PHPMA/PEI blend film healing process. The crossed black lines are cracks made with a blade. (Source: Advanced Functional Materials, Vol. 25, Issue 24, pgs. 3745-3755)
Printable and flexible electronics carry many advantages, from their low cost to their potential use in wearable and implantable sensors. Incorporating self-healing properties into these electronics is highly desirable due to their “soft” nature, which makes them susceptible to scratching, rupture, and other damage, all of which can cause a loss of functionality. Now, Johns Hopkins engineers have developed the first self-healing, printable, flexible, and low-voltage organic field effect transistor (OFET) structure.
“There are two options for self-healing in materials. One option is that in the event of a break or rupture a chemical kit will also break and repair the material. The other option, which is the direction we went, is that the material itself has in it some capability to repair itself without a kit. The bonding that holds this material together is somewhat reversible,” said Dr. Howard Katz, professor of materials science and engineering and the corresponding author on the paper.
The researchers used a versatile polymer blend system as a dielectric layer. The polymer blend demonstrated a high thin film capacitance, pronounced electrical and mechanical self-healing behavior, and promise in improving the sensitivity of a gas sensor, particularly for ammonia. The team published their findings in the June 24 issue of Advanced Functional Materials.
Weiguo Huang, a former postdoctoral scholar in Dr. Katz’s research lab and first author on the paper, suggested the idea for the research.
“Weiguo had been working on an insulating part of a sensor for another project and tested this material. He showed me the results and said this would be an interesting area to explore,” said Katz.
Other authors on this paper include Kalpana Besar, Gregory Wiedman, Yu Liu, Wenmin Guo, and Prof. Kalina Hristova (JHU Materials Science); Yong Zhang and Prof. Kevin Hemker (JHU Mechanical Engineering); Shyuan Yang and Ionnis J. Kymissis (Columbia University, Dept. of Electrical Engineering); and Jian Song (State Key Laboratory on Integrated Optoelectronics, Jilin University).
This research was supported by primary funding from the Flextech Alliance. Additional support was provided by the Johns Hopkins Institute for Clinical and Translational Research. The dielectric property study was supported by the National Science Foundation.