Convergence, market opportunities drive micro

The following is an interview with Stefan Dimov, Ph.D., professor of advanced manufacturing technology and research director of the Manufacturing Engineering Centre at Cardiff (Wales) University. He is also head of MEC’s Micro and Nano Manufacturing Program. Dimov joined the MEC in 1993 and has been a principal and co-investigator in more than 50 R&D projects. He is the author of more than 150 papers and the co-author of two books.

Stefan Dimov, Cardiff University

MICROmanufacturing: You have devoted a substantial portion of your career to the study of micromanufacturing. How did you first develop that interest?

Dimov: In the late 1990s and early 2000s, the MEC was looking for new hot spots in R&D where we could deploy our expertise in precision engineering. We visited manufacturing centers in Germany that had made major investments in micromanufacturing outside of what had been done in the semiconductor industry. We became very interested in this area, and we felt we could leverage our expertise in laser milling in this new area. We proposed the Micro and Nano Manufacturing Program at Cardiff, which is now 10 years old.

MICRO: What are the most important recent developments in micromanufacturing technology?

Dimov: Convergence has been a trend for the past 5 years, both in terms of horizontal and vertical integration. Horizontal integration is bringing together complementary micro technologies, like milling, laser milling and EDM milling. The idea is to determine the best application and/or cost-effective processing window for each method so you can combine their capabilities in novel process chains. Vertical integration is achieved by “aligning” several different technologies in a specific application area, thus creating new manufacturing platforms. After conducting feasibility studies, carrying out validation programs and going through pilot applications, some companies are using these platforms to underpin next-generation products. For example, RSP Technology in Holland has developed a refined aluminum that has a very favorable machining response and which can be used to produce molds with a surface quality two times better than conventional aluminum. It is ideal for micromanufacturing, among other applications.

MICRO: Which developments hold the most promise for commercialization?

Dimov: We are looking for complementary technologies and most of our research focuses on making masters (tools) for one-to-one microreplication processes, such as thermal and UV imprinting, hot embossing and injection molding. For example, milling, laser ablation, EDMing and electroforming are all important for masters making. Focused-ion-beam technologies can be used to make relatively shallow features smaller than 10µm, and even submicron features.

MICRO: What are the major growth sectors for micropart manufacturers?

Dimov: Micromanufacturing plays a major role in life sciences, energy, and display and lighting, and all three are growth areas. Biosensors (also known as point-of-care and lab-on-a-chip products) employ micro optics and fluidics to get on-the-spot results for medical tests from very small amounts of fluid. In energy, micro fuel cell development is growing. In lighting, application of micro-optics-based LED displays has become an important business.

MICRO: What are the challenges micromanufacturers face when measuring micro parts, machining work materials and handling parts?

Dimov: First, there are no tolerancing standards for micro applications. We are still using tolerancing standards developed for macro applications, and these standards usually do not carry a proper uncertainty analysis of micromanufacturing technologies. This makes it difficult to define products’ technical requirements and then to determine whether or not a micromanufacturing process and components fabricated with it are viable. The standards need to be changed. Most product developers are not engineers—they are physicists and chemists creating drawings with nominal dimensions but without properly assigned tolerances. They need standards to assist them in the design process.

Regarding your second question, we typically use workpiece materials developed for some other applications, but which can be used for micro scale applications, too. The volumes involved in micro are usually too small to make it attractive for the development of micro-specific materials, or the high cost of a specialty material means the cost of the finished product has to rise substantially. Also, we need to develop processes that minimize the use of expensive materials in micro products. For example, point-of-care and lab-on-a-chip products include disposable components, so it is necessary to produce them from relatively low-cost “bulk” materials or just to deposit a limited amount of a more-expensive material on the surface of a less-expensive substrate, just sufficient to produce the necessary functional features and structures. That’s what the semiconductor industry is doing.

Regarding part handling, assembly is the dominant process for integrating functions in products, but we have to look for other ways to integrate functions. Assembly is difficult and expensive in the micro world and has to be the last resort. We need to integrate functions by depositing materials and by machining or replicating scale features and structures of different lengths in a single component to achieve the same result you get by assembling components.

MICRO: You have played an important role in the International Conference on Multi-Material Micro-Manufacture (4M) and the International Conference on Micro-Manufacture (ICOMM). How have those conferences helped advance micromanufacturing? What are the differences between the micro research communities in Europe and the U.S?

Dimov: In Europe, the 4M conferences have brought together technology and application specialists and researchers. We were talking earlier about convergence, a phrase coined by the 4M community. This has helped micro product developers realize they must consider the whole spectrum of competing and at the same time complementary technologies when they develop products. The other important outcome is the creation of a critical mass of knowledge. There is a lot of niche knowledge in research centers spread across different organizations and universities, but they often don’t have a critical mass in their own institutions. Thus, by bringing together researchers, the confidence level increases. In my opinion, there is one significant difference between the 4M community in Europe and the ICOMM community in the U.S. The 4M community includes MEMS researchers, and we work together, which broadens the range of materials and technologies under discussion. My understanding is that this is not the case in the U.S., where the MEMS community has their own research groups and usually gathers at different events. From our experience, there are major advantages to working together. µ