Microgripper

The manipulation of biological objects is usually performed in a life-sustaining environment, where electrical fields or thermal gradients in the liquid may cause perturbations. Therefore we developed a mechanically actuated microgripper fabricated in silicon by a combination of bulk and surface micromachining processes, that exhibits several advantages compared to other approaches. The concept of the gripper was first studied by performing extensive simulations using a finite element simulation program. The expansion of two piezo bars, constituting the motor, provides the mechanical force required to close the tips of the gripper. This force is translated along a copper wire to the microgripper. The micro-motor, consisting of the piezo motor and the microgripper, is attached to a MM3 Kleindiek Micromanipulator, a high precision positioning tool with nanometer resolution. The function of the gripper was proven and manipulation tests of spheres with 5 µm diameter were performed by grabbing, lifting and releasing them on a gold coated surface.
A real time detection method of the moment of grabbing was tested. The method is similar to the one used in atomic force microscopy, only here the torsion of the tips when exerting a grabbing force on the object is detected with a laser beam and a photodiode.

Scanning electron micrographs of the microgripper

Manipulation of a 5 µm sphere on a gold-coated substrate