Less friction from stiction

Micro-electro-mechanical systems, or MEMS, in small electronic devices often fail because of adhesion and stiction, the attractive force between the surfaces of interacting parts.

researchers have developed a surface-topography engineering method that reduces these forces and will help microscopic parts interact and function smoothly.

‘There are two approaches to address adhesion and stiction issues in MEMS devices,’ said Min Sou, assistant professor of mechanical engineering. ‘One is chemistry – applying chemicals on surfaces to weaken the forces. The other is topography engineering. Our approach was simple. We engineered nanoscale bumps to reduce the contact area between surfaces.’

The goal of the project was to create a hydrophobic surface. Determined by a popular engineering benchmark known as the water-contact angle, hydrophobicity describes the process of water ‘beading up’ or turning into a ball, such as rain does on an car windscreen that has been treated with chemicals. The water-contact angle is the measurement used to describe the extent to which water beads. A water-contact angle greater than 90 degrees is considered hydrophobic, and any angle greater than 150 degrees is considered superhydrophobic. With a water-contact angle of approximately 180 degrees, beads represent a near-perfect sphere with only minimal contact on surfaces.