On Mon, Oct 5, 2009 at 12:44 PM, Albert Henning wrote:
> 1) what's the application?
diagnostic chemistry/biology work
> 2) what's your specification?
fluidic channels will be from 5 - 20 microns wide, most likely
> 3) what's wrong with plastic or similar? That is, what in your spec
> demands something non-plastic?
plastic would be OK, as long as I could still implement some wiring
and the devices I mentioned, as well as potentially a few others.
Maybe silicon would be better to work with in general, if I factor out
needing the device to be optically clear in which case I would need to
implement a laser/LED in the chip.
> 4) what's 'right' with germanium oxide? My goodness, that's an exotic
> material. Growing a stable oxide on single-crystal germanium is
> extremely difficult, requiring both I think high pressure and high
> temperature (the original investigations date to the 1950s), and even
> then the oxide is pretty much crap as an electrical insulator, and who
> knows about its mechanical properties.
Hmm, I was just thinking GeO2 because its transparent to more light
than Si glass.
> 5) people have built a wide variety of pumps and pressure sensors out of
> plastic. I'm less sure about glass (can't recall any offhand, although
> I've built glass membranes, and have seen some publication of same in
> the literature).
Oh? I would appreciate some author names or paper cites... My main
concern is the scalability of this project, in the long run if I
wanted to start a small manufacturing venture for a device, would
silicon or plastic chips be cheaper? I would think there would be a
lot less capability with plastic, but less disposability with silicon
(unless I came up with a way to clean silicon channels using
mechanisms present on the chip itself... i.e. a cleaning solution pump
circuit.
> 6) Far more pumps and pressure sensors have been built out of silicon,
> or combinations of silicon and glass. Quartz (crystalline silicon
> dioxide) has been used for resonant pressure sensors for a long time,
> although not so much in MEMS.
Mmm, I will be taking a MEMS course in the spring, I want to take it
this winter, but unfortunately my schedule conflicts.
> 7) Alignment of channels can be done using KOH-etched silicon at a
> specified width, then use optical fiber as a 'guide' for alignment on
> bonding. Numerous schemes exist for the actual bonding (Si-glass,
> Si-Si, glass-glass, using metal as intermediary bonding layer; Goran
> Stemme at KTH and his colleagues used a particular bonding resin with
> good results). This is a low-cost and relatively high precision
> alignment scheme, and has been published in the literature.
Do you mean fiber optic cable? The channels would likely not have open
ends to allow this, I think it better to have alignment marks etched
into the chip, and be positioned under a microscope, but maybe not.
> 8) why a cylindrical channel?
I need to mimic blood vessel capillaries, which are more round than
square, no sharp edges.
> Look around on Google scholar for references on materials and
> processing. Peter Woias has a particularly good review on micropumps,
> about 6-8 years ago. But, there's been considerable new work in the
> interim. Look at the journal Lab on a Chip, and the proceedings from
> the micro-TAS conference.
Yeah the lab on a chip journal is a good one, they have good tips.
I'll check the others out soon, thanks!
> If you want to prototype something quickly, look at Steve Quake's
> foundry at Stanford. You could build a pneumatically-actuated
> bucket-brigade pump out of his tech, and kluge up a pressure sensor from
> deflection of a PDMS membrane.
>
Will do, I have a micro lab at my disposal here, even with ion
implanter, so the sky is almost the limit (really more limited by my
knowledge of intense math equations to figure out all the engineering)
> Albert K. Henning, PhD
> Director of MEMS Technology
> NanoInk, Inc.
--
Nathan McCorkle
Rochester Institute of Technology
College of Science, Biotechnology/Bioinformatics