Materials
the use of a limb or to regulate toilet functions. You could potentially heal the peripheral nervous system.” Currently, Hardy is looking at the specific set of signals in the brain that lead to epileptic fits, with a view to creating an implanted device that could respond in real time to suppress them. Other potential uses of SMPs with imprinted circuits include drug delivery systems with electronic control systems. For instance, a sensor system that detects analytes in bodily fluids associated with certain disease states could trigger the delivery of medication to alleviate symptoms.
A broad horizon for innovation As more and more potential applications for SMPs emerge, there will be increased focus on the development of new materials. In the development of biodegradable SMPs, for example, new polymer classes, developing responsiveness to new stimuli, and thorough characterisation of materials properties and performance in vivo will play key roles in shaping the development of new medical devices. A wide variety of polymers exist, including many that are biodegradable, but what lies ahead is a thorough examination of their shape memory properties. For all polymers, whether biodegradable or not, more investigation on biocompatibility and toxicity will be as essential as investigating the response to different triggers.
“Designing systems that are responsive to multiple stimuli opens up applications that might have been impossible in the past,” says Hardy. He adds that for now, many of the practical examples are seen in other industries, using the building and construction as an example. Here, he says, SMPs have been used to create adapting insulating foam that expands and fixes itself, which could even have implications for the use of foam technology in marine salvage operations to transport material out of sunken vessels like the Titanic. Part of the reason we haven’t seen developments as fast in the medical device industry has to do with concerns about patient safety. “In principle, when there are no ethical concerns, the market opens up faster,” says Hardy. “One challenge with electronic interfaces in the body is that they are made with metals or alloys, which causes an inflammatory response. Patient safety concerns are the reason the bar for market entry is set so high by regulators, and along with finding the best materials for SMP applications, Hardy says working on ways to make them more bioavailable will be the key to getting them into the clinic. “We want something to be usable in surgery but soft enough to be accepted by the body, so engineering and medical acceptance are the two prongs of research,” he concludes. ●
Composite Metal Wire for Medical Devices
Combine two or more metals or alloys into a clad metal wire "system"
that acts as one.
Medical Device Developments /
www.nsmedicaldevices.com 103
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