Microsystem Technology and Microrobotics

Citation

Andrew, A.M. (1998), "Microsystem Technology and Microrobotics", Kybernetes, Vol. 27 No. 4, pp. 455-457. https://doi.org/10.1108/k.1998.27.4.455.3

Some of the most intriguing applications of robotics come under the heading of microrobotics. Applications in medicine are probably the most interesting of all. Techniques of microsurgery can be facilitated by robotic aids, especially where the surgeon does not have clear access to the operation site. Many possible applications of robotic devices inserted through normal apertures of the body have already been explored with ingenious manipulators attached to fibre‐bundle endoscopes, but much more is possible, some with the help of free‐moving robots.

The medical applications of microtechnology are not limited to surgery, since it can be useful to introduce into the body various sensors, infusers, and stimulators such as heart pacemakers, as well as microscopic items for making single‐fibre connections to nerves.

The use of “radio pills” is mentioned. These are devices that can be swallowed by a subject and can transmit by radio information on such things as acidity, temperature and pressure, while the position of the pill is monitored by X‐rays or ultrasound. Some versions of the pill can be activated by an external signal to take a sample of their surrounding fluid, or to eject a dose of drug.

Microsystem technology has many other applications, for example in the design of sensors used in cars, office machines and even household appliances, where it is advantageous to miniaturise the sensitive elements. In particular, airbags and other safety devices in modern cars depend on small accelerometers.

The first chapter gives a general overview of research initiatives in different countries. The next deals with application areas, with prior but not exclusive attention to medical technology. Although the reader’s interest is stimulated by accounts of possible applications (with even a passing reference to the speculative idea of the inclusion of a swarm of disposable microrobots in a mouthwash, programmed to remove plaque), the main value of the book is its thorough review of means of achieving the results.

The third chapter is on techniques of microsystem technology and introduces various ways of fabricating the items needed. Most depend on deposition of films and their subsequent masking and etching. An impressive variety of methods is brought to bear. Optical and fluidic components receive attention, as do the means of making connections and of encapsulation.

The fourth chapter continues with similar considerations but with special reference to production of micromechanical components. Two main classes of technique are considered. The first is silicon‐based and stems from methods used for microelectronics. Micromechanical components require the silicon to be deposited to a much greater thickness than required for electronics, and etching methods are required to produce clean edges. Some methods depend on the crystalline structure of the substrate and show that the operations are coming close to the single‐molecule level.

The other set of techniques reviewed in this chapter is indicated by the acronym LIGA, or, in German, “Lithographie, Galvanoformung, Abformung”, or “lithography, galvanoforming, moulding”. This has been developed at the Research Centre in Karlsruhe to which the authors belong. It offers the possibility of mass‐production of micromechanical components.

The next two chapters treat, respectively, microactuators and microsensors, and for both of these an impressive range of methods has been tried. The piezoelectric effect is probably the favourite for actuators, but other possibilities include the use of electrostatic and magnetostrictive effects, and of shape metal alloys. Among the types of sensor are some termed biosensors, designed to respond to the concentration level of a particular substance, and even to a specific antibody.

The penultimate chapter is on microsystem technology and information processing, with emphasis of the need to adopt a “systems” view. The components of a microsystem cannot be considered in isolation but must be seen as a whole. The same can be said about any complex system, but the extreme proximity of the parts of a microsystem means that nothing can be shielded from various kinds of mutual interference, including effects of temperature and mechanical deformation, and the systems view is specially relevant. It is argued that reliable operation may depend on adaptive control schemes, and there is a surprisingly comprehensive review of the basis of fuzzy control and of the main types of artificial neural net in support of this, though without any very convincing link to this special field of application.

The final chapter is on microrobotics as such, and some existing devices are described, including micropositioners and micro‐crawlers depending on a combination of a piezoelectric actuator and an anchoring electromagnet. Where the magnetic field is unacceptable, as in the positioning of electron‐microscope samples, a similar effect is obtained by using a pulsed piezoelectric actuator along with inertia and friction. A piezoelectric swimming microrobot is described, with industrial applications in pipelines and possible medical ones in, for example, blood vessels. There is discussion of the use of microrobots for scaled‐down versions of the tasks performed by big robots, namely micromanipulation and microassembly, and a highly versatile “desktop station” with micromanipulator robots is described.

There is an extensive bibliography, and the book is certainly an important contribution which will be an accepted work of reference.