Special Issue: 15 Years of SU8 as MEMS Material

In 1997, the first paper using SU-8 as a material for microfabrication was published [1], demonstrating the interest of this negative photoresist for the near-UV structuration of thick layers and the manufacturing of high aspect-ratio components. SU-8 quickly became a cheap alternative to X-ray LIGA, at least for applications that did not require the extreme aspect ratios and precision that can be achieved with X-ray lithography. The possibility to pattern easily multilevel structures of SU-8 [2] expanded significantly its range of applications and led to its early adoption by the industry. In the last 15 years, the interest of the MEMS community for SU-8 has never declined. SU-8 has been used for the manufacturing of a wide range of components in all application areas of microtechnology. After 15 years of use of the SU-8 resist, it is time to look back at the road travelled: This special issue of Micromachines is dedicated to SU-8 as MEMS material, and its developments in terms of processes and applications. This special issue presents a total of twelve papers that cover a large spectrum of processes and applications of the SU-8 material and includes papers related to established techniques used for industrial production as well as articles dedicated to innovative processing techniques and new potential application areas of this resist. Three of the papers are review articles, focused on different aspects of SU-8. One in particular focuses on industrial applications of SU-8 in the UV-LIGA process [3] and not only describes the primary use of SU-8 for the production of molds, electroplated microparts and multilevel components, but also addresses the fabrication of functionalized parts using inserts and the integration of diffractive optical elements. Mimotec SA, the company from which this paper originates, has its entire manufacturing chain centered on the SU-8 material and it is of particular interest for all SU-8 users to have an industrial perspective presented in this special issue. Another paper reviews non-standard techniques that can be used for processing SU-8 [4]: inclined and backside photolithography, drawing lithography, holographic interference lithography, two-photo absorption lithography and moving mask OPEN ACCESS