The development of implantable bioelectronic devices provides potential solutions for health monitoring and diagnosis and treatment of diseases. However, breakthroughs in power modules have lagged far behind the sensor nodes and circuit units integrated with tissues. In a recent study, researchers developed a soft implantable power system incorporating wireless energy transmission and storage modules.
Overcoming Problems in Bioelectronics
In bioelectronics, experts apply electrical engineering principles to biology, medicine, and even human behavior. Since this field is still emerging, it faces challenges like power sources. Even if biodegradable batteries are available, bioelectronic devices do not last long enough and discharge power in an unstable way.
As a result, temporary implants either need to be tethered to a power source or put up with poor batteries, which is not an ideal solution. Meanwhile, permanently implanted ones tend to be rigid, more prominent and do not flex with the body. Because of this, a small, bendy, wirelessly chargeable, and reliable source is preferred.
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Potential of Implantable Supercapacitor
Scientists from Lanzhou and Dalian Universities in China and Penn State in the U.S. have created a gadget powered by a supercapacitor. It contains a molybdenum sulfide (MoS2) cathode, an alginate gel for an electrolyte, and a zinc foil anode. This component is enough to power a drug-delivery device for about ten days before being broken down and absorbed harmlessly by the body.
The power-storing implant was designed to inductively charge using a magnesium coil to flex and move with the body. Its components, including a supercapacitor, a charging coil, a control board, and a drug-delivery module, are all built on a poly-L-lactic acid substrate, which is both flexible and biodegradable.
Powered by a rechargeable supercapacitor, the device is implanted in a patient's body, releasing medication over time. At the end of treatment, the package, including the crude electronic circuit, is dissolved completely and harmlessly.
Supercapacitors work like a typical capacitor, storing energy in the electrical field between plates and a battery alternative. These supercapacitors cannot hold as much charge as a battery, but they are small, sufficiently stable, and cool to go inside a human body.
Systematic investigations were conducted by the research team to understand the charge storage mechanism of the supercapacitor and to evaluate the biodegradability and biocompatibility of the materials. The researchers tested their design on laboratory rats who suffer from yeast-induced fever. The implants were configured to release the non-steroidal anti-inflammatory drug ibuprofen. One group got a charged implant, the other received an implant without charging the supercapacitor, and a third one served as a control group.
It was found that the wirelessly transmitted energy not only provides power directly to applications but can also charge supercapacitors to ensure a constant, reliable power output. The power supply capabilities of the device have also been successfully demonstrated for controlled drug delivery—once inside the human body, the implants function for roughly ten days. After two months of being implanted, the device showed a complete dissolution.
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