Lasertweezer – Optical Trap

I just used L272M today (I'm experimenting with sinusoidal stepper drivers). It's a dip8 1A dual opamp, commonly used as motor driver. Quite unobtainium these days. Lcsc only have L272D version which is soic16. I got mine as a fake (but functional) "black top" from AliExpress.

Amazing that this can be achieved at such a low cost. The DVD optical pickup is truly a marvel of engineering, incorporating fairly complicated optics into such a small space. The focusing lens additionally has a electromagnetically controlled suspension system for adjusting the focus, so in theory you should be able to achieve z positioning of the microspheres as well. It would be great if the red dvd laser could be filtered out and the microscopic fluctuations of the trapped particle could be imaged with the camera to estimate the trap stiffness.

A similar optical pickup made of optical components from newport or thorlabs would run you a few thousand dollars, whereas these dvd optical pickups can be had for $10-20.

Here is another great paper (and accompanying youtube video) that shows optical trapping, atomic force microscopy, and even imaging with a dvd optical pickup.

https://pubs.acs.org/doi/10.1021/acssensors.8b00340

https://www.youtube.com/watch?v=5bqujaldaCQ

That's pretty cool!

One of the nice things about hanging here, is seeing posts like this.

Of course, I suspect that I'll never have a use for this, myself.

I have always seen manipulation at this scale done via micromanipulators (wire bonder or inside of a vacuum chamber)

When you need precision movement, the alternative to micromanipulation is using a XY stage like ASML uses.

XY let's you hold an object like a wafer or part, and move it around in certain planes while not moving in others. XY and even XYZ stages are not uncommon in vacuum chambers where parts need moved but repeatability is key.