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3D printing of micro-scale graded shape memory components for in-vivo actuated medical devices


Project Description

Micro-actuators and micro-robots have great potential for evaluation and treatment of medical conditions. Such devices require highly controlled actuation at a micro-scale to provide controlled motion, testing of tissue compliance, biopsy, etc, and this is a prospect offered by functionally-graded shape memory alloys (SMAs), where the shape memory effect is locally tailored within the device. The aim of this project is to adapt an established laser-based manufacturing process for the fabrication of such functionally-graded SMAs, with functional grading at a micro-scale.

Devices and components manufactured from functionally graded SMAs can provide actuation in response to external stimulation (stress or temperature variation), outperforming conventional actuation mechanisms such as electromagnets or electrical motors in terms of work output density. Such performance is ideal for the micro-devices for use in minimally invasive medical applications such as precise incision, tissue identification, tactile sensing for disease and tweezing.

This PhD project will be focused on demonstrating the feasibility of a laser-based manufacturing process for mm-scale SMA components that are functionally graded at a scale of 10’s of microns. This concept requires 3D control – at the micro-scale – of both material composition and thermal treatment. By depositing the functionally graded SMA material onto substrates with appropriate material properties (e.g. carbon fibre substrates), additional tailoring of the overall mechanical performance of the device will be achieved. The project will exploit the high degree of control (both spatial and temporal) that is possible with laser-driven processes. Specifically, the approach will be to combine the high precision laser LIFT (Laser Induced Forward Transfer) process – that can build components from sub-micron layers of different materials – with highly localised thermal tailoring of SMA material parameters. Our concept is to deposit pure metals onto a multi-track ‘donor ribbon’ (rather like a multi-coloured typewriter ribbon) for the LIFT process that allows “voxels” (of typical dimensions a few microns across and hundreds of nm high) of different metals, e.g. Ti, Ni and Cu to be sequentially deposited onto a target substrate and build up micro 3D structures voxel-by-voxel, with 3D spatially varying voxellated composition. Post-treatment of the deposited array would then allow control of interdiffusion between the voxels and thermal treatment of the alloy providing very tight control of the composition and thermal treatments far beyond that available with conventional LIFT, direct vapour deposition or powder consolidation processes.

The ideal candidate will have a background in either photonics and lasers, or metallurgy. They must be flexible and willing to learn new skills and knowledge in this multi-disciplinary project.

Funding Notes

The project is funded by the National Manufacturing Institute for Scotland and Renishaw plc. Project specific equipment and materials etc. is provided via an associated EPSRC project. A full stipend of £15,000 per annum (tax free) is payable. A top-up to the stipend may be available for an exceptional UK or EU candidate.

How good is research at Heriot-Watt University in Physics?

FTE Category A staff submitted: 20.80

Research output data provided by the Research Excellence Framework (REF)

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