Chinese scientists have developed a biodegradable wireless device that can receive and even store energy inside a person – under their skin. It could power bioelectronic implants, such as fully biodegradable drug delivery systems.
Wireless power supply and energy storage device developed by Chinese scientists. Image source: Lanzhou University
Implantable bioelectronic systems such as monitoring sensors and drug delivery implants are minimally invasive and reliable ways to accurately monitor and treat patients. However, the development of power modules to power these devices is lagging behind the development of biocompatible and biodegradable sensors and circuit blocks, according to a paper led by researchers at Lanzhou University published Thursday in the journal Science Advances.
Although biodegradable power supplies exist, they can often only be used once and are not powerful enough for biomedical applications. In addition, power supplies connected to transdermal chargers can cause inflammation, and power supplies that run on non-rechargeable batteries may require surgical replacement, which can lead to complications.
To address this deficiency, the researchers proposed a wireless implantable power system that has “both high energy storage efficiency and favorable tissue interaction properties.” Its soft and flexible design allows it to conform to the shape of tissues and organs.
The wireless power delivery device consists of a magnesium coil that charges the device when an external transmitter coil is placed on the skin over the implant. Just like wirelessly charging a smartphone. The energy absorbed by the coil under the skin goes through a circuit and then enters an energy storage module consisting of hybrid zinc-ion supercapacitors (ionistors). In terms of their properties, ionistors occupy an intermediate position between a capacitor and a chemical power source, such as a battery. Although supercapacitors store less energy per unit volume than lithium batteries, they have a high power density and can therefore consistently deliver large amounts of energy.
The prototype power system, embedded in a flexible, biodegradable chip-like implant, combines energy reception and storage in one device. The energy can be supplied via a circuit directly to the connected bioelectronic device and the supercapacitor and stored there.to provide a constant and stable discharge to power a bioelectronic device» after the loading process is complete.
Zinc and magnesium are vital to the human body, and the researchers note that the amounts contained in the device are below the daily intake, making the dissolvable implants biocompatible. The entire device is surrounded by a polymer and wax that can bend and deform according to the structure of the material in which it is embedded. placed.
Tests of the device on rats showed that it can work effectively for up to 10 days and completely dissolve within two months. The operating time of the device can be changed by changing the thickness and chemical composition of the encapsulation layer. To demonstrate the functionality of the power source, the researchers connected stacked supercapacitors to a receiver coil and a biodegradable drug delivery device and implanted them into rats. The implantable prototype was not enclosed in a single device, but rather consisted of separate, encapsulated parts connected together. Rats with yeast fever were implanted with a drug delivery device containing an anti-inflammatory drug. During the 12-hour observation period, the temperature in the group without an implant was significantly higher than in the group with an implant.
The researchers found that the problem of the device turning on and off persists because it only stops working when the charge is used up. However, in their opinion, the duration of switching on and off can also be controlled through controlled charging initiation. According to the researchers, the rats that received the implant without charging also experienced some passive drug release, as the temperature measured in this group was also reduced compared to the control group.
However, the article states that the prototype “represents an important step forward in the advancement of a wide range of implantable transient bioelectronic devices that can provide efficient and reliable energy solutions“
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