**7. References**


**6** 

**Surface Characterization and Interfacial** 

The characteristic size of MEMS is ranging from atomic and molecular scales to micrometer and several millimeters scales. Components that reach micro-scale size have a high surface to volume ratio, which leaves them be highly subjected to micro-scale effect and susceptible to surface forces. Devices that utilize MEMS technology will often having mating surfaces. Adhesion force can arise from any number of phenomenon such as van der Waals, capillary, ionic and molecular forces. The components used in MEMS structures are very light (on the order of a few micrograms) and operate under very light loads (on the order of a few micrograms to a few milligrams). Surface forces between the adjacent surfaces are becoming dominant over the inertial force in MEMS devices. Because of the micro-sized component, the adhesion forces can pull the adjacent compliant structure into contact and result the interfacial adhesion, which may cause the device-malfunction to a great extent. The operation and performance of lightly loaded micro/nano components in MEMS are highly dependent on the adhesive interactions between mating surfaces. In a word, it is important that the mechanisms of interfacial adhesion should be explained, and separating techniques should be added to the design of MEMS scale components to ensure there is no unwanted contact. Furthermore, the interfacial adhesion between two adjacent mating surfaces is determined by the interaction of rough surfaces. The surface is all rough though in different range. The interactions among different asperities are complicated because the surface topography is consisting of so many asperities. It stands to reason that the proper surface

The interfacial adhesion is the science and technology of two interacting surfaces in relative motion and of related subjects and practices. It is also valuable in the fundamental understanding of interfacial phenomena to provide a bridge between science and engineering in MEMS. The differences between the conventional or macro-contact and micro/nano-adhesion are contrasted in Table 1. In macro-contact mechanics, tests are conducted on components with relatively large mass under heavily loaded conditions. In these tests, contacting between mating surfaces is inevitable and the bulk properties of mating components dominate the contacting performance. In micro/nano-adhesion, measurements are made on components, at least one of the mating components, with relatively small mass under lightly loaded conditions. The interaction is not limited only to the contacting condition. In this situation, though without contact, the attractive interaction

characterization is necessary to elucidate the interfacial adhesion.

**1. Introduction** 

**Adhesion in MEMS Devices** 

Y. F. Peng and Y. B. Guo

*Xiamen University* 

*China* 

