Miniaturisation is a relatively new concept, but it’s one that has been gaining steam over the past two decades of medical device engineering. Across the industry, however, many are still coming to grips with how to be successful in this area.
There is not one singular challenge to it, because problems and goals tend to be specific to each device and application. Yet many specialists within the medical device field agree that they’re worth grappling with, as miniaturisation can come with vast benefits for all involved.
For end users, it can mean being able to utilise medical devices more easily and accessibly from home, as they are smaller, lighter and less obtrusive. Meanwhile, manufacturing costs are likely to be lower due to the use of batch fabrication processes and reduced amounts of raw materials. From an environmental standpoint, smaller devices typically generate less waste throughout the life cycle. Manufacturers should think long and hard about whether making devices smaller and flexible is worth it – in terms of labour, sustainability and cost. Though if they decide it is, it’s a choice that can pay dividends.
Setting up for success
It sounds obvious, but making smart design decisions early – including choosing the right components – can save a lot of stress down the line. Dr Adrian Horrell, head of electronic systems at Team Consulting, says: “Current chip and passive component fabrication and packaging technologies coupled with advanced printed circuit board manufacture and assembly can let you squeeze a lot of functionality and performance into tiny volumes – but this brings formidable design challenges.
“Besides the fundamental ‘3D jigsaw puzzle’ of fitting everything into place, issues will arise in areas like signal integrity, thermal management and wireless performance. Having the right simulation and modelling tools will also help.”
Device-makers should consider all these factors up front when developing designs. And when devices still aren’t small enough, Horrell recommends considering advanced design and manufacturing processes from the chip industry such as system-in-package assembly or creation of an application-specific integrated circuit as ways to further reduce the size of electronic components. However, the upfront cost of these can be very high.
Collaboration can make a big difference here, too. Whether between hardware and software engineers, or electronic and mechanical or industrial designers, communicating ideas is key for device-makers to overcome challenges posed by miniaturisation requests. According to Horrell, having the right computer-aided design (CAD) and simulation tools can support this process.
“There is a large role for EME [electronics and medical engineering] departments to work collaboratively with manufacturers in the design to shape the next generation of medical devices,” adds Ben Caldicott, head of medical engineering at Healthcare Partners. He recommends that manufacturers communicate with people who service the devices, study feedback on trends and failures, and apply these insights to make physical improvements. That includes dealing with limitations, including those potentially introduced by the Waste from Electrical and Electronic Equipment Directive (WEEE) – new EU rules for how electrical waste should be dealt with. This means that manufacturers “aren’t going to be able to do a great deal with some of the polymers they use in these plastics”, says Caldicott.
Scaling smart
Alex Casson, professor of biomedical engineering at the University of Manchester, deems the route to scale-up the main challenge for making electronic devices smaller and more flexible. That means that manufacturers should plan for this from the get-go.
Casson points out that many flexible or stretchable electronic devices are made as one-offs in the laboratory. Yet the design rules for larger-scale manufacturing often differ greatly to those for one-off or prototype devices.
“As a rule of thumb, devices made in a clean room with silicon processing-based technologies are the very thin flexible ones,” he explains. “Whereas printed electronics-based devices tend to be thicker or less flexible, but with potentially easier routes to scale-up, such as via roll-to-roll printing.”
Dr Conor O’Mahony, principal researcher at the Tyndall National Institute, agrees that roll-to-roll processing can be a good idea – and it’s better for the planet, too. “Circuit boards are environmentally unfriendly to manufacture, associated with significant amounts of waste chemicals and metals. So, the industry needs to move towards flexible manufactory procedures, like roll-to-roll processing, where everything is built on a flexible film.”
Here, Horrell adds, it can be beneficial to engage with component and manufacturing suppliers as early as possible, so you can access their latest component offerings – and their expertise. “There’s little point designing a device that can’t be manufactured effectively and economically… Before committing to costs, consider your performance and size targets carefully. Don’t get trapped into spending millions of pounds and years of effort to shave off the last half a millimetre unless it’s really necessary.”
Power-efficient design
For Horrell, the most obvious reason for miniaturising implantable or wearable devices is their need to fit on the body without interfering with users’ daily life. With larger devices, potential challenges may concern portability and squeezing them into already crowded environments, such as intensive care units or ambulances, where space is limited alongside critical equipment. Plus, he points out: miniaturisation usually means not much room for batteries, so power-efficient design becomes even more critical.
“With careful system design, engineers can eliminate unnecessary functionality and provide hardware power-saving features – these might include the means to power down subsystems when not in use, or dynamically changing processor clock speeds to match workload. There is also capacity for alternative power delivery methods such as energy harvesting or wireless power transfer,” says Horrell.
He adds: “Software has a huge impact on system power demand, meaning efficient, power-aware implementation is vital – software and hardware development need to be very closely coupled to achieve this.”
There are other practical concerns here, too. For instance: consider the challenge of bonding rigid components to a flexible substrate. “It’s tricky to get electronic chips to bond reliably to flexible substrates,” says O’Mahony. “There’s less room for error as the substrate is bending and you get stresses at the junction between the flexible and rigid parts.”
How can this be overcome? O’Mahony explains: “Emerging fabrication technologies will use printing techniques to deposit integrated circuits on flexible organic substrates. In contrast to conventional, rigid silicon devices, these polymer-based chips are inherently bendable and/or stretchable, reducing the stresses at bond junctions where the chips are interfaced to the substrate.”
Sustainable solutions
Sustainability is something many experts agree is a pressing concern, particularly where medical devices are single-use. Caldicott appreciates the benefits of these devices for both patients and facilities – for instance, Crohn’s patients often take biologic infusions at home – but also recognises the disadvantages from a reusability perspective. While these devices are often plastic, electrical resources are also commonly used and then disposed of, leading Caldicott to consider their carbon footprint “a major challenge”.
Caldicott’s firm mainly operates within acute settings. “Devices used within this clinical setting are reusable and getting smaller, but the electronics and medical engineering team can still provide full-life managed services for them. There are more discrete components, which should actually lower costs maintenance-wise.”
Similarly, O’Mahony has sustainability on the mind – and thinks others should, too. Based at a centre with an interest in wound care, he gives the example of embedding thin, flexible electronics into dressings to monitor wound conditions: “The problem here is it’s disposable, hazardous biowaste that must go straight in an incinerator. Many of the batteries are also hazardous waste, so can’t even be incinerated. How do we dispose of a hazard we can’t incinerate?”
According to O’Mahony, the difficulties in disposing of single-use devices is a widespread concern among device companies. “Using them is a brand decision – but a dangerous one,” he warns. “It’s why not many of these products are on the market… for companies, the choice is: ‘Do we deploy this technology, or wait for a sustainably better output, and better materials and facilities with organic materials that require less waste?’”
Don’t forget the end user
But Caldicott’s main piece of advice for manufacturers is to engage more with end users, asking how they can future-proof their devices. “We’re getting there for some devices but still have one foot in the past,” he says.
He gives an example: in his workplace, the Royal Surrey County Hospital, clinicians are still physically writing out data. However, in the coming years he expects that there will be a gradual move to storing and sharing data electronically. Consultants are likely to shift to viewing scans, analysing trends from vital signs monitors and even setting up infusion devices remotely.
Miniaturisation certainly poses challenges for manufacturers, but it’s a trend that is set to shape the future of the field. Through smart planning and collaboration, the design and manufacturing processes can be made smoother.
