Electrostatic traps: When photons are too big

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In their quest to study ever smaller and smaller particles, scientists have hit on particles too small even to be captured in a wavelength of light. What can you use to trap these particles? Meet the electrostatic trap.

An older post on Io9 discussed optical traps as a way to deal with particles too small or delicate to be held with conventional fixing materials. Optical manipulators trapped such particles in beams of light. If the particle were to wander one way, the beam of light would be diverted outwards, and kick the particle back to the middle of the beam. The post made much of how current science was entirely too involved with small things.


It looks like scientists have broken the teeniness barrier, and are looking for equipment to catch up. Not even light will do it, anymore. If the particle is too much smaller than the wavelength of light, the light will blow right by it instead of being diverted, and the particle will be able to break out of the trap.


Newly designed to take care of just such an emergency is the electrostatic trap. The trap is simple: two plates of glass separated by a liquid. Small grooves are carved into one plate.

When glass comes into contact with water, the glass gains a negative charge. Exposing the two plates of glass to water will therefore give them a negative charge. Since both of them are negatively charged, they will repel each other.
They will also repel any negatively-charged object put between them. The object will swim around the fluid between the plates, basically ping-ponging between the sides. Until it hits one of the grooves. Since the groove means one plate is farther away, there will be a little area where the negative charge lessens. Once the object slips into this area, it won't be inclined to wander out, since every direction will mean an increase in negative charge.


The trap can keep a particle in that small area for hours, giving scientists a chance to study it. I'm assuming it's too small to be studied with comically oversized magnifying glasses, but since that can be the only comfort in not being able to trap things with lasers anymore, I imagine that that's what the scientists will use.

Via Physics World and JCP.