DEFCON Micro Fluidics Badge


#1

Hi,
I got approached by folks from the Biohacking Village to create a badge for this year’s DEFCON in August.
The original idea incorporated ECG, but that was something that they had done similarly recently. So after brainstorming a bit, the words Micro and Fluidics came out of my mouth. I may rue the day, but now I’m halfway down the rabbit hole. I had a great conversation with Ryan from DropBot, and have been digging into the designs for OpenDrop V1 and V2.

I’m mostly interested in creating something that is as cheap as possible and can still do something vaguely useful. Of course, getting it to ‘work’ is always a treat! Here’s a basic breakdown of what I’m thinking, based on the OpenDrop V2.

PIC32 microcontroller with USB OTG to run the show. USB will power all the low voltage stuff.
HV507PG interface between low voltage control and high voltage electrodes (ala opendrop).
Rectified and filtered AC mains as high voltage source.

Again, that’s just a high altitude snapshot. ~maybe~ there is an OLED (or other) screen?
I am thinking of a simple software interface to control the droplets over USB. Though there might be a reason to add a joystick on the badge.

The main question that I have is regarding my idea to use rectified mains voltage for the high voltage source. Here in North America, we use 110V AC. Is that enough to move the droplets? As I understand, our 60Hz power signal is too slow to effectively hold and move the droplets, so that’s why I want to rectify it and then drive the HV507 Blanking pin to set the frequency. At least that’s what it looks like OpenDrop is doing.

Also, is there any reason to have a joystick, other than that it’s cool to play with?
Also, OLED or other, screens are cool, and the biohacking village likes bling, but what’s their best use?


#2

If you want to experiment with digitally moving fluids, why not a card in a jar of ferrofluid with a small electromagnet on the top, and another small electromagnet on the bottom? Possibly could put a display in the back even.

Something like:


#3

I don’t have a lot of answers for you because I don’t have any experience with micro-fluidics but am happy to help by reviewing schematics, layouts and firmware, once you have something, as best I can.

Did you find out any answers to your questions?


#4

as we’ll meet-up @gaudi and @kaspar soon. let’s discuss this in more detail during the kitSpring.
also @bengtsjolen was heavily involved in the dev of the circuitry.

greets,
m


#5

Nice to meet ya!
@lucaszw, we’re not talking about ferrofluids, we’re talking about microfluids.
@kaspar, yeah, plz ckeck my work!
@dusjagr, what’s kitSpring?

I’ve got a first pass below. I’m hoping that the rectifier circuit will provide a high enough voltage. It can act as a straight rectifier, or it can be a voltage doubler. Not sure what do do with the OLED, but am keeping it because the client want’s bling. Can someone tell me what the speaker is for?
And, I’ve only modded the schematic. Assume the cheapest rated parts unless specified


#6

@biomurph Ferrofluids + magnets, and electrowetting can both be used for digital microfluidics (as well as opto-electrowetting / dmf snakeskin , dielectrophoresis …) . Here’s a simple example i made w/ 4 nails, magnetic wire, and a little acrylic container:

DMF w/ Ferrofluids (slow motion)


#7

The speaker is so that if it doesn’t work, at least you can play music. @gaudi knows what he is doing :wink: Seriously though, you may be able to use a speaker/piezo buzzer to de-pin droplets that get stuck (i.e., mechanical assistance). There are a few papers in the scientific literature that quantify a reduction in contact line friction due to mechanical vibration.