Introductory Course

Medical Applications for Micromachines Part 2
Iwao Fujimasa,Professor,
National Graduate Institute for Policy Studies
carried out with its aim set squarely on the nano world; furthermore, bioindustry has begun creating a huge industrial base for the twenty-first century.
Naturally, medical technologies have also started to directly handle items suchas tissue and cells, and deserving of particular attention is the commencementof studies within the field of genetic medicine focused on intracell injection
methods for substances with dimensions between several microns and severalhundred nanometers. These studies have been started due to the meaningful
medical treatments for a wide range of sicknesses which will be possible if
remote operations can be used to inject a specific DNA probe into a target cell.

From Macro to Micro
From the beginning of the development of micromachine technologies-now
proceeding for over ten years-it has been considered that the field of medicalcare held the potential for the most important, and furthermore, most basic
demands. This time also saw the start of the transfer of practical technologies
from the macro world to the micro world-or in other words, to the submicroscopic world-with the field of medical care being represented in the formof micro surgery. The principal reason for this lay in the fact that medical care
had become focused on treatment; furthermore, this in turn resulted from thedimensional change which occurred in the field of medical care over the pastten-odd years: Specifically, treatment began to move away from classical,
macro applications such as the removal of unneeded organs or, for example, theinjection of medicines over the entire body, and it started to develop in a world
where cells, tissue, or even organs which were less than a centimeter in size oreven smaller became the primary subjects for application. Cells are the primaryelements of life; accordingly, a realization developed that as the subject for
application of medical technologies became smaller and smaller, it would
become possible to conduct medical activities which would be more significant
in terms of human life. In addition, it also became possible for several medical
technologies from the micro world to be put to developmental use.
In the case, for example, of surgical practices-as represented by micro
surgery-over fifty percent of all related fields now involve actions requiring aloupe or microscope; furthermore, micro-forceps and micro-scalpels have now
been applied to use for these tasks. Even in the case of the endoscope
operations which have revolutionized the world of surgery over the last tenyears, these have become characterized by micro-remote operations carriedout via a trocar of less than one centimeter in diameter. Originating frommanual industrial methods, these operations have begun to change in afundamental way through the incorporation of rapidly-developing video-data
technologies and also through the implementation of technologies from theworld of artificial-reality sensing. Already, a large portion of the scalpels,syringes, and micro catheters which are used for the purpose of actual in-bodyoperations in the microscopic realm are provided as one-application,
throwaway devices, and for this reason, the majority of the associatedtechnologies now require mass-production processes which employ industrialtechnologies. It may be said, therefore, that the world of micromachinetechnologies has now for the first time developed a need for industrialoperations.

The Arrival of Nano Quantum Systems
Suitable handling technologies will be required in order that
substances and items of nano-dimensions may be directly operated
on, and the majority of these correspond to micromachinetechnologies. In this world, however, problems lie hidden in thenano region-the region where micromachines now reside. The DNAbase pairs as used by biochips are of several nanometers indimension, and on-chip labs handle material volumes which are lessthan a nanomole (i.e., 10-9) in concentration. As indicated recentlyby many researchers, the reduction of dimensions whichaccompanies the shift toward micromachine technologies has,when considered from the point of view of material units, reached
the realm of several molecules, and further reduction to thequantum level cannot be avoided. The materials which are
subjected to direct operation in the majority of medical-chemistry
examinations have material volumes of the nanomole level. Since asolution containing 631023 molecules per liter is said to have aconcentration of one mole, one cubic millimeter of a one nanomole
solution will contain 63105 molecules. Accordingly, in the world ofnanomole examinations where elements of ten microns in size areused, an examination chamber containing one nanomole of solution
will actually hold a 1/106 fraction of this number-in other words, 0.6
molecules. Micro-TAS (total analysis system) and other similar
technologies recently under development have incorporated thisdynamic, open-system world; accordingly, this indicates entry into
the realm of quantum-wave mechanics, where physical laws
become uncertain with regard to classical and deterministic
theories.
Meanwhile, in the case of micromachining technologies where
the one-micron barrier has already been broken, the size of theexamination elements which this creates has dropped to a levelmeasured in cubic-micron units. In micromachines which havebeen manufactured with dimensions close to one micron, themajority of macro-world rules will not be applicable with respect toinduction of the chemical reactions which handle the substances
contained. Analysis in the micromole range has recently become
the most commonly-applied, and with the exception of those cases
which handle protein structures and other substances of a certain
degree of size, it may be said that for this type of analysis also, asolution must be found for the electronic-related uncertainty
problems in systems which perform analysis using commonlyapplied electrochemical electronic reactions. If nanomoles are to
become the subject of operations, this world will expand to include
technology where today's regularly-produced micromachines havesides of one-hundred microns, and it is quite possible that newtechnologies will be required for examination and materialidentification purposes. In other words, if the world of microelectromechanical systems were to coincide with the world oforganisms containing aqueous solutions, this would lead to the startof the creation of, not a micro world, but a nano world;
furthermore, it should be emphasized that biomedical
micromachines have already entered the realm of the nanomachine, and that further reduction to the level of nano-quantum
systems is an inevitability.

From Micro to Nano
Occurring almost simultaneous with the start of transition from macro to
micro for those items subjected to medical-treatment practices, the subjects ofexaminations also began to switch from microscopic cells and metabolites of acertain density towards cell-internal organelles, genes, and minute volumes of
immune-system substances; similarly, such examinations have also begun todeal with items and substances which are more important with regard to life
control. Since the dimensions of cell-internal substances now correspond to
the nano level, and because it is now necessary to handle extremely low
densities measured in nanomoles, it may be said that a shift from micro tonano is beginning to occur for examination items. We cannot allow ourselves
to ignore the passage over the past ten-odd years-as characterized by thehuman genome project and the like-of the science of biomedicine into therealm of the nanometer.
Although the development of biomedical examination elements anddevices has been overlooked during the course of previous micromachine
projects, it may be taken for granted that bio-elements, chips, and the like will
be incorporated into the next generation of micromachine and nanomachinetechnologies. Furthermore, the last few years have seen rapid development
both in the field of industrially-manufactured DNA chips, protein
immunochips, and the like, and also in the field of micro-inspection elements
as typified by on-chip labs which are put to bed-side use as liquid inspection
chips; these developments, too, may be considered as a natural matter ofcourse. As indicated by the announcement of the DNA chip in 1997, thedevelopment of post-genome technologies in the field of biomedicine is being

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