Actuator Demonstrated in Optical Switch

Hank Hogan

An ideal microelectromechanical actuator would combine performance and economy. Researchers from the Electronics and Telecom Research Institute in Taejon, South Korea, have developed a laterally driven electromagnetic microactuator that may fit the bill. They recently demonstrated the device in a 2 x 2 optical switch.

In South Korea, researchers have demonstrated a laterally driven electromagnetic microactuator in a 2 x 2 optical switch. The actuators require only a simple fabrication process, the team says. Courtesy of Jong Soo Ko.

The heart of the actuator is an arch-shaped spring less than a millimeter long. That small addition pays big dividends, said researcher Jong Soo Ko. "It's a simple structure and very simple fabrication process," he noted. "That means a low production cost."

The arch bows to the right or left and connects to stationary pads at both ends by U-shaped structures. The actuator sits atop a magnet, so that when current flows through the device, the magnetic field generates force and deflects the spring. The spring snaps to a new position -- for example, from a rightward to a leftward bow -- and remains there as long as sufficient current is applied. When the current stops, the spring snaps back.

To demonstrate the utility of the actuator design, the researchers constructed prototype optical switches. They mounted micromirrors on leaf springs, which could be switched through a 60-µm deflection. The fabrication process required less than 24 hours, and Ko noted that optimization could drastically reduce production time, effort and expense.

The leaf springs are a sandwich of polycrystalline silicon and aluminum, making the devices resistant to shock and fatigue. They continued to work after the group subjected them to a 1-m drop test on a cement floor and to 1 million oscillations.

Ko and others are working to understand the spring snap-through and hope to create practical micromachines based on the actuator. "From now on, we have to design and fabricate some devices for real applications," he said.