Electrical Requirements

MEMS Precision Instruments

The present MICROTWEEZERS have a two pin male connector. The two pins are for the actuator current. The thermal expansion beam is silicon . As it heats up, its resistance decreases. If the power supply is voltage controlled, more current will go through the actuator as it heats up and its resistance decreases. If the voltage setting is high enough, this will continue until the silicon is hot enough to melt. If you are using a voltge source you may want to put a 100 mA fuse in series with the tweezer. It is better to use a current source. Then you set a current (say 80 mA) and this is the current supplied regardless of the resistance of the TWEEZERS . This also helps stabilize the tweezer control since air turbulence can cause random changes in the actuator temperature, and therefore changes in its resistance. Ultimately there will be a servo loop closed by piezo resistors on the tweezer flexures which will have a time constant that is much shorter than fluctuations from air turbulance.

In normal use, the TWEEZER tips will be in focus under the objective lens of a microsope. A positioning stage will be used to bring parts up to the tips. When the desired part is in front of the tips, turn on the current to the actuator to open the tips enough to grip the object. Now move the parts-carrying stage to bring the part between the tips, and turn off the actuator current. The part is now gripped. Lower the parts-carrying stage and move it to the target site. Move the stage as needed to position the gripped part on the assembly being created there. After the part is attached to the target assembly (by inserting into a hole, glue, solder, etc), turn on the actuator current to open the gripper, and lower the parts-carrying stage.


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