AsianScientist (Mar. 14, 2016) – A team of Chinese scientists has developed a device that can generate electricity for medical implants and then dissolve into the body after use. Their work was published in Science Advances.
“Over the last 60 years, implantable electronic systems and devices have undergone a significant transformation, becoming a valuable biomedical tool for monitoring, measuring and soliciting physiological responses in vivo,” co-study lead Dr. Li Zhou from the National Center for Nanoscience and Technology told Asian Scientist Magazine.
“Since in vivo sensing or stimulation is required for a short period of time, degradable implantable electronic devices can provide a solution to overcome inflammation and infections associated with long-term implant utilization. Moreover, subsequent surgical removal of these devices can be avoided which will diminish the pain and cost to the patient.”
The triboelectric generation process is not new, and can be applied to objects on the macro-scale. Triboelectric generation occurs by compressing and releasing materials differing in frictional properties, not unlike how electrodes must differ on a galvanic series in order for a current to result between them.
By experimenting with biodegradable polymers and mimicking biomechanical motion at a frequency of 1 Hz, the team generated an open circuit voltage of up to approximately 40 volts, with a corresponding short-circuit current of 1 µA—sufficient energy to power small implanted devices.
However, for the power source to be used in vivo, other characteristics must also be considered. The generator must not only be able to produce an output voltage, but be biocompatible, to prevent rejection by the host body. It must also be absorbable, so that further surgical procedures to remove the generator would not be necessary.
With these considerations in mind, the researchers implanted their electricity generating devices under the skin of mice to evaluate their biocompatibility. They observed no signs of rejection or infection in the animals, with cleanly healed wounds and no inflammation. Under these conditions, the tribo-nano-generator achieved an output voltage of 3 V for 24 hours, and completely dissolved after 72 hours.
“The most exciting thing is that our results open the possibility of fully degradable electronic devices, for which we provide a potential power source by reclaiming biomechanical energy from the human body,” said Li.
“We can control both the lifetime and the output performance of the biomechanical energy conversion devices through the material design. This would make some in vivo treatment devices more accepted by patients and easier to use, because the whole device can be absorbed in [the patient’s] body and do not need to be removed by additional surgery.”
Other constraints such as voltage output, integration and power management systems that will need to take place between the device and the generator, must be overcome before widespread application of the team’s generator can be implemented. The team is currently working toward addressing them, in hopes that the potential applications can one day become a reality.
The article can be found at: Zheng at al. (2016) Biodegradable Triboelectric Nanogenerator as a Life-time Designed Implantable Power Source.
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