MMBOP: Multiphysics Modelling of BiOdegradable Polymers

The proposed research aims to develop new physics-based modelling and simulation tools to understand and predict the mechanical response of biodegradable polymers. Such materials can gradually break down into harmless constituents and eventually disappear after having fulfilled their structural function. In healthcare applications, materials biodegradability is a desirable feature, because it enables the fabrication of temporary implantable devices that do not require removal surgery, such as cardiovascular stents, sutures, or orthopaedic fixation devices. In recent years, biodegradable polymers have also attracted enormous attention due to their potential to replace traditional inert plastics in an attempt to address the plastic pollution problem. Biodegradable polymers are also attractive to reduce reliance on oil, since many biodegradable polymers are naturally sourced.

From an engineering design perspective, biodegradable polymers introduce new challenges due to seemingly contradictory requirements: they need to degrade relatively fast after they have completed their intended function, but they must also maintain suitable mechanical performance while in use. This contrasts with traditional design engineering strategies, where one usually wants to delay the onset of degradation as much as possible. In the absence of reliable engineering design guidelines, current practice essentially relies on trial and error, which is particularly time-consuming and costly given the relatively long timescales for degradation (of the order of months or years). There is thus a need for reliable modelling and simulation tools to complement experimental research and development. Physics-based models are also needed to elucidate the complex interplay between mechanics and chemistry in load-bearing biodegradable devices.

This project will deliver a continuum modelling platform as well as constitutive models to describe concurrent deformation and chemical degradation in biodegradable polymers. The project focuses on hydrolytic degradation (i.e. the breaking of polymer chains under the attack of water), which is the primary degradation pathway in biomedical polymers. The model will account for water-induced swelling, progressive damage by chain scission, and mass loss by release of the degradation products. The models will be implemented into robust computational tools to simulate the degradation of devices of arbitrary shape under complex loading conditions. The project will generate new knowledge on the role of various factors impacting the mechanical performance and lifetime of biodegradable polymers. Ultimately, this project will equip academic and industrial beneficiaries with rational design tools to boost productivity in research and development, and improve reliability and performance of biodegradable devices.