Electro-osmosis: pumping water with electricity and no magnets--make money online

today on Applied Science I'm going to

show you how to build a pump in which

the only moving part is the liquid

itself and it functions as a flow sensor

and it doesn't use any magnets so until

I said that last part you may have

recalled the movie The Hunt for Red

October in which there's this fictional

sounding but actually quite realistic

thing called the magneto hydrodynamic

drive which is a long name for something

that's actually fairly simple you know

that if you pass a current through a

wire that's in a magnetic field the wire

is going to move because the magnetic

field produced by the current flow

interacts with the a stationary magnetic

field so in a magneto hydrodynamics

drive if you have a conductive liquid

and we pass some currents through it and

there's a magnetic field going on there

will be a reaction force or imagine that

the liquid is actually forming a wire

and it's getting pushed out of the

magnetic field and then more water or

conductive liquid flows in you might

also know that you can move a stream of

water with an electrostatic field and no

magnets just by charging up a plastic

comb or a piece of PVC pipe and holding

it near a stream of water now it's not

quite fair to call this a pump because

the thing that's actually doing the work

is my hand bringing the plastic pipe

closer to the water stream to qualify as

sort of a real pump it would have to run

continuously by itself and have an

energy source coming in and changing the

pressure and flow of the water so today

I'm going to show you an electro osmotic

pump which I think is a more obscure and

maybe more interesting way to play with

electric fields and water so quickly

we've got two glass cylinders here

they're actually pipettes and the water

column joins into water on this side and

this column joins into water on this

side and when I say side the two sides

are divided by a glass frit filter so

this is basically just blast particles

packed together and then centered

together to make this hard disk which is

porous and then on either side of the

disk there is a stainless steel wire

mesh screen which is connected to a

stainless steel rod and the rod exits

the water

chamber so that I can connect up to it

electrically very simple setup and the

fluid is just pure deionized distilled

water it's as pure as I can get it and

then we've got our high voltage power

supply here and a current meter to

monitor how much current is going

through the circuit

pretty straightforward so let's turn it

on we've got about 200 volts selected

and as soon as I throw the switch keep

your eye on the water levels in the two

columns there will turn on and yeah it's

it's pumping water quite fast actually

we're drawing about three milliamps and

we're running at 200 volts DC and you

can see that it's actually overflowing

the top here now something interesting

happens if I put my finger on the end of

it watch what happens to the current as

you can see here now we're down to 1.6

1.5 millions and you can see on the

graph here the history of what's

happened and if I remove my finger

current starts to increase again let's

see that effect on current again this

time I'm going to change the timescale

here so that it's maybe a little bit

easier to see so we'll go to one second

so that we can see the graph passing

more quickly and I also added more water

to both sides and when I switch on I'm

going to alternately plug and unplug

this and then also add more water to the

other side to try to keep the levels

about the same so switch on here 200

volts you can see it's coming out and

we'll let this thing try to stabilize

and as it's going I'm going to be adding

more water to that side to try to keep

it equal so we've got maybe one point 4

milliamps and if I plug this up it's

going down and if I unplug it it's

heading back again so we're getting a

swing of maybe about half a million

verses plugged flow verses unplugged

flow so it's about 0.9 and if I let this

go pretty obvious changed there so it's

pretty cool that we have a pumping

device let me turn this off pretty cool

that we have a pumping device that moves

water with

an electric field no magnets pure water

that's non conductive or at least as

close to non conductive as water gets

and then also it functions as a flow

sensor so that if we adjust how much

water is allowed to flow through it we

can read that out with the current as

you might have guessed the direction of

the water flow can be controlled by the

electrical polarity so if we do 200

volts in this direction negative on this

side you can see the water column is

rising on the right and if I turn this

off there's a switch on the back of this

power supply that flips the polarity so

now if we turn on the water is pumping

the other way this the right side is

going down the left sides going up one

thing you'll notice is when I switch

this off and there's no electrical field

across here the water is very very

slowly returning back to the equilibrium

point and the reason for that is that

this porous glass filter is really

restricted to flow in fact it holds

water against gravity even you can fill

this little beaker up and water does not

flow through because it's just such a

small hole size just to give you an idea

if what kind of pressures this setup is

capable of producing I've plugged this

side up so that there's no way the

syringe can back out on its own and then

I've connected a pressure gage up not

with a super solid connection here but

it good enough for today's purposes and

we're gonna pump in this direction so

the pressure gage will so positive

pressure here switch on and as we saw

before will notice that the the current

will actually taper off as this thing

compresses the air space that's up here

and eventually it will reach an

equilibrium point similar to having my

finger on the top here so we know when

the current levels off there's no more

flow going through and the pressure

reading will be valid so it's a little

bit above where it was it's maybe about

three-quarters of a PSI

you

now I know what some of you are thinking

what would be what would happen if we

measured the current flowing through

this without the high voltage supply and

then forced some water through it let's

try it so I will disconnect here and

here and connect this up here so now the

high voltage supply is completely

disconnected and we're measuring just

the current and I'm going to change the

range to be a hundred micro amps ok so

the current is drifting a little bit but

it's more or less stable at about seven

point something biker amps and that's

probably due to a slight amount of

electrochemical action in there so I'm

gonna cap this end and then squeeze the

syringe here to force water in one

direction through here and as we can see

there's a pretty big current change and

if I pull it back the other way there's

a change back the other way so this was

sort of one flow if I try to keep it

constant it'll be below this baseline

and water is flowing through the device

now if I switch and go back the other

way we can actually monitor the flow of

water through the device very very

accurately in fact I'm just you can

actually follow the water column here to

see what the pressure is

and the signal that we're reading out is

most likely due to the flow through this

electro osmotic system pretty cool

here's a drawing of what's happening

inside the electro osmotic pump we've

got both water columns here and they're

joined together and then separated at

the bottom with this fretted glass

filter and on either side of the fretted

filter we have our electrodes so the

thing to know here that the real key

that's driving this whole thing is

something weird that happens when we put

water next to glass and this is true for

plain old pure water next to plain old

pure glass regardless of any electric

fields going on or any weird business if

you just put water and glass together

this is what happens the glass is

attracted to the OAH part of h2o and

actually separates the water slightly so

that the H+ is free to move but the O H

is actually stuck to the surface now

normally you don't really notice

anything happening when you're just you

know playing with water and glass or

even do

chemical reaction because this distance

over which this effect is happening is

really short so the surface of the glass

causes this slight separation of the

water but it's really only happening

within a very very narrow distance of

the wall but it does happen and then if

we put an external electronic or

electrical field on here

the fact that we've got these free H

pluses moving means that they are now

affected by this field so if we have

positive here and negative here and the

negative part of water is basically

stuck to the wall that leaves these

positives free to move and they will in

fact be moving toward the right in this

diagram because they're positively

charged and the electrodes are you know

opposites attract basically the system

can run indefinitely because the water

is basically discharged out this side

and then more water flows in and the

glass will cause the separation with the

new water that flows in and the old

water that flows out the two parts

recombine and everything is fine so if

you look at the whole system or at least

the glass water system as a whole

there's no net charge because everything

is balanced it just happens to be that

near the wall there's this charge

separation so as you might have guessed

this happens with more materials than

just glass and water in fact it happens

with most materials well I shouldn't say

most but more than you might think I

know that it also works with plastic

membranes track etched membranes we'll

do it with water you can also use a c2

nitrile instead of water that works just

fine to the things that won't work our

fluids that can't be separated like this

so nonpolar things like oils or

hydrocarbon type liquids and stuff

probably won't work but alcohol would

probably work because it has it's a

polar molecule and you can probably

cause this splitting to happen another

interesting thing is adding something to

the water that will make it more

conductive and I'll put links to all the

papers in the description but at first

you might think this is a bad idea

because ideally if the water was

completely non conductive which it isn't

by the way but let's just

say we had a fluid that was 100% not

conductive that would be great because

we actually don't want any current to

flow between these electrodes as it

turns out though having some amount of

ionizable stuff in your solution

actually helps this process out so in

one of the papers they figured out that

adding ammonium hydroxide to the

solution up to a point increased the

efficiency of the pump there's a lot of

sort of complicated math that they like

to throw in there because it's an

academic paper but it is actually an

interesting optimization problem like

you basically don't want a lot of

current to flow obviously if we dumped

in like a ton of salt and we put our 200

volts across here you know an amp is

going to flow and it's going to be

terrible efficiency most of the power is

going to be going into electrolysis we

don't want a current to flow between

these two electrodes causing a chemical

reaction and splitting up other stuff in

the solution but if there's a very small

amount of conductive stuff either salt

or sodium hydroxide or ammonium

hydroxide or anything in a way that's

good because it makes this layer thicker

the idea is that if you add more ions to

the solution you can make this layer

over which this splitting is happening

thicker and if you have a thicker layer

of charged stuff here if separated stuff

then your pump is more efficient because

it has more to grab on to I should also

point out the flow profile in this small

passageway is very unusual in almost all

cases if you have flow through a pipe

the flow profile is parabolic and the

reason for that is the so if this is

your pipe here the stuff in contact with

the wall the fluid in contact with the

wall can't move because it's in physical

contact and the stuff in the middle is

farthest away from the wall so it has

the highest speed so in pretty much all

em in our pipe flow situations you've

got this parabolic flow profile but

something very weird happens with this

electro osmotic flow the stuff at the

wall still can't move because it's in

contact with the wall however the pump

applies the most force to these charged

particle

the closer they are to the wall because

there's more of this charge separation

going on so you end up with this really

weird profile that looks kind of like

this so you have zero velocity at the

wall but then it goes to maximum

velocity but then at the center there's

the least amount of force applied to the

water because it's far away and so you

end up with something like this which is

pretty bizarre I think it's the only

case that you would get such a thing the

system is also very tunable so by

changing the the thickness of this

porous block the diameter of the porous

block the size of the pores the voltage

and the spacing the electrodes you can

really custom tailor this pump to be

almost anything you want so in this case

the poorest part has a diameter of about

30 and the thickness is about 4.5

millimeters and we were getting flow

rates on the order of 20 milliliters per

minute at about 200 volts at 3 milliamps

and you saw the pressures could be as

high as about Oh 3 psi and maybe about

600 volts and so this is pretty well in

line with with the academic literature I

should also point out that the

electrolysis is the completely unrelated

sort of side reaction from the

perspective of all this electro osmotic

pumping if we had a fluid that just

didn't happen it just didn't do

electrolysis that'd be great there is a

certain amount of current that's flowing

between here and the the energy is going

into splitting up those molecules so

electrolysis means we're splitting water

into hydrogen and oxygen and that's

actually consuming most of the energy in

this system the thermodynamic efficiency

of this electro osmotic pump is actually

really terrible it's on the order of

about 0.1 percent and so 99.9 percent of

the energy is going into splitting the

water even though it's still a

relatively small amount of energy and

it's only that other tiny bit that's

going into moving the fluid so compared

to mechanical pumps you know you're not

going to beat their efficiency the

reason that this electro osmotic pumping

is

cool is because you can scale it to be

anything from you know microns big up to

meters big and it will accommodate all

kinds of different flow and pressure

situations this terrible efficiency was

shown in the experiments tonight because

when we were pumping water through here

forcefully and measuring the electrical

current we saw the numbers were very low

like on the order of 5 micro amps but

when we're putting electrical current in

an expecting flow out we had to put in

something like three milliamps and so

it's showing you sort of the order of

magnitude of efficiency there another

question is why is this called

electroosmosis I don't think this is

actually a great name for this

phenomenon but it sort of makes sense I

recall what osmosis is if you've got

this new channel filled with some mild

salt water and a membrane at the bottom

through which the salt cannot pass but

water can and then you add more salt to

one side what will happen is the water

will actually be pumped across the

membrane so that the concentrations will

attempt to be equalized by this process

of osmosis and it's actually very subtle

how this works right it's not like the

universe knows that there's a there is

an imbalance and it's trying to correct

it what's happening is there's random

collisions happening with this membrane

down here and if a water molecule

collides with it there's a chance that

will go through but if a salt molecule

collides with it there's no chance that

will go through and if you run the

simulation it just happens to be that

the water will eventually move across

such that it equalizes out all these

random chances it takes a little while

to wrap your brain around it if you

haven't thought about this but it's kind

of cool how random chance works like

basically if you've got a ton of salt

over here the chance that it slams into

the membrane is high because there's so

much salt there but it's never going to

make it through the membrane so it stays

on that side

hence water will more likely flow into

that area of higher concentration so

you've seen things like reverse osmosis

filters which apply a pressure gradient

and force the clean water basically

through the filter I mean one way of

thinking of it is you've got this filter

that's resistant to flow and you're

basically forcing water through

but another way to think of it is that

dirty water would normally just sort of

equalize itself out and by applying a

pressure you're shifting the gradient of

this osmotic balance and so

electroosmosis means we're using an

electric field to apply this bias like

instead of applying pressure and using

that to separate out some sort of a

solute in there we're using the electric

field to separate out these charged

particles and as we saw it's basically

these these positively charged things

that are induced that way by the

chemical reaction with the wall one

thing you might be wondering about is

this fretted glass filter is not really

a series of tubes it's like a whole

bunch of you know random spaced granules

of glass all sort of jammed together but

keep in mind the electric field is

always very uniform it's incredibly

uniform so even if the passageway is

very tortuous the flow profile like the

force or the the the force on these

charged particles is always going in the

right direction so even if you have a

really tortuous path it ends up always

flowing through in the right way your

efficiency would probably be better if

they were oriented all the same but it

won't ever flow backwards or anything it

always pushes in the right direction the

filter that I'm using has particle size

between four and five and a half micron

let's take this thing apart and I'll

make comments on how I built this as we

go so the columns are just regular old

glass pipettes and I drilled a hole in

here and just shoved an o-ring in and

then put the pipette in and that made a

pretty nice seal with that and then

there's a large clamp just holding it

all together which I'll undo and this

whole thing will probably spring apart

hopefully carefully okay and we can see

one end here and all the channels are

just connected together and then to keep

the water from leaking out with the

electrode pass through I have a piece of

silicon tubing just shoved in there

basically is kind of like an o-ring seal

the stainless-steel rod itself is just

welding rod and I kind of really crudely

spot-welded it to this stainless steel

mesh which I cut out with scissors and

here's the glass frit membrane and then

I've also just got lure connections on

to here so I can quickly plug a syringe

in and pump water in or out of each side

to make these blocks I my preferred

method is to use the fly cutter on the

mill and then quickly sand it with

thousand grit round the corners apply

around over to the edges and then just a

quick pass with white Rouge and that

actually leaves almost a really nice

optical finish not quite museum quality

but quite nice for what we're doing oh

and then I also have a piece of silicone

just to seal to the glass okay well I

hope you found that interesting see you

next time bye--make money online top websites to earn money, online typing jobs for students to earn money, earn skrill money online, earn skrill money, best way to earn money from home, make instant money online absolutely free, trusted online money making sites, online income site, best online earning, money online, earn money from home, earn dollars online, earn money online, earn money online 2019, earn money online by typing pages, earn money online daily, online work at home and earn money, online earning, earn money online free, online money earning sites, earn real money online, e commerce ideas to make money, easiest way to earn money online,