Module 10 : Futuristic topics in robots
Lecture 38 : MEMS- II
  Laser Micromachining
Mechanism:
 
Pulsed Laser beam with focusing optics are focussed on surface to be machined with focal point kept on the surface. High energy is delivered in pulsed fashion to remove material (micro/nano second pulses, recently femtosecond pulses).Lesser is the period of pulse higher will be the accuracy as we are giving energy in a shorter time material doesn't get chance to spread that energy. This results into localised effect. Here we use High precision XY movement of the substrate to achieve the desired cut.
  Advantages:
Microcuts on complicated 2D shapes possible.
This is Maskless process. hence it will bring down the cost of process.
Minimal heat input.
Minimal damage to microcomponents fabricated as the area getting affected around the cut is very short.
Variety of materials can be processed.Nd-YAG LASER with high power (150-200W) and wavelength (1064nm) facilitates fabrication of non-metals (ceramics) and metals (sheets of thickness 50-200 m m or even more). We cannot use Nd-YAG LASER for polymer material as these are high power which will affect accuracy. So we will use Excimer LASER for for processing polymer materials to very fine dimensional accuracy.
 
  Now we see use of these fabrication techniques to fabricate micro-robots.
Microgrippers and micromanipulators
Several microactuators which can be used in future micro-robots.We will see actuators which are not currently in use but have a potential for their use.
 
Novel mobile micro-robots(Scratuator).
  Micro-grippers, Micromanipulators :
 
Figure 38.3
  Principle is based on electrostatic actuation using comb drives. Comb drives are actually comb like structures whose teeths on either side are in mesh with teeths of another structures. When the voltage is applied across gold contact pad, due to electrostatic force of attaraction, teeths there is movement at gripper end.This is basic principle.From fabrication point of view these structures are freely moving structures which are anchored at base. These are just like Cantilever the only difference is that comb like structures are protruding out along the length. As gold is having better electrical conductivity use of it as a contact pad is done.
   
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