DIY Laser tweezer, cell trap, oligo synthesis

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Trap Sprint.jpg

In a short and intense hack sprint we tried to reproduce the laser tweezer as described in the paper of A. Kasukurti, M. Potcoava, S.A. Desai, C. Eggleton, and D. W. M. Marr1,* - found here:
Single-cell isolation using a DVD optical pickup
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3169297/
To do so, a group of bio hackers, micro engineers, artists and theoretical multi dimension algebra mathematician and a few lovely cats met in the FarmLab in Clemens near Lausanne.

Trap cats.jpg

Harvesting the Laser

First we needed to harvest the lasers from old DVD Drives (Digital Versatile Disk).
For the experiment we need strong lasers found in DVD Burners with speeds 16x and up.
To know what you have got at hand, the following list is pretty helpful:

Trap Laser type.png

Source: http://elabz.com/laser-diode-power-output-based-on-dvd-rrw-specs/

Trap Laser.jpg

Everyone working hard to screw open the DVD housing. In the exterior plastic housing we found a metallic frame with the laser unit on a sled.
We removed all down to the laser sled, keeping together the metal cast with the laser diode and the lens with focusing mechanism.

As a backup we also ordered and used some laser units from https://hightechdealz.com
4 x 650nm 20x DVD Burner LPC815 Sled (LPC815) = $41.24

Trap Lasersoldering.jpg

Once the laser were extracted we soldered wires directely on the pads of the laser diode and the focusing mechanism.

Trap Laser pinout.jpg

We found that the existing wiring (flex cable) does not need to be removed. Just cut the connections off to avoid interference with the existing ellectronics.

Powering the Laser

The powering of the laser turned out to be not so easy as the lasers are very sensitive to over current (and maybe shock).
The power supply we used first to power the leds was probably not stable enough and killed some lasers. This can be very annoying when the lasers are already integrated in some mechanical setup.

First Notes:
- The schematic in the papaer to power the laser uses an "unusual" pinout of the LM317. Refer to the schematic below rather.
- The suggested current of 350mA for a DVD laser diode is at the upper limit of what most of these laser can take (without extra cooling). So go slowly and expect to blow up your diode at 350 mA (what happend to me)
- Actualy the discription of the diagram in the paper says 420 mA. When I recalculate the current (with R=4 Ohm and UAdj=1.25V (I=UAdj/R) I get a current of only 312 mA. This is probably a good value :-)
- Generaly laser diodes are quite delicate. When they suddenly get less bright then they are in the so called "LED" mode and kaput.


Trap schema.jpg

R=4 Ohm (in total) Pot= 100 Ohm or less.
We found the original schematic as described in the paper to work well and reliably. We powered it with a 4 1.5V batteries in a battery holder with on-off switch.

Trap board.jpg

Electronics solder on a board.



Trap coils.jpg


Mechanical Setup

Trap Setup def.jpg

Trap Setup1.jpg

Trap PictureSetup1.jpg

Trap Setup1 result.jpg

Trap Setup2.jpg

Trap PictureSetup2.jpg

Trap Setup3.jpg

Trap PictureSetup3.jpg

Trap Setup4.jpg

Trap PictureSetup4.jpg

The objects to move arround

Trap Beads10.png

Trap Beads15.png

Trap Centrifuge.jpg



Optical tweezers directed one-bead one-sequence synthesis of
oligonucleotides†
http://www.ncbi.nlm.nih.gov/pubmed/21445444

Interferometry with optical pickups.
Quercioli F, Tiribilli B, Bartoli A.
http://www.ncbi.nlm.nih.gov/pubmed/18073818

A CHEAP 2D FLUORESCENCE DETECTION SYSTEM
FOR μM-SIZED BEADS ON-CHIP
Loes I. Segerink*, Maarten J. Koster, Ad J. Sprenkels, Istvan Vermes and Albert van den Berg

A new DNA chip detection mechanism using optical pick-up actuators
Kyung-Ho Kim, Seung-Yop Lee, Sookyung Kim, Seung-Hwan Lee and Seong-Gab Jeong
http://www.springerlink.com/content/084133p3n5mk1411/