Mini motors drive custom devices

31 October 2017



Motors and motion control have undeniably furthered the advancement of medical devices in recent years. But fitting these components in ever-shrinking spaces and meeting other demands, such as noise reduction, means designers need to be more flexible than before. Dr Terry Gourlay, head of biomedical engineering at the University of Strathclyde, talks to Ross Davies about the challenges.


As medical devices become increasingly personalised, motors are more crucial than ever. Whether it’s the functionality of the devices themselves or their creation – let’s not forget motors are used in the likes of pick-and-place robots and conveyor belts in manufacturing facilities and labs – motors sit at the core of this particular branch of healthcare.

Certain trends continue to drive their development. In the field of personalised medicine – with its focus on attaining a quicker, more precise diagnosis of a disease – motorised medical devices have a role to play in ensuring the administration of bespoke treatments to patients.

For example, a patient – let’s call him Peter – has a long-standing kidney complaint and receives dialysis. In the past, Peter associated his dialysis treatment with a loud, noisy machine at his nearest hospital, an hour’s drive away. But today, he receives his dialysis in the comfort of his own home. The machine weighs about 30kg – in contrast to machines from ten years ago that were in the range of 90kg – and makes little sound when pushing Peter’s blood. The likelihood is that the thought of dialysis fills Peter with less dread than it did ten years ago. The implementation of a motor in his portable device cannot be overestimated. He no longer needs to venture over to the hospital, for starters.

The move to home care or selfadministered therapies can signify complex medical systems, however. In order to yield real benefit, as opposed to simply mirroring consumer electronics, these therapies also need to have a low enough price tag to satisfy insurance providers, while gaining the confidence of the medical community. This trend towards more personalised medical devices is keeping designers on their toes – not least when it comes to motion control and motor components.

Mini motors

For Dr Terry Gourlay, head of the biomedical engineering department at the University of Strathclyde, the biggest factor of all in motor technology design remains miniaturisation. This has been evident, in particular, in implantable devices – Gourlay’s specific area of expertise. “There has clearly been a lot of growth in the application of micromotor technology in implantable devices,” he says. “Much of the work we are doing now in developing microimplantable pumps is entirely dependent on the ongoing miniaturisation and development of motor systems.

“For instance, we are at a stage now where it is perfectly feasible to implant a motor-driven pump into the vasculature and that is largely due to improvements in the motor technology itself.”

According to Gourlay, the medical device industry hasn’t been solely responsible for developing such motor technology itself; rather, the font of its evolution has been the automotive industry, in which “tiny little motors were built, but with tremendous power; it has changed the face of these particular activities”.

Has this rate of miniaturisation surprised Gourlay, who has been a professor at the University of Strathclyde for over a decade? “Yes,” he affirms. “It’s happened very quickly, and medical devices have miniaturised significantly over the past decade – with an extra surge over the past five years or so.

“I suppose the key to it is recognition that there is an application and an economy around it. There’s a real economy working in the medical-device sector, in terms of the companies involved and the development of these systems. I think that’s well recognised now.

“And that’s just for the motors. Obviously, with the controllers, that’s another issue, but they’ve benefitted from considerable miniaturisation over the past few years.”

Nonetheless, motors and motion control are dependent on application. Miniaturisation might represent a manufacturing cornerstone in today’s market, but it cannot come at the expense of device efficiency. Priorities can vary; sometimes it is simply the shape of the motor to fit the device. For some portable medical devices that feature motors and motion control systems, comfort and ease of use for patients are vital – and not necessarily synonymous with being smaller. With their moving parts, motors are also subject to wear and tear.

From a factory floor perspective, manufacturers also need to keep in mind the multifarious rules that govern the medical device industry before they even begin to think of employing motion or motor control elements.

“We must not forget that the medical device sector is probably the most highly regulated sector on the planet,” says Gourlay. “There’s a lot of guidance in terms of how you fit all your components together – your control and actuator components.

“From an implant perspective, the major engineering challenge is when you put a system into an implant. It’s a no-touch scenario. Again, this boils down to adhering to regulations – you have to be confident that you have a durable technology that is predictable and relatively fault-free. One has to prove that before you can use it on a patient. That’s a very long journey.” But such directives don’t necessarily pose a hindrance, adds Gourlay. When it comes to implantable technologies – “the high end of the field” – following the rules can actually be of great help to engineers. “And there are still tremendous benefits to be had from new-generation motor technologies – especially in other medical sectors,” he says.

He gives pumping technology as an example. “That component movement – through the improvement in precision – is really very small, but really powerful. Motor technologies have enhanced those applications considerably,” he says.

Along with miniaturisation, lower electrical consumption, longer life and lower weight, perhaps the most prized goal in designing an electric motor or medical device system is noise reduction. “It’s something everyone takes into consideration these days,” says Gourlay. “The days of motor-driven platforms pumping out massive amounts of noise in the corner of the lab have largely gone now. And that’s definitely seen as a benefit. Noise was always a reservation for people over the years. But nowadays, these systems are relatively noise-free.”

For implantable devices, another major issue to be considered when it comes to motors is overheating, he adds. “Heat generation is something you really need to consider with implantables and motors,” Gourlay explains. “You need to develop systems that will run cool. You don’t want to put a hot-running system in a patient – nay, you cannot put a hot-running system in a patient in the long run.”

Assembly required

There is no one-size-fits-all solution to the complex demands of the growing universe of medical device manufacturers. Decisions on motors require a bespoke approach. Motor requirements need to be taken into account as early as possible in the design process. This might involve a clear, twoway dialogue between designers and component manufacturers.

This isn’t always a walk in the park. Part of the challenge for motor and motion control players is getting to grips with the complexities of the medical device market, with its wide gamut of potential applications. The list of critical needs for designers today is constantly expanding, whether it is low-maintenance components adapted for battery-operated devices, cost, complexity or fast time to market.

While most devices will perform better if motors meet these requirements, the emphasis designers place on each of these characteristics will vary. But if conducted in the right way, component supplierdesigner partnerships can be mutually fruitful in developing the right technology for the right medical device, says Gourlay.

“We are seeing designers, component suppliers and manufacturers working very closely together,” he says. “In terms of the whole journey of developing a medical device, here at Strathclyde we come up with the devices, but all of those devices tend to be developed hand in hand with component suppliers and motor suppliers.

“That’s because we don’t consider ourselves to be experts on motor and motor control. We are more experts on the application and we work very closely with industry.”

Partnering with component suppliers also allows device designers to benefit from the innovations born out of the highly competitive environment in which suppliers operate. In return, manufacturers are able to keep their finger on the pulse of an equally lucrative and evolving healthcare sector.

“We’ve always found industry to be willing to work in partnership, whether it’s for developing a new stage for a device, or developing motors specifically for implantation,” Gourlay says. “In fact, I’d go as far as to say that industry really likes it. They like to be working at that interface.”

As far as the future of motor control in implantable devices goes, Gourlay foresees miniaturisation continuing to dominate the agenda. “I think there is a clear recognition that smaller is better and we’ve got a defined space into which we implant our devices,” he says.

“For example, if you are going to put a pump into an artery – even a large artery – you have to be sure that it’s easy to place, and it doesn’t interfere with other structures or other organs. We are continuing on that journey now, and seeing a whole plethora of devices that are based around miniature motors. That will only continue.”

Micromotor technology drives implantable pumps that could free patients from being tethered to large medical devices.
Dr Terry Gourlay Dr Terry Gourlay is head of the biomedical engineering department at the University of Strathclyde in Glasgow, Scotland. He has been a professor at the university since 2007. He holds a doctorate from Imperial College, London.


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