Microarachnophobes might want to avoid this article from Ferris Jabr and the New Scientist. Others, please enjoy. Cheers, -DGA
A new spider-like micromachine could swim through a person's blood vessels, healing damaged areas and delivering drugs as it goes.
Ayusman Sen of Pennsylvania State University in University Park and his colleagues have created the self-propelling microspiders using spheres less than a micrometre wide. Each sphere is made up of two halves – one hemisphere is gold, the other silica – and looks like a gold-and-silver Christmas bauble.
To turn the spheres into motors, the group attached a Grubbs catalyst – a molecule that builds long chains of smaller molecules – to the silica side. When Sen drops his spheres into a solvent containing the chemical norbornene, the catalyst spins a polymer from molecules of the chemical. Eventually there are far more unpolymerised single molecules of norbornene around the gold side of the sphere than the silica side , creating an osmotic gradient, as fluids will always move from a region with lots of particles to a region with fewer particles. The solvent rushes toward the gold side of the sphere, causing the whole sphere to move.
Sen's group were able to control the direction of the spheres' movement by placing lumps of gel soaked in norbornene at one corner of the tank of solvent. The thread-spinning spheres followed the trail of leached norbornene towards the gels.
Next, Sen hopes to develop versions of these tiny aquatic spiders that run on chemicals readily available in the body, such as glucose. In the future, more sophisticated microspiders attached to nanobots that detect chemicals secreted by damaged tissue could swim through the bloodstream, weaving a medical glue to help heal tears in vessel walls. Decorated with other micromachines and enzymes, they could swim through the circulatory system scouting out tumours, scouring plaque from vessel walls and helping the immune system battle infections .
The microspider represents a “new model of micromachines based on chemistry”, says Joseph Wang, a nanoengineer at the University of California, San Diego, in La Jolla. “It's the first example of a micromotor that works on polymerisation. The concept is preliminary, but when it is improved it could be very powerful.”