Materials for stretchable electronics

Yu Zheng is a Ph.D candidate in the Chemistry department at Stanford University under the supervision of Prof. Zhenan Bao. She received a B.S. in Chemistry from Nankai University in 2017. Her current research focuses on developing multifunctional polymer semiconductor materials for high-performance stretchable electronics.

Next-generation wearable electronics require enhanced mechanical robustness and device complexity. Besides previously reported softness and stretchability, desired merits for practical use include elasticity, solvent resistance, facile patternability and high charge carrier mobility. Here, we show a molecular design concept that simultaneously achieves all these targeted properties in both polymeric semiconductors and dielectrics, without compromising electrical performance. This is enabled by covalently-embedded in-situ rubber matrix (iRUM) formation through good mixing of iRUM precursors with polymer electronic materials, and finely-controlled composite film morphology built on azide crosslinking chemistry which leverages different reactivities with C–H and C=C bonds. The high covalent crosslinking density results in both superior elasticity and solvent resistance. When applied in stretchable transistors, the iRUM-semiconductor film retained its mobility after stretching to 100% strain and exhibited record-high mobility retention of 1 cm² V⁻¹ s⁻¹ after 1000 stretching-releasing cycles at 50% strain. The cycling life was stably extended to 5000 cycles, five times longer than all reported semiconductors. Furthermore, we fabricated elastic transistors via consecutively photo-patterning of the dielectric and semiconducting layers, demonstrating the potential of solution-processed multilayer device manufacturing. The iRUM represents a molecule-level design approach towards robust skin-inspired electronics.

 

Takatoshi Abe is a Technology Research Manager with Panasonic North America in California. He graduated with Masters in Materials Science and Engineering from the Tokyo Institute of Technology

Takatoshi has been with Panasonic for 14 years. His experience includes product development and manufacturing technology roles for a variety of electronic material technologies including circuit board laminates, electrically conductive materials, and optical materials for which he holds numerous technical patents. Takatoshi began his career in R&D and now is working in technology scouting, marketing, and business planning.

Conventional electronic assembly processes like SMT reflow require high-temperature resistant materials. However, conventional pliable and stretchable polymer films like thermoplastic polyurethane (TPU), normally used for printed and flexible hybrid electronics, exhibit poor temperature–resistance creating challenges in the printing and curing of functional materials like conductive pastes, surface mount assembly, as well as end-use durability.

The technology development center of Panasonic Electronics Materials in Osaka, Japan has been developing materials for FHE/PE applications specifically to address these challenges. Through experiments and use-case devices, we have demonstrated that these new stretchable materials have the durability and heat resistance to be compatible with traditional SMT assembly processes. This presentation will explain the substrate technology in detail and introduce some use-case demonstration parts made using these materials.