot. Furthermore, the exponential growth in electronic density presents challenges in the circuit design of stretchable electronics. The urgent need is to develop highly integrated stretchable electronic systems. In this study, a highly integrated stretchable pulse sensor with effective strain shielding capabilities using hybrid 3D printing technology is developed, which comprises electronic chips, a rigidity-programmable substrate/encapsulation layer printed by using PSC (polydimethylsiloxane/silica-nanoparticles composite)-based ink, and LM (liquid metal)-based 3D circuits. First, the PSC-based ink is optimized to enhance the strain shielding effectiveness of the rigidity-programmable substrate. Meanwhile, 3D printing parameters are optimized to achieve high printing precision with minimum line widths below 100 µm. The resulting stretchable pulse sensor demonstrated good mechanical and electrical stability under complex 3D deformations, including bending, twisting, and stretching. The PSC region strain of the sensor is only ≈2% when the global strain is up to ≈65%, which exhibited effective strain shielding capabilities.