Fluid Logic Chips 250
Doc Ruby writes "Colorado researchers 'have constructed microfluidic gates that use the relative flow resistance of liquid to carry out the basic logic operations NOT, AND, OR, XOR, NOR and NAND. The researchers have also combined a pair of gates into a half adder, which carries out half the operation of addition.' All CPUs processing binary logic are made of these types of gates, but usually execute as flows of electrons in wires, not fluids in tubes. Will this advance revolutionize chemistry and computing the way electric gates revolutionized electronics and computing? Will 'fluid programmers' give new meaning to "flowchart"?"
Old logic, new gates (Score:2, Informative)
In Eastern Germany (Score:5, Informative)
Essentially it worked the same way, plus they had a little "Transistor" where a big airstream would be disturbed if a small control airstream is on.
Obvious advantages of that technology:
- You only need to be able to cut sheetmetal and weld it together
- Not affected by X-Rays unless you melt it (think MAD/Nukes)
- Probably no cooling problems (not sure about this)
Of course, it'd be also very slow. And big.
Re:How fast? (Score:5, Informative)
How would you cool such computing devices? (Score:3, Informative)
Comment removed (Score:3, Informative)
Re:Sounds great but... (Score:5, Informative)
The flows here are created by the capillary forces which dominate at that size.
No gravity required.
Fluid computer in Cold War? (Score:3, Informative)
Re:How fast? (Score:5, Informative)
The speed of light in a material is slower than in a vacuum, by a factor of the index of refraction (usually frequency dependent). Interestingly, it IS possible for particles to travel faster than this apparent speed of light, and in doing so they emit Cerenkov Radation [wikipedia.org], which is how many high-energy physics particle detectors (eg SNO) detect individual particles.
** For the nitpickers who will inevitably respond to that generalization, it is occasionally possible (in theory, at least) to set up a mode in some carefully-devised system where the speed of propogation of this mode is faster than c, but this mode cannot carry information. Simple example is a linear array of equally-spaced pendula, each with the same fundamental frequency, and with a spring connecting the weights at the bottom to the two pendula on either side. If a mode is set up where all pendula are oscillating at their fundamental frequency, all of them at exactly the same phase, (springs always remain at their unstretched length) then the phase velocity of this mode is infinite. However, there can be no 'information' or disturbance transmitted down the system. In reality, thermal and quantum disturbances would disrupt this mode and it would eventually become something much more complicated. These disturbances would be transmitted at a finite velocity, less than c.
Re:How fast? (Score:5, Informative)
You can quantify that better. It basically travels at the speed of sound in the medium, because it uses the same forces that sound does.
This is also the solution to the relativity paradox, "What if I take an infinitely rigid rod and tap it on one end, causing the other end to instantly vibrate, with the tap exceeding the speed of light?" The answer is that in this universe, no such infinitely rigid rod is possible; the maximum speed possible is still the speed of light.
This also implies that fluidic computing will always be slower than electronics, because the fundmental speed is orders of magnitudes slower. Which doesn't mean it is useless, I'm just killing two birds with one stone here, showing why this is no threat to electronics
Re:How fast? (Score:5, Informative)
This seems to be a common misperception on slashdot.
Electrons are certainly used, of course, in digital logic circuits. For example representing bits as charge stored in a capacitor, or by mediating the quantum statistics of a transistor for switching (by controlling the charge on the gate of a MOSFET).
However - when a signal is sent down a wire (eg, from a microprocessor, over the data bus, to a peripheral) that signal is NOT being sent through the electron drift. [Although electrons will drift in presence of an electric field, the drift velocity is INCREDIBLY small, look it up.]
If the microprocessor wants to flip a bit from a 0 to a 1, the wire is originally at one potential, and the microprocessor will change the potential. This disturbance isn't instantaneous along the wire, that would violate relativity. The microprocessor basically creates an electromagnetic disturbance that travels down the wire to the peripheral.
Now let's look at this 'disturbance' more closely. Electrons at point A are being ultimately effected by electrons at point B. This effect is mediated through electron interactions, and one knows that that the electromagnetic force is the mediator between electrons. And from Quantum Field Theory one knows that photons are the quanta of the electromagnetic force.
So what this in effect means is that whenever electrons are interacting, photons are being transmitted somewhere during that exchange. Thus, the parent was correct that it's the electromagnetic wave, as opposed to the physical motion of the electrons themselves. that plays the role in limiting digital logic speed.
Fluidic state machine: automatic transmissions (Score:2, Informative)
One link I found (go down to "Valve Body"):
http://www.familycar.com/transmission.htm [familycar.com]
The modern processor is an electrical state machine and the valve body is a fluidic state machine.
The only real development is the physical implementation of the logic but considering that currently they can't link gates it's not of that much practical use since you can't form a state machine (or anything more complex than a gate)...at least I'm not aware of a way to make one layer of logic a state machine...
Cool nonetheless.
Re:How fast? (Score:5, Informative)
Actually, if you look at the microscopic physics, they both use the same forces. It's primarily electromagnetic forces, although some quantum degeneracy statistics plays a role too, that prevent your hand from going through a door when you knock on it. However, in fluidics (and sound) phonons are being transmitted through the medium, just like photons are transmitted through the wires in electronic systems. However, the sound waves derive mostly from the usually harmonic potentials keeping molecules spaced apart at their average distances. EM waves derive from charges (ie, electrons) moving and reacting with each other.
This also implies that fluidic computing will always be slower than electronics
Practically yes, but to be pedantic - not necessarily always. Maxmimum signal speed in fluidics would by governed by phonons, and in electronics by photons.
In reality the phonon modes, which are usually pretty dispersive (ie propogation speed depends on frequency), have slower propagation speeds than photons (also usually dispersive but usually not as much) in most matter.
But to say 'always' isn't necessarily true, there's no reason a priori to assume in some random material photonic excitations are necessarily faster than phononic excitations.
Missing the point, perhaps? (Score:2, Informative)
This stuff will not WILL NOT ever replace electronic circuitry. I don't think anyone who works with microfluidic applications would seriously claim this. There is just too large of a speed differential between fluids and semiconductors. Do you want your computer making decisions on the millisecond time scale (fluidics) or the subnanosecond time scale (silicon)? This work is a little misguided, and somewhat misleading as it tries to mimic electronic circuitry. Fluidic logic was rightly given up as a techy-backwater thirty years ago. There is tremendous potential in this field, however, when people start to think out of the box of usual engineering.
There are some really cool fluid physics that take over at these length scales. You can't have turbulence (the Reynold's number is far too low) so neighboring streams are totally laminar, and stay separate until they mix by slow diffusion. Buoyant forces dominate over convective forces (the Grashoff number is low), so you can do biology and chemistry experiments in these systems that were previously only practical in microgravity. For a tiny fraction of the cost, mind you... most microfluidicists use a channel-making process that employs photolithography, so you can use the economy of scale to do a f^Hckton of experiments for pennies on the dollar. Better than hoping your precious bugs survive the next shuttle flight.
This stuff is already having a serious impact in biotech and big pharma. The Human Genome Project wouldn't have been possible without technology that used these physics to shunt little packets of fluid around. Synthetic chemists use it to make thousands of variations on whatever drug they're working on.
Do some googling if you're interested... the field is booming right now.
Oh, and these guys are almost certainly using computers to drive their input pumps. Cheating, sorta...
Re:How fast? (Score:1, Informative)
The signal, of course, is propagated much faster.