A new miniature battery could power tiny devices integrated into human tissues, paving the way for such instruments to be used in a range of applications in biology and medicine, British researchers reported last night.
Researchers at the University of Oxford, UK, say their work is a significant step towards realising miniature bio-integrated devices that can directly stimulate cells and could have important therapeutic applications, such as delivering targeted drug therapies and accelerating wound healing
However, up to now there has been no efficient way of providing power at the microscale level.
Writing in Nature, researchers from the university’s Department of Chemistry say they have developed a miniature power source that alters the activity of cultured human nerve cells, inspired by how electric eels generate electricity.
The miniaturised soft power source is produced by depositing a chain of five nanolitre-sized droplets of a conductive hydrogel, each of which has a different composition, enabling the creation of a salt concentration across the chain.
The droplets are separated from their neighbours by lipid bilayers, which provide mechanical support while preventing ions from flowing between the droplets.
The power source is switched on by cooling the structure to 4°C and changing the surrounding medium. This disrupts the lipid bilayers and causes the droplets to form a continuous hydrogel, thereby allowing the ions to move through the conductive hydrogel, from the high-salt droplets at the two ends to the low-salt droplet in the middle.
The energy released from the ion gradients is transformed into electricity, which allows the hydrogel structure to act as a power source for external components.
The study, led by Dr Yujia Zhang, found the activated droplet power source produced a current that continued for more than 30 minutes. The maximum output power of a unit made of 50 nanolitre droplets was about 65 nanowatts (nW). The devices produced a similar amount of current after being stored for 36 hours.
Dr Zhang said: “The miniaturised soft power source represents a breakthrough in bio-integrated devices. By harnessing ion gradients, we have developed a miniature, biocompatible system for regulating cells and tissues on the microscale, which opens up a wide range of potential applications in biology and medicine.”
The team says the device’s modular design would allow the combination of multiple to increase the voltage and/or current generated.
This, they add, could help to introduce next-generation wearable devices, bio-hybrid interfaces, implants, synthetic tissues, and microrobots.
Professor Hagan Bayley, the research group leader for the study, said: “This work addresses the important question of how stimulation produced by soft, biocompatible devices can be coupled with living cells. The potential impact on devices including bio-hybrid interfaces, implants, and microrobots is substantial.”
A Microscale Soft Ionic Power Source Modulates Neuronal Network Activity Nature 30 August 2023; doi: 10.1038/s41586-023-06295.
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