Glass on Glass. How do you seperate?

Perhaps there could be some pre-drilled holes in the metal so a gas or liquid could be forced in to cause separation. I think the glass would be easier to remove from a metal surface because bonds would not be as strong between dissimilar metals. Again, not really my field just speculation.

Hi Kris,

The metal pieces have hole(s) in them so you can inject air pressure to separate the glass from the metal. There wouldn't be ionic bonding like you have with the glass on glass.

Seems like it might work.

John

Thanks for clarification johnhohn. I was loosing myself because a 'frame' had been mentioned before (with cross bracing like an empty window frame , but the suggested use was more for handling in general)- a machined block with air injection holes is a similar approach.

Cheers , Kris

No gurue here, but I love to try to help. One thought is....the glasiers suction cup. Although your application is a little smaller than theirs, a small suction cup on the top piece with a little twist is one thought. Another might be a lite jet of air from your tipical air nossle blown just between the two layers. Both ideas will need to be approched with care or delicasy!

I hope these ideas can help.

This sometimes works on larger sheets of glass but I'm not sure how well it will work here. Stand them on end with tape applied to both surfaces to act as handles. Use a highly carbonated warm club or selzter soda. (lots of fizz). Pour the liquid over the upright pieces totally covering them. While the carbonation is still active try to gently slide them apart. Hopefully a capillary action will allow the gas to get between the sheets and break the bond. Good Luck!!

never pry. The thin pieces must be slid sideways

You need to get something with a smaller molecule size than the glass molecules between the two pieces of glass. Alcohol molecules are too large

Try a to blow Helium at the edge of the small glass and slide the piece off

Hi,

if the bond is not too strong (chemically) it helps to induce a little bending on one edge of the thin plate and then just wait for minutes to hours to let the water (with surfactant) go in. As the gap is down to 0.4nanometer this will require considerable time.

Viscous flow rate is proportional to the cube of gap width.

So if o.1 mm gap separates under water in 1 second, this will require up to 15x10¹⁵ sec.

(with the same force), so if you do not have additional water pumped in it is unlikely to get the pieces apart.

I assume that it is necessary to pump some water into the gap between the plates:

seal a plastic or metallic tube of the smallest diameter you can get to one side (insuline syringes may be good) seal this side totally with epoxi or other seal , not the three other sides, then pressurise the tube to allow some very small amount of water to enter. Allow for one day to judge, maybe you see some color fringes where loosening starts.

Try first with a non needed part to establish pessure level and gluing integrity.

Good luck

RHABE

Any help??

We all tried offering so many ways.But------------.

Before you give up --one last suggestion-- this time Electromagnetic.

*1 Place a work coil of an Induction Tool brazing set just above the thin glass. Go on increasing timesd and intensites--and feel with bare finger if ther is an increase in temperature. While feeling keep pushing/prying in a thin knife edge.

Once the knife edge enters -rest as per the other 100 suggestions you already received.

*2 If Work Coil Induction(450KHz?) won't budge it--

Bring in Microwave E field between both glasses together. Get somebody rig up your kitchen microwave to radiate between these Stuck pair at the homemade Split Waveguide End placed just on the Stuck Pair.

This time heating up will be for sure.And most likely the bond will too.

After that-we all Celebrate!!!!!

Microwave oven heat only because they make water molecules spin. Try putting a cup of oil in your microwave... I doesn't even get warm.

Glass will-Some glasses more. Fused Quartz -marked 'Oven-safe' won't heat much.

Microwave oven heat only because they make water molecules spin

I thought they oscillated because the microwaves were attuned to resonant frequency of Hydrogen. I need to ra-align my beam for your head vermin.

OK, here is my last shot... On a thread I started, I'm asking about the best materials to use with DI water (I have my reasons). Anyway, I've been learning that really good DI water is highly reactive and will attack all types of stuff. I'm thinking that if DI water got you into this mess it might be able to get you out.

Try soaking the specimen in really pure DI water. Perhaps, give it a day or two. Then, without contaminating the DI water, try prying the pieces apart while still submerged. I'm thinking that the DI water may be able to penetrate and dissolve the original bonds created by same.

What the heck! I'm spent!

The Prince of Wales (later King Edward VII) once had a quarrel with his mistress, Lillie Langtry. "I've spent enough on you to buy a battleship," the prince complained. "And you've spent enough in me," Lillie retorted, "to float one!"

How about differential cooling of the 2 pieces ( I don't remember if that's been said ).

"...Lillie retorted, "to float one!"..."

I tried to visualise. To no avail. Too much porn these days.

Blame vermin - he started it ! Even if he didn't , blame him anyway - It's fun.

I was merely being historically and linguistically helpful.

I've only just got round to this thread. I've used this sort of bonding for attaching thin films - and they only ever separated when the surfaces were not as clean as they should have been (that would have been quite soon after assembly as well. So you may have to consider other methods to remove the carrier).

However:

Laser ablation of the interface (if possible) and ultra-rapid cooling suggested by others sound to be the best bets so far. However, regarding the cooling, I fear it will be difficult to obtain suitable uniformity or contact using dry ice. Even though you won't get it as cold, I would try a low freezing solution (antifreeze, salt?), which will give better contact, even though it is nowhere near as cold. You could work your way downwards in temperature until the materials either crack or release. You are probably as well equipped as I to find other lower temperature fluids**

Another high-tech possibility would be focussed acoustic waves, but it only has the slightest chance of separating the materials if there is an interlayer (otherwise, you'll get ultrasonic welding...)

Again, in the unlikely event that the surfaces are not truly joined, you might get somewhere using a cavitating acoustic cleaner (only because it might help the fluid penetrate)

Failing all these, can you protect the front surface and lap/etch the unwanted carrier away*** (doubtless Murphy says the the sample is both softer and more soluble than the carrier)?

Good luck - and keep us all posted.

Fyz

**The only ones I've personally used are
Mercury to stabilise -40 in the past - but suspect it wouldn't be accessible these days, and I'm not certain how well it flows near its freezing point.
Liquid nitrogen (77K) is too extreme, but it's reasonably readily available nearly anywhere that does serious vacuum work, and worth a try if other not-quite-as-cold fluids don't crack the sample (take advice and precautions).
(Also liquid Helium - but that would be really silly)
***Early pressure sensor films of similar and lesser thickness were fabricated using timed etching - it should work if the carrier surfaces are parallel enough.

I don't see how cooling on it's own will find a solution . Too fast (as in dry-ice) and the glass will crack , too slow and the cooling will spread across the boundary of the two pieces and differential shrinkage will be absent (so the two pieces will not separate by shear) .

Acoustic waves - do you think an interlayer is effectively absent because of the atomic level bonding that seems to be the suggested situation. I think there is still a boundary plane (albeit unclearly defined). It sounds horribly like a brute physical force approach is required - all or nothing.

If we have a "proper" bond as I fear, I'm afraid its either brute force separation or etching or lapping away the substrate. Cooling would be a relatively controllable and directed version of brute force:

The way that cooling might work is if we have a combination of factors::
a) the adhesive forces are still appreciably lower than the bulk forces, and
b) we can cool so rapidly that the wanted thin material curls away from the substrate as well as applying sheer forces, and
c) the wanted sample is still essentially free from microcracks (the usual source of early breakage in glass, and extraordinarily difficult to avoid). It is relatively well known that glass fibres can be stretched a remarkable amount if they are free from such cracks, and the same mechanisms apply to films.
N.B. that breakage does not only depend on the applied stress, but there is a minimum energy for crack initiation. So thin films will accept more distortion than thicker materials. 0.002" is already in the region where this makes a noticeable difference - though the effect only becomes dominant in the micron region.

Unfortunately, acoustics are likely to accelerate the bonding process - unless (possibly even if) there is considerably more than a monolayer in the interface. This is because they will alternately provide compression (even if you can arrange a sheer wave in the first instance...)

The symptoms are similar to what I have seen with self-bonding. Normally, this requires a remarkable degree of flatness and high pressure - but thin materials** will conform closely "under their own steam". A typical method is to clean the surfaces, chemically treat them to become hydrophilic, dry them as well as practical, and place them together, The residual monolayer of water (extremely hard to remove) will provide very strong initial adhesion (remember the two pennies stuck together with a meniscus? This will be a much thinner layer and so will generate massively more force). Over time, the water layer will diffuse into the glass (we are talking Angstroms here, so that's not a long time at all), and a covalent glass-to-glass bond will remain.

Thicker materials require more force - if you look up "Anodic Bonding" or "Mallory Bonding", I expect you will find chapter and verse of the physical processes (specifically for glasses) from people who specialise in this area.

**For example, the effect has been used by semiconductor manufacturers to place ultra-thin low-thermally conductive semiconductor layers onto high-thermally conductive substrates. Separation was normally by depositing the wanted layer over a soluble release layer and selectively etching the thin layer from its original substrate. Thickness here is typically in the micron range

Regards

Fyz

P.S. Remarkable technology, this genetic engineering. Not only can squirrels now remember where they placed their caches of nuts, but they also confuse the cats by bouncing vertically.

Hi Fyz ,

I think we are essentially having the same doubts about the viability of cooling and other methods . You are just a little bit (!) more in the know and informative than me. It will be very interesting to hear the outcome of all this. Not just on these test specimens , but also problem avoidance strategies that the maker might use (even though they'll probably keep it secret). I suspect the only present solution is 'hit-and-miss' (sorry , I couldn't resist. OMG stop Kris !) approach.

Cheers , Kris