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Voices4/StephanMatopeVanderwaals
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Picking and placing without fingers
Researchers who are developing micro-sized grippers to handle micro-materials have taken a page
out of nature’s book to overcome many of the giant obstacles they face.
Precision engineering with objects hardly visible to the human eye is one such challenge.
“Manipulating the naturally occurring van der Waals forces between micro objects can make them
much easier to handle,” is the solution offered by Mr Stephen Matope, who is busy with his PhD
research in industrial engineering,
Van der Waals forces are the sum of the attractive or repulsive forces between molecules or parts
of the same molecule.
It is the same principle that is in action when geckos effortlessly scale sheer surfaces.
Attraction is clearly advantageous when trying to pick up a tiny object, but becomes a problem when
it is time to release the piece. “When picking up a work piece the Van der Waals forces should be
high, but when releasing the forces should be low”, Mr Matope explains.
Van der Waals forces are affected by the shape, surface roughness and material type of the
interacting objects. “By simply paying attention to the texture and shape of work surfaces and the
microgripper you are using, you can greatly improve the effectiveness with which you handle
micromaterial,” believes Mr Matope.
The advantages of using van der Waals forces are that they are applicable to all materials, can work
in a vacuum, can work in aqueous conditions, do not require an external energy source, and are
suitable for sensitive microchip circuits. They also do not leave residual charges, stresses, strains or
oxide layers on the interacting materials.