META

Artefacts made from biomaterials (e.g. medical implants, scaffolds for tissue engineering, drug administration) are composites of variable density and structure. However, the majority of present manufacturing methods produce components of homogeneous structure and material. Furthermore, these manufacturing methods are oriented towards mass production and are seldom economically suited for the production of customised parts.

Project: Generation of Heterogeneous Cellular Structures by Sonication

Description:

It has long been recognised that the engineering performance of materials can be dramatically improved if their composition and structure is varied to precisely match the conditions surrounding it. Such heterogeneous materials have engineered gradients of composition or structure which offers superior performance over traditional homogeneous materials. Indeed frequently heterogeneous materials demonstrate dramatic synergy with the overall performance of components being far greater than a straight forward mix of the individual constituents. They include composite materials, functionally graded materials (FGM) and heterogeneous materials with periodic microstructure. These types of materials offer great promise in fields where a high performance technology is required (e.g. biomaterials, aerospace). However, the literature survey identified a need for digitally controllable manufacturing technologies for heterogeneous materials.

If the feasibility of ultrasonically tailoring of the cellular structure of polymers can be established, it will open a range of applications, the first most likely ones being in the area of biomedically functional materials. It is hoped that this project will lay the foundations for future projects where specific biomedical functionalities can be explored, centred on the control of agent release, filtration, cell colonisation and local density control. Each of these functionalities has a range of potential applications in artificial organs, drug release and tissue engineering.

Scope:

The technologies required to enable a viable exploitation of biomaterials are:

• CAD - able of representing both internal and external shape (i.e. geometry, material properties) and structure (i.e. framework) and capable of generating instructions for digital manufacturing systems.
• Digital manufacturing - able to selectively form precise shapes and structures with an order of accuracy measurable in microns.
• Materials - suitable for additive manufacture, i.e. extrusion, deposition, sol-gel, sintered, adhesive binding, etc.
• Environmental - sustainable, renewable, and biodegradable.

Among the many biomaterials available are natural (e.g. Lignin) and synthetic (e.g. polyethylene) polymers. Polymers consist of small repeating units, or isomers, strung together in long chains. The flexible structure of polymers has enabled this group of materials to be useful in applications from plastic garbage bags to rubber tires and foundry works. In many materials, processing conditions can induce the polymer chains to link with each other along the length of the chain to produce a wide variety of mechanical properties. This is known as cross-linking. Cross-linking can increase the density of materials to improve their strength and hardness; however, cross-linked materials often lose their flexibility and become brittle.

The research objective is to perform a feasibility study towards digital manufacturing methods (e.g. rapid prototyping) using sustainable resources such as natural fibres and polymers. A study of polymer cross-linking parameters is also necessary to meet the requirements of current biomedical applications.