EDUCATION Microelectrical Mechanical Systems in Surgery and Medicine Arnold D Salzberg, MD, Matthew B Bloom, MD, Nicolas J Mourlas, PhD, Thomas M Krummel, MD, FACS It is apparent that in the year 2001, the methods by which one negotiates the world are becoming more effi- cient and more powerful. This phenomenon is encoun- tered when checking email or reviewing the latest jour- nal articles on a desktop computer. The trend in microcomputing is evident in surgery, which is certainly at the forefront of miniaturization technology. To take advantage of next generation tools, physicians must first be aware of the current trends in technology, and then understand them well. The need for such an under- standing serves as the impetus for this discussion of mi- croelectromechanical systems (MEMSs). MEMS comprise a technology that most use without realizing it. A car with an airbag restraint system, for example, is likely to use a micromechanical system in the form of an accelerometer, which deploys a life-saving airbag (Fig. 1). Other common examples include the nozzle in an inkjet printer, the fuel injection system in a car, and the sensor in a vehicle’s antitheft system. Surgeons, internists, and researchers have always tried to interact directly with the physical domain of the dis- eases that are fought every day. Surgeons have long used loupes to reapproximate tissues on the microscopic level. Oncology, transplant surgery, and cardiology researchers have tried to approach diseases microscopically. MEMS technology allows us to do this. Most MEMS devices are less than the size of a 50-m human hair and can be used singly or in vast groups of millions. Such miniaturization might seem at the outset to be advantageous in all cir- cumstances, but this is not universally true. Some of these devices can be outsized and overpowered by the organic and physiologic processes they encounter, re- ducing their effectiveness. Because a microscopic dimen- sion is not always efficient, intense planning for the scal- ing of these devices is imperative. As the medical community continues to rely on com- puters to enhance treatment, physicians require an in- strument that does not only function to compute, but one that also performs actual tasks. MEMS fill this need. MEMS involve integrated circuits, which can actuate, sense, and modify the outside world, on the micrometer scale. One must begin by reviewing the theory of microme- chanical devices. These devices are made largely of sili- con, the same material used in producing the central processor of a personal computer. They perform on the micron level, having sizes of approximately 10 to hun- dreds of micrometers. Some are smaller than the width of a human hair. MEMS are generated using a unique fabrication method called micromachining. Each mi- cromachined device will have a particular capability that will interact with the world on the macro scale. Specifi- cally, there are three main advantages to MEMS: size, reliability, and inexpensive production cost. All MEMS fabrication methods share particular common features, which will be discussed in the following sections. There are advantages and disadvantages that are in- herent to MEMS technology. To understand these points, it will be useful to have at least a cursory under- standing of the MEMS “toolbox.” 1 This article provides insight into the toolbox by dissecting the fabrication process involved in the manufacture of integrated cir- cuits, and will touch on many of the aspects that are involved in the fabrication of micromechanical devices in a manner intended to be useful to the nonengineer physician. The goal is to outfit the reader with a mean- ingful understanding of the basic science behind each of the real-world applications discussed in Section II of the article. In Section III, there are descriptions of a number of important, existing medical applications of MEMS technology, with a succinct discussion of the advantages and disadvantages of each. Section IV reviews some dis- advantages of the technology as an overall field, and No competing interests declared. Received May 4, 2001; Revised September 26, 2001; Accepted October 3, 2001. From the Department of Surgery, Stanford University (Salzberg, Bloom, Krummel) and The Center for Advanced Technology in Surgery at Stanford, Stanford Department of Electrical Engineering (Mourlas), Stanford, CA. Correspondence address: Thomas M Krummel, MD, FACS, 701B Welch Rd, Suite 225, Stanford, CA 94305-5784. 463 © 2002 by the American College of Surgeons ISSN 1072-7515/02/$21.00 Published by Elsevier Science Inc. PII S1072-7515(01)01179-6