MEMS: Think Big, Work Small

15 July 2010 (Last Updated July 15th, 2010 18:30)

Micro-electrical-mechanical systems could open up a new vein of medical devices. Shekhar Bhansali, University of South Florida, reveals to Nic Paton how MEMS have the potential to change the face of healthcare.

MEMS: Think Big, Work Small

Medical devices that are 80,000 times smaller than the thickness of human hair sound like something in the realm of science fiction.

But, according to the University of South Florida's Dr Shekhar Bhansali, the development of micro-electrical-mechanical systems (MEMS) and the use of nanotechnology are not only realities right now, but also have the potential to radically change how medical devices are manufactured and used in the future.

MEMS combine silicon-based microelectronics with micro-machining technology, making it possible to develop complete systems on a tiny chip. Devices generally range from a millimetre down to 20 micrometres. 

"A lot of MEMS medical devices have been developed, and they are much more sensitive and robust than their conventional counterparts," says Bhansali.

Medical applications

"MEMS have the potential to radically change how medical devices are manufactured and used in the future."

Biomedical MEMS devices are used in vivo, so can be used to regulate substances such as insulin; if levels fall below a set point, a 'smart' pill can release some of it into the body.

MEMS are also useful for precision surgery, biotelemetry, drug delivery and, in particular, biosensors, which can be used as long-term sensors in prosthetics, and critical sensors during operations or in home testing.

The latter is an area in which Bhansali believes medical device manufacturers are likely to see significant changes as MEMS move into the mainstream.

"You will have mini sensors or electrodes that will enable people to carry out tests in their own homes," he says. "It could lead to someone being able to test for the so-called stress hormone cortisol, which is synthesised from cholesterol and so can be picked up in saliva or urine." 

MEMS technology also has applications for drug delivery. It can, for example, enable hundreds of hollow microneedles to be fabricated onto a patch. This patch is then applied to the skin and the drug delivered to the body by micropumps. And because the microneedles are not big enough to reach and stimulate nerve endings, they cause no pain.

"There will be advances in microneedles and chemically derived patches," says Bhansali. "One area being looked at is how to increase the permeability of needles [to make drug delivery more effective], which in time might be something that impinges on the needles business. We are probably looking at a five to ten-year time frame, but it is something that could happen."

Bansali argues that another key area for development is gastroenterology, including capsule endoscopies where a patient swallows a pill that is fitted with a camera or wireless transmitter. "Then we will also increasingly find MEMS being used within invasive procedures such as colonoscopies or gastric reflux."

Lab on a pill

Such a 'lab on a pill' normally incorporates a digital camera, light source, battery and radio transmitter, with the MEMS element being its sensors. These devices have the advantage of requiring no sedation and showing a view of the entire small intestine, aiding the diagnosis and early detection of diseases such as colon cancer.

"MEMS enable hundreds of hollow microneedles to be fabricated onto a patch."

The sensors within the pill sample body fluids, temperature, dissolved oxygen levels and pH. They will normally collect data over a 12-hour period, after which they are excreted. The data will be transmitted wirelessly to a card attached to the patient's arm.

There is also potential for MEMS devices to make surgical procedures less invasive, Bhansali suggests. Within the microsurgery arena, for example, there are MEMS-driven scalpels that use a piezoelectric motor to help accurately position the scalpel.

They may also include MEMS pressure sensors to measure the force exerted on the area being operated, and it is possible to incorporate microchannels to flush out fluid and debris while cutting.

MEMS technology also has the potential to help with skin resurfacing and, although not yet commercially available, Bhansali says it is possible to incorporate MEMS structures onto rotary elements to aid the removal of skin lesions.

Investment considerations

Cost, inevitably, is a key area of debate when it comes to MEMS. While the R&D and pioneering science behind this area is not exactly cheap, this investment has to be weighed against the longer-term savings MEMS devices could bring.

"Obviously one can compare the cost of a conventional needle, which is just a few cents, with a microneedle, which may be, say, $10, you're going to develop an argument," Bhansali says. "But you also need to recognise that if by investing in these areas and by moving to higher cost technologies you end up with lower care or after-surgery costs – because people are in hospital for less time – that is also going to be a persuasive advantage. Yes, the test may cost more, but you will be taking dollars out of the rest of the delivery chain, so it is very much a trade-off."

Surgical systems tend to be one of the highest costs within healthcare. So a fundamental challenge for medical device manufacturers will be how to adjust to this as and when MEMS starts to move more into the mainstream.

For hospitals, too, the challenge will be around adopting a brand new technology that is perhaps not going to become commonplace for three to five years.

"Surgical systems tend to be one of the highest costs within healthcare."

"There will be a major challenge in terms of the healthcare delivery models, with more decentralisation and personalisation of medicine," says Bhansali. "There will be challenges around smarter ways of working, and the sponsoring and adoption of new technologies.

"The costs of these technologies will have to come down, as that is still a barrier for the moment. But when they do I can really see them moving into surgical procedures and investigations."