Ingenieur Vol 77 Jan-Mar 2019 ingenieur 2019 Jan-March | Page 26

INGENIEUR on the one hand the envisioned use of nano- particles inside the body and the blood stream (for diagnostic and therapeutic purposes), and on the other hand – potential development of new weapons of mass destruction enabled by nanotechnology. Current products of nanotechnology are much more ordinary – reinforced plastics for the bicycle frames, stain-resistant clothes, better cosmetics and healthcare products, and tennis rackets reinforced with carbon nanotubes. An emerging field within nanotechnology is known as bionanotechnology, which is a synthetic technology based on the principles and chemical pathways of living organisms. Bionanotechnology looks for connections between molecular biology and nanotechnology – guiding the development of machinery at the nano-scale by the structure and function of natural nano-machines found in living cells. As was the case with many new technologies, solid predictions of their course of developments are difficult to make. If nanotechnology were to follow the paths of other new technologies (digital communications, the Internet, etc.) the early predictions – for the first ten years – would tend to overestimate the impact of the technology (much less is achieved compared with predictions). However, the long-term prediction – for the first 50-75 years – would tend to underestimate that impact (much more is achieved compared with predictions). Micro –Electro-Mechanical Systems - MEMSnet Micro-Electro-Mechanical Systems, or MEMS, is a technology that in its most general form can be defined as miniaturised mechanical and electro-mechanical elements (i.e. devices and structures) that are made using the techniques of microfabrication. The critical physical dimensions of MEMS devices can vary from well below one micron on the lower end of the dimensional spectrum, all the way up to several millimetres. The types of MEMS devices can vary from relatively simple structures having no moving elements, to extremely complex electromechanical systems with multiple moving elements under the control 6 24 VOL 2019 VOL 77 55 JANUARY–MARCH JUNE 2013 of integrated microelectronics. The one main criterion of MEMS is that there are at least some elements having some sort of mechanical functionality whether or not these elements can move. The term used to define MEMS varies in different parts of the world. In the United States they are predominantly called MEMS, while in some other parts of the world they are called “Microsystems Technology” or “micromachined devices”. While the functional elements of MEMS are miniaturised structures, sensors, actuators, and microelectronics, the most notable (and perhaps most interesting) elements are the microsensors and micro-actuators. Microsensors and micro- actuators are appropriately categorised as “transducers”, which are defined as devices that convert energy from one form to another. In the case of microsensors, the device typically converts a measured mechanical signal into an electrical signal. More recently, the MEMS research and development community has demonstrated a number of micro-actuators including: microvalves for control of gas and liquid flows; optical switches and mirrors to redirect or modulate light beams; independently controlled micromirror arrays for displays, micro-resonators for a number of different applications, micropumps to develop positive fluid pressures, micro-flaps to modulate airstreams on air foils, as well as many others. Surprisingly, even though these micro-actuators are extremely small, they frequently can cause effects at the macroscale level; that is, these tiny actuators can perform mechanical feats far larger than their size would imply. The real potential of MEMS would be fulfilled when these miniaturised sensors, actuators, and structures are merged onto a common silicon substrate along with integrated circuits (i.e., microelectronics). Although MEMS and Nanotechnology are sometimes cited as separate and distinct technologies, in reality the distinction between the two is not so clear-cut. In fact, these two technologies are highly dependent on one another. The well-known scanning tunnelling-tip microscope (STM) which is used to detect individual atoms and molecules on the nanometre scale is a MEMS device. Similarly, the atomic force microscope