The original headline for the University of Oxford press release was “Batteries for miniature bio-integrated devices and robotics” but it’s not clear to me what they mean by robotics (soft robots? robotic prostheses? something else?).

An October 25, 2024 news item on ScienceDaily announces the research,

University of Oxford researchers have made a significant step towards realising miniature, soft batteries for use in a variety of biomedical applications, including the defibrillation and pacing of heart tissues. The work has been published today [October 25, 2024] in the journal Nature Chemical Engineering.

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An October 28, 2024 University of Oxford press release (also on EurekAlert but published October 25, 2024), which originated the lightly edited news item and posting on EurekAlert, provides more technical detail about this advance, Note: Links have been removed,

The development of tiny smart devices, smaller than a few cubic millimeters, demands equally small power sources. For minimally invasive biomedical devices that interact with biological tissues, these power sources must be fabricated from soft materials. Ideally, these should also have features such as high capacity, biocompatibility and biodegradability, triggerable activation, and the ability to be controlled remotely. To date, there has been no battery that can fulfil these requirements all at once.

To address these requirements, researchers from the University of Oxford’s Department of Chemistry and Department of Pharmacology have developed a miniature, soft lithium-ion battery constructed from biocompatible hydrogel droplets. Surfactant-supported assembly (assembly aided by soap-like molecules), a technique reported by the same group last year in the journal Nature (DOI: 10.1038/s41586-023-06295-y), is used to connect three microscale droplets of 10 nanolitres volume. Different lithium-ion particles contained in each of the two ends then generate the output energy.

‘Our droplet battery is light-activated, rechargeable, and biodegradable after use. To date, it is the smallest hydrogel lithium-ion battery and has a superior energy density’ said Dr Yujia Zhang (Department of Chemistry, University of Oxford), the lead researcher for the study and a starting Assistant Professor at the École Polytechnique Fédérale de Lausanne. ‘We used the droplet battery to power the movement of charged molecules between synthetic cells and to control the beating and defibrillation of mouse hearts. By including magnetic particles to control movement, the battery can also function as a mobile energy carrier.’

Proof-of-concept heart treatments were carried out in the laboratory of Professor Ming Lei (Department of Pharmacology), a senior electrophysiologist in cardiac arrhythmias. He said: ‘Cardiac arrhythmia is a leading cause of death worldwide. Our proof-of-concept application in animal models demonstrates an exciting new avenue of wireless and biodegradable devices for the management of arrhythmias.’

Professor Hagan Bayley (Department of Chemistry), the research group leader for the study, said: ‘The tiny soft lithium-ion battery is the most sophisticated in a series of microscale power packs developed by Dr Zhang and points to a fantastic future for biocompatible electronic devices that can operate under physiological conditions.’

The researchers have filed a patent application through Oxford University Innovation. They envisage that the tiny versatile battery, particularly relevant to small-scale robots for bioapplications, will open up new possibilities in various areas including clinical medicine.

Here’s a link to and a citation for the paper,

A microscale soft lithium-ion battery for tissue stimulation by Yujia Zhang, Tianyi Sun, Xingyun Yang, Linna Zhou, Cheryl M. J. Tan, Ming Lei & Hagan Bayley. Nature Chemical Engineering volume 1, pages 691–701 (2024) DOI: https://doi.org/10.1038/s44286-024-00136-z Published online: 25 October 2024 Issue Date: November 2024

This paper is open access.

Now, I want to highlight a few items from the paper’s introduction, Note: Links have been removed,

The miniaturization of electronic devices is a burgeoning area of research1,2,3. Therefore, the development of tiny batteries to power these devices is of critical importance, and techniques such as three-dimensional (3D) printing4,5,6 and micro-origami assembly7 [emphases mine] are beginning to have an impact. For minimally invasive applications in biomedicine, batteries are also preferred to be soft, biocompatible and biodegradable, with additional functionality and responsiveness, such as triggerable activation and remote-controlled mobility8. However, at present, such a multifunctional microscale soft battery is not available. Although hydrogel-based lithium-ion (Li-ion) batteries demonstrate some of these features9,10,11,12, none currently exhibits microscale fabrication of the battery architecture, in terms of self-assembled integration of hydrogel-based cathode, separator and anode at the submillimeter level. Manual assembly of precrosslinked compartments11 or multistep deposition and crosslinking4 is necessary to avoid the mixing of materials from different compartments at the pregel (liquid) state or during the gelation process. This limitation not only makes it difficult to shrink hydrogel-based functional architectures but also hinders the implementation of high-density energy storage.

Toward that end, Zhang et al. have reported a miniaturized ionic power source by depositing lipid-supported networks of nanoliter hydrogel droplets13. The power source mimics the electrical eel [emphasis mine] by using internal ion gradients to generate ionic current14, and can induce neuronal modulation. However, the ionic power source has several limitations [emphasis mine] that should be addressed. First, the stored salt gradient produces less power than conventional Li-ion batteries, and the device cannot be fully recharged. Second, activation of the power source relies on temperature-triggered gelation and oil for buffer exchange, which is a demanding requirement. Third, the functionality of the power source is limited to the generation of ionic output, leaving the full versatility of synthetic tissues unexploited15,16,17. Last, but not least, while the power source can modulate the activity of neural microtissues, organ-level stimulation necessitates a higher and more stable output performance in physiological environments18.

Here, we present a miniature, soft, rechargeable Li-ion droplet battery (LiDB) made by depositing self-assembling [emphasis mine], nanoliter, lipid-supported, silk hydrogel droplets. The tiny hydrogel compartmentalization produces a superior energy density. The battery is switched on by ultraviolet (UV) light, which crosslinks the hydrogel and breaks the lipid barrier between droplets. The droplets are soft, biocompatible and biodegradable. The LiDBs can power charge molecule translocation between synthetic cells, defibrillate mouse hearts with ventricular arrhythmias and pace heart rhythms. Further, the LiDB can be translocated from one site to another magnetically.

This team has integrated a number of cutting edge (I think you can still call them that) techniques such as 3D printing and origami along with inspiration from electric eels (biomimicry) for using light as a power source. .Finally, there’s self-assembly or, as it’s sometimes known, bottom-up engineering, just like nature.

This work still needs to be tested in human clinical trials but taking that into account: Bravo to the researchers!