Biodegradable Self-Powered Electronics
Authors: Li Zhou 
Published: February 2020

Electronics used for transient implantable medical devices have some specific requirements that are more restrictive than for other applications, such as high reliability, controllable lifetime, biocompatibility or biodegradability [1]. However, the internal heat, capacity loss, and battery failure are the common problems of traditional power sources for the electronics. Meanwhile, the it requires second surgery to remove the devices after the accomplishment of their work cycles. In this context, electronic systems entirely built with biodegradable materials and self-powered sources are of growing interest for their potential applications in systems that can be integrated with living tissue and used for diagnostic and/or therapeutic purposes during certain physiological processes. TENGs and PENGs have superior performance in converting biomechanical energy and could convert electrical energy in cardiac pacemaker, health monitoring, cell or tissue engineering. Therefore, several works have been done studying degradable self-powered electronics for biomedical engineering in our group [2-4].
In 2016, Zheng et al. reported the first biodegradable triboelectric nanogenerator (BD-TENG) for short-term in vivo biomechanical energy conversion. Enabled by the design of a multilayer structure that is composed of biodegradable polymers (BDPs) and resorbable metals, the BD-TENG can be degraded and resorbed in an animal body after completing its work cycle without any adverse long-term effects. It is demonstrated the potential of BD-TENG as a power source for transient implantable medical devices. When applying BD-TENG to power two complementary micrograting electrodes, a DC-pulsed electric field (EF) was generated (1 Hz, 10 V/mm), and the nerve cell growth was successfully orientated, which was crucial for neural repair.
Soon afterwards, Jiang et al. developed a fully bioabsorbable BN-TENGs in vivo using natural materials. It provided a new design idea for TENG and other energy harvesters using natural materials. The operation time of BN-TENG in vivo and in vitro could be modulated from days to weeks by modification of silk fiber encapsulation film. Using the proposed BN-TENG as a voltage source, the beating rates of dysfunctional cardiomyocyte clusters are accelerated, and the consistency of cell contraction is improved. This provides a new and valid solution to treat some heart diseases such as bradycardia and arrhythmia.
Immediately after that, we fabricated a serial of biodegradable (BD) iTENGs and effectively tuned their degradation process in vivo by employing Au nanorods (AuNRs), which responded to the near-infrared (NIR) light sensitively. The degradation of our BD-iTENG could be triggered and come into effect very quickly with rational manipulation. Moreover, the output voltage could be applied on fibroblast cells and significantly accelerate cell migration across the scratch, which was very beneficial to wound healing process.
In summary, we have fabricated biodegradable self-powered electronics which could harvest biomechanical energy and convert electrical energy into biomedical engineering, such as cardiac pacemaker, health monitoring and cell or tissue engineering.

References

[1] J. A. Rogers. JAMA, 2015, 313, 561–562.
[2] Q. Zheng et al. Sci. Adv., 2016, 2, e1501478
[3] W. Jiang, H. Li, Z. Liu et al. Adv. Mater., 2018, 1801895
[4] Z. Li, H. Q. Feng et al. Nano Energy, 2018, 54, 390-399.