Introductory Course

Medical Applications for Micromachines, Part 4
Iwao Fujimasa,Professor,
National Graduate Institute for Policy Studies
Micro-Electrodes: Data Interface with Living
Organisms

Micro Fluid Devices: an Essential MicromachineTechnology for Medical Measurements

Mechanical industries tend to view electronic systems as
borrowed systems. With the human body, however, we must
consider contact points between an electronic system andnerves in the human information system as a complex systemfrom the beginning. The development of an interface between
neural circuits and external instruments is essential as a basetechnology for micromachines. Recently Japan has beenpresented with a golden opportunity to make up lost ground inpacemaker development.
Forty years have passed since development began on
pacemakers, now the most widely used artificial organ. The
pacemaker is also a good example of the increased use of
micromachines, achieving complex control and highcompatibility with the human body. Pacemakers that have until
recently been developed to treat bradycardia are starting to beincorporated as implanted defibrillators for treating tachycardia.
We are just now developing other methods of applying
micromachines to the nervous system. In addition, diseases
brought about by the nervous system of the heart and diseases
brought about by nerves in the cerebral/peripheral nervous
system have many common points in the form of electric
signals. A great number of regions controlling human bodyfunctions can be manipulated electrically, and engineers haveshown an interest in this field. However, we have tried toprovide interface with macro-instruments located external tothe body to provide a less invasive operating method. As aresult experiments in Japan using the approach of installing amicro-electrode into the body have unfortunately been limited
to animal experiments in our engineering departments.
Although many approaches in a clinical setting have been
proposed, there has been little research aimed at making thispractical. Nowadays, researchers of neural systems have begun
to assert that the 21 st century is not only the age of gene
research, but also of brain research.
Studies on micro-electrodes implanted in the human body
have increasingly been conducted in the areas of visual andauditory systems, wherein multichannel needle electrodes areimplanted to directly stimulate sensory areas in the brain.
Some clinical achievements have been observed in the auditory
field. A strong potential has also been seen in approaches tostimulate afferent nerves between sensory organs and the brain
and in direct stimulation of sensory cells. In the auditory field,
cochlear implants have found practical uses, while in the visual
field there have been repeated experiments conducted tostimulate optic nerves using electrode, with inclined needle
array. Japan has also been recognized for its advanced medical
technology on implanting multichannel microsensors in thecranium to sample signals from the brain and determinefunctional regions. Many clinical examples that have beenconducted are now common in health insurance coverage.
Many approaches have been developed for treating
peripheral nerves, such as microsleeve electrodes and nerve
growth electrodes that incorporate the fiber-growing region of
the nerve stump in an electrode. Studies are being conducted
to create an interface between nerves and artificial devices,
both internal and external to the body. Studies on both of thesemicro-electrodes and electronic devices must cover such
medical engineering issues as the compatibility ofmicromachining methods and materials with the body tissue,
and the intervention of nerve growth factors, such as endocrine
substances. We must create new areas of research.

It is well known that the object of medicine, the human
body, comprises 70% water. Many medical instruments operateusing an aqueous solution or a solution containing cells ormicro-particles. It is a well-known historical fact that the firstidea for creating an automated biochemical analyzer, called anauto analyzer, came during the development of tabletopchemical plants. With these devices, methods of pumping,cleaning devices, separating samples, and detecting reactions
were studied at dimensions near the micro-level to enable a
drastic size-reduction in the plants.
Although there have been various proposals for developing
micro-fluid devices since the beginning of micromachinedevelopment, even today these devices only function as a singlecomponent. We must reinvestigate and reconstruct all systemcomponents with the aim of versatility. To do this, we must
begin by acquiring base technologies for designing micro-fluidsystems, including theories for analyzing fluid behavior at highviscosity and approaching particle transport and the need forrheological analysis, which knowledge can help us zero in on
the essence of living matter. It would not be an exaggeration to
say that developing technical elements as systems will influence
tomorrow's sample testing apparatus. However, we must stilldevelop numerous components and study them as
microsystems in order for micro-instruments used in sample
measurement, such as micro-TAS (total analysis system) andon-chip labs, to become the next-generation of auto analyzers
useful in medical treatment.

New Medical Industries Created from an On-site
Demand for Micro-Instruments
In order to popularize medical products and their use in thehome, we must develop technologies for manufacturing cheaperand smaller products. By taking up each instrument one by one,
perhaps we will see the need to explore the feasibility andsignificance of manufacturing them at a micro-size. Most
conventional medical equipment is manufactured manually one
product at a time, resulting in high prices that have stifled themarket. Manufacturing this equipment at micro-sizes would giverise to industrialization and lower costs, which could generate alarge demand. Blood sugar testing apparatus that are alreadyused in the home have generated a new direction for diabetes
control and have generated an enormous market. Micro-syringes
for use in the home, which have helped reform conventional
methods of administering medicine, and the much smaller
catheter, have the potential to radically change medical treatmentin the future. Obviously in either case it will be necessary todevelop impartial ideas with much consideration for the clinicalsites. It is clear from experience that the more widespread themicromachine system can be used, the more likely the system may
become Japan's original industry. The objective of our efforts ismost likely to develop common equipment of widespread use
aimed primarily at treating lifestyle-related diseases.
Since the components of micromachine systems are small,
we have a tendency to think it difficult to mount circuits for
information systems therein. However, the smaller the devices
become and the more widely they are used, the moreindispensable it is to automate data processing in devices andelements. If our research does not include the study ofsomewhat fixed distributed data processing systems in
micromachines and their integration as systems, there willprobably be less possibility of micromachines becoming anessential technology in the medical industry.

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