Ab initio simulations of the degradation of biodegradable batteries

Deacon, Benjamin and Murphy, Samuel and Hardy, John (2021) Ab initio simulations of the degradation of biodegradable batteries. Masters thesis, Lancaster University.

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Abstract

Transient implantable medical bionics (TIMBs), such as biodegradable batteries that disappear after their operation are gaining attention. They potentially facilitate the deployment of novel instructive biomaterials for regenerative medicine. Implantable, biodegradable and biocompatible batteries may be capable of satisfying the power requirements of some biomedical devices before harmlessly degrading. One material of particular interest for the construction of biodegradable batteries is Bombyx Mori silk. Lancaster University is developing a biodegradable battery that will utilise silk both in the electrolyte and to encase the battery. Using the silk offers the battery a degree of protection that enables the device to operate for several days before it harmlessly degrades. Key to tuning the lifetime of the battery is understanding how the structure of the silk changes under different operating conditions and how this changes the diffusivity of the cations (i.e. Mg2+) and other species such as choline nitrate used as the ionic liquid in the electrolyte. This project will aim to further this understanding through the use of quantum mechanical methods. This project quantifies the behaviour of various molecules in the presence of SF, including water, choline and Mg ions. This helps to see how the biocompatible and biodegradable batteries will behave when made from SF. This is completed via DFT simulation as to perform the experiment is unfeasible. For example, the diffusion pathway of water can not be experimentally generated. Furthermore this project has generated ramachandran plots via DFT for silk fibroin which have not been carried out on this material previously. This allows for a detailed comparison with classical mechanical data. This understanding will allow for further work to elucidate and exploit the properties of SF. Further understanding will allow for fine-tuning of how long the SF biodegradable battery will take to break down; this can be changed for the required use. This will help to understand the ions contribution to the effect on the decay rate of the electrode.