MEMS in medicine: these sense-mimicking chips may herald a new age of bionics.

Ed.: For the full article, please see circuitsassembly.com/cms/content/view/1820/

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MEMS, or microelectromechanical systems, are tiny chips that can be produced by semiconductor processes to combine mechanical sensing, control and motion to solid-state electronics to deliver extraordinary functionality and versatility. Essentially all the mechanical and electromechanical machines from the macro-world can now be crafted into a tiny chip that can enter the micro-world and interact with life systems. MEMS can sense pressure, detect motion, measure forces, identify bio-agents, pump and control fluids, and perform other actions that have great value to the medical and biological fields. BioMEMS is the term used to describe the chips designed specifically for these applications. These BioMEMS chips can serve as chemical and biological analysers, micro-pumps and controllers, hearing aid components and many more applications. In the future, BioMEMS "medical practitioners" could become permanent inhabitants of the body.

MEMS is the ultimate enabling technology for the integration of almost any physical, chemical and biological phenomena that include motion, light, sound, chemistry, biochemistry, radio waves and computation, but all on a single chip. These chips can mimic our senses, and thus eventually be used as body replacements or enhancements heralding a new age of bionics. While simpler systems, such as hearing aids, have been implemented, extraordinary bio-systems will emerge in the future. MEMS will add vision, hearing, tactile feel and other sensory input while the on-chip electronic logic function will serve as the "brain" to condition signals, organize data and control, analyze and integrate input and output. The merging of motion, sensing and computation represents a significant new level in technology.

MEMS devices can possess high-level integration for numerous functions. This unification of functionality encompasses high precision micro-mechanical motion, optics, micro-fluidics, living cell interaction, sound, radio waves and much more. Senses could even be enhanced, making it possible to see in the dark or extend the hearing range. The additional features of computation and centralized control of all actions into a fully integrated system could deliver surprisingly versatile new products. MEMS is also about technology convergence where miniature devices-including gears, propellers, turbines, pumps, mirrors, motors, radio elements, radiation sensors and many types of detectors and other assemblages - are syner-gistically united in a new micro- and even nano-world. MEMS can combine and integrate complete systems, from a library of parts that includes micron-sized motors, tweezers, pumps, separators, injectors, needles and scalpels. MEMS places systems together on a fully integrated and self-contained single piece of silicon, or other construction material, that previously could only exist in the macroworld. These previously isolated technologies are now converging onto a tiny single chip of silicon.

BioMEMS devices, however, will become the most important class in the future. They can already detect specific ions and molecules, sense pressure within an artery and even help detect defective DNA. MEMS adds the eyes, nose, ears and some senses that humans don't even possess, but merges mechanics with the electronic brain of semiconductor logic on a single chip. MEMS can also exert control using untiring electrically-powered "muscles" to move, manipulate or pump fluids and dispense drugs. The merging of motion, sensing and computation represents the most advanced level in a technology that is still embryonic. While much of traditional commodity electronics is leaving America's shores, the advanced biomedical field remains in good health and growing.

Who are some of the players? Integrated Sensing Systems Inc., or ISSYS, performed studies on its own BioMEMS wireless, batteryless, implantable pressure sensor as described by Nader Najafi, Ph.D., president and CEO. Animal studies showed the accuracy and proved the functional feasibility of BioMEMS technology for biological sensing. The results were very encouraging and exceeded the requirements, including high sampling speed and resolution. A second generation of wireless sensors is being developed to provide a total system solution. ISSYS is developing intelligent BioMEMS sensors and systems to enhance the quality of medical treatment that can apply to:

* Measure pressure gradients across heart valves to help assess valve disease.

* Diagnose and monitor congestive heart failure.

* Measure cardiac output and compliance.

* Monitor intracranial pressures in hydrocephalus patients.

* Understand glaucoma disease progression and improve patient care.

* Improve gastrointestinal tract diagnostic capabilities to help treat gastro esophageal reflux disease (GERD).

* Assist in diagnosis of urological disorders.

* Measure drug delivery rate for infusion systems.

ST Microelectronics is also active in BioMEMS. Its prototype lab-on-a-chip is very compact, making it suitable for point-of-care applications. ST has produced MEMS for autos and industry for many years, but this product is its first venture into BioMEMS. It has invested in state-of-the-art research facilities to build up the BioMEMS product lines rather than use retired fabs, as some others have done. Its silicon lab-on-a-chip will become economical through large volume production using the company's massive semiconductor fabs. This gives BioMEMS products the production benefits usually only found in the huge clean-rooms of semiconductor manufacturing of standard electronics. Instead of the small volumes produced by workshop-style startup companies, the high-volume capacity of ST can bring the niche BioMEMS market into one of high-volume productivity, lower costs and constant market pressure on prices.

The Future

Robotic surgery and augmentation is on the horizon. Microchips will be placed inside the body, such as on heart tissue for repair or inside of blood vessels, for monitoring. The chips could contain cells that can generate specific types of tissue, such as muscles, organs, blood and others. Chips could also contain chemicals that would stimulate the growth of blood vessels, or medication that is slowly released into the body at specific points and under particular demands. BioMEMS will move heart disease treatment to the next level and has the potential to let physicians assess the benefits of their work in the operating room instead of waiting for symptoms. A surgeon could also place a slow-release anesthetic in the wound at the end of the surgical procedure, eliminating traditional post-operation pain relief. A painkiller released slowly inside the body would prevent the pain impulses from reaching the brain so a patient would never feel the pain.

Preventive medicine will also be enhanced to enable us to diagnose the earliest abnormalities and plan more suitable and successful strategies. BioMEMS chips equipped with sensors could detect mutated genes or dangerous levels of hormones, and enable doctors to determine which tissues to treat long before the situation goes critical. The day may come when MEMS-enabled micro-robots, or even nanobots, travel through the body to clear arteries and make repairs, borrowing a scene from the classic 1966 sci-fi movie Fantastic Voyage. MEMS has already delivered tweezers, scalpels, injectors, cell-splitters, all kinds of sensors and several kinds of propulsion devices, including turbines. Indeed, in the future, your doctor may advise to take two MEMS and get some rest.

Ken Gilleo, Ph.D.

Ken Gilleo, Ph.D., is with ET-Trends LLC (et-trends.com); [e-mail].