What did you do during the lockdown? Amongst other research tasks, Dr Kim Eccleston took advantage of the peace offered by lockdown to assemble a microwave metamaterial lens from 1900 intricate components. The lens is one of the major elements of a new medical scanner that the Electromagnetics team is developing.
Picture 1: internal view of the microwave metamaterial lens
Picture 2: completed model of the microwave metamaterial lens
Two years ago, Lincoln Agritech was awarded $6m from the Ministry of Business, Innovation and Employment (MBIE) Endeavour Investment fund. The goal of this five-year research programme is to develop a hand-held, non-contact medical scanner that images bone and tissue with sub-millimetre resolution. The Lincoln Agritech Electromagnetics team is leading the programme and is collaborating with researchers from Waikato and Auckland Universities, the Auckland Biomedical Institute, and the University of Nice-Sophia Antipolis (France). The proposed technology will use the unique focusing properties and imaging potential of evanescent waves, which are components of microwaves and can safely penetrate the body, to construct three-dimensional images.
If the research is successful, the microwave-based medical imaging scanner will provide a simple and cost-effective solution, and will be used for point-of-care applications and in medical facilities. The scanner may also be adapted to a wider range of uses in the future, including veterinary scanning and scanning of built structures.
Obtaining clear and sharp images underneath the skin is not easy. Microwaves with a wavelength of around 10 centimetres can penetrate flesh but clear images require a lens to direct electromagnetic waves to a focal point. The size of the focal point gives a measure of the image sharpness. However, the best focus of conventional lenses made from glass or plastic, for example is one wavelength. This means microwave images are insufficiently sharp for medical imaging due to their comparatively large wavelength.
Scientists have known for more than 20 years that a lens made of negative refractive-index materials can focus more sharply than one wavelength. However such materials do not occur naturally, but can be artificially created from arrays of metallic and dielectric objects. These artificial materials are called metamaterials. Scientists and engineers have been challenged to engineer real lenses to the exacting specifications dictated by the theory. The Electromagnetics team has taken up this challenge and has been developing metamaterial lenses using an array of ceramic cubes and metallic strips; experimental results to date show these lenses can successfully focus to less than one wavelength.
The team will continue to further fine-tune the lens to improve its focus and manufacturability over the next few months.