Douglas C. Engelbart

Stanford Research Institute

Menlo Park, California

More and more electronics people are becoming aware of the exciting possibilities inherent in some of the mircominiaturization or molecular-engineering approaches to new-device development, and more and more device-oriented people are turning their attention to this area. For many years our device work has involved size scales which have generally not varied significantly for a given type of component or element. Experimental models could usually be built to the same size scale as was planned for the final development model, and there was seldom any occasion for the component researcher to consider the effects which a change in size scale might have upon the phenomena which his devices utilize.

As a matter of fact, the relationships between physical phenomena which the component researcher is used to depending upon will change, and much of his valuable intuition and judgement gained by work on "normal-sized" components will not be applicable, when he begins working with radically different size scales. The purpose of this paper is to call to attention to the long-established art of similitude, and show how it can help us bridge the gap between our past experience and our new problems. The paper will bring out no great sweeping discoveries, nor will it attempt to be particularly tutorial regarding the art and practice of similitude. Rather it is intended to deliver a message to those people who are trying to get oriented in the device possibilities which may arise from new microminiature materials-handling techniques. The message is that they should look to the art of similitude for help in orienting themselves, in evaluating new-device possibilities, or for conducting research on new devices. This message will be explicitly stated several times, and the body of



the paper will be aimed at showing how similitude can provide this help.

Application of similitude can yield a transformation schedule for changing all of the common electronic parameters, corresponding to a given change in the length parameters, to yield a scale model of a given electronic device which can be expected to perform in a manner exactly similar to that of the original model. Using this transformation to map the prospective microminiature design up to "normal" size can allow us immediately to apply our intuition and judgement to an analysis and evaluation of the design. Discussion of this general procedure will be included, and some examples will be given for a few typical types of devices, e.g. magnetic, parametric, and cryogenic. There are general practical implications to be deduced from application of this transformation technique, and there are also some other types of transformation which may be useful for work in the microminiature electronics area. These will be mentioned in conclusion, along with an emphasis upon the purpose of the paper: to point out that the well-developed art of similitude can, for apparently the first time, be a very real help to the electronic-device researcher.