Spring 2011:CellFinder
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Contents
3/14- 3/18 Status Report
This week
- tried to find connectors for rectangular capillaries
- looks like they don't exist, and it seems like we should be able to detect cells using round capillaries anyways, so we'll try that route first (will be easier to interface with the rest of the instrument)
- built an LED circuit using a voltage regulator.
- played around with the phototransistor
- first tried a transimpedance amplifier, but some issues with the op-amp circuit, so we debugged for a while
- we will try to use the other amplification circuit from the DNA melting lab
- it looks like our output from the phototransistor is ~1-10 nA, so we may need quite a lot of gain in our circuit
- ordered things from industrial fiberoptics:
- LED
- phototransistors
- optical fiber
- still need to order:
- epoxy
- solenoid valves
Next week
- finish circuitry for the phototransistor
- start playing around with capillaries/attaching LED and phototransistor to capillaries? (need beads, microscope setup)
- things we will want to answer in the coming weeks:
- effect of capillary diameter on detection sensitivity?
- effect of flow rate on sensitivity?
- effect of bead size on sensitivity?
Risks and issues
- we have little electronics experience, and Jenn needs an electronics review :)
3/21 - 3/25 Status Report
This week
- finished building the electronics circuit
- ended up using DNA melting lab circuit (not the transimpedance amplifier)
- problems associated with electronics:
- high bias from op-amp
- used potentiometer to set bias. originally used one that wasn't very stable, so we switched to the kind that get turned by a little screwdriver
- some noise
- will need to rewire circuit onto better breadboard
- high bias from op-amp
- looks like we get around -5V of signal with maximum signal (putting the LED fiber right next to the photo-transistor fiber)
- started figuring out some sort of setup to hold capillary and fibers in place
- cut holes etc into a piece of plastic with drill and laser cutter
- in short, it's super shoddy at the moment, but we can improve on it in the future
Next week
- set up microscope
- optimize bead flow without our pressure system set up
- hopefully start visualizing flow and setting up the cell sensor part of the instrument
Risks and issues
- I'm scared we won't see anything!
- The sample stage plastic piece we made at the moment isn't super reliable, so we will probably need to design something better to hold everything in place
3/28 - 4/1 Status Report
This week
- set up microscope
- had some software issues, but now it is working
- also the hole we cut into the sample stage thing is on the small side so we don't have a lot of wiggle room, but that will be fixed
- optimizing bead flow
- lots of problems here:
- blocked capillaries (we should buy more soon since we've been playing with the same little pieces too much)
- tried capillary action
- this didn't work either because the polymer is too hydrophobic or it is blocked
- finally hooked up a syringe to our capillary
- lots of problems here:
- visualizing bead flow
- pushed a 1:100 dilution of 1% 15.6um beads through the capillary and visualized with microscope!!!
- concentration seems a little high (lots of beads flowing through at the same time, but maybe we didn't vortex enough?)
- will try a 1:1000 dilution of stock concentration
Next week
- rewire electronics
- set up optics & flow to see what kind of signal we get
- figure out dimensions of our actual instrument (bypass channels etc) so we can buy more capillary tubing
- start setting up pressure system?
Risks and issues
- we will need help and more equipment to modify connections to house pressure
- I'm still scared we won't see any signal
- setup with sensor optics, electronics and microscope might get really gross
