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Any clinical results yet?
It seems that most cryoprobes work with a tip temperature of -40C or below: can you achieve comparable or at least useful results with a domestic freezer at -5C?
Wikipedia - Refrigerator - FreezerMost household freezers maintain temperatures from −23 to −18 °C (−9 to 0 °F),
If so, you are on to a winner.
Have you considered adding a salt water/ice bath to the handle?
The freezer-baton has a feature to counter-act the inevitable tendency of a solid tool tip to be warmed by the patient's skin and the environment - an encapsulated water / anti-freeze solution which draws warmth away from the tool tip, effectively when mixed by effortlessly and intermittently inverting the freezer-baton, glugging an air-bubble within the solution up and down within the encapsulated volume.
The saltwater/ice solution is cheap, and can cause freezing point depression that may actually be further than just using antifreeze, as well as keeping it colder for longer as the ice melts.
I don't run my freezer at -36°C
I think salt will actually make ice colder. So, you can start with ice at 0°C, but by adding salt, you actually can push the temperature down to about -20°C (different solutions will also work).However, the latent heat of fusion of ice is also about 80 calories. So, as it melts, it will stay colder about 80 times as long as just water or antifreeze.
There is, of course, a lot to say about the simplicity of a sealed system.
So, if you have a large enough of a heat sink, and a cold enough freezer, you may not also need the ice and salt.
Liquid nitrogen cryo-freezing is quick.
I'm not sure how long your device needs to be applied to the skin. I suppose at least long enough that the wart or lesion completely freezes through, but that may still be fairly quick.
" it seems that prospective others have chosen not to collaborate with me."there may be reasons for that.
"If salt water was a useful antifreeze they'd use it in car-engine cooling systems - they don't because water / ethylene glycol mixtures remain liquid at far lower temperatures."No, they don't (usually) use salt because it rusts everything to hell.
"Water ice melts at 0C which is far too warm a temperature to use for cryosurgery. So melting/freezing ice is out. Sorry but salt water & ice is simply not a useful suggestion and frankly I am beginning to tire of explaining this to you"Pure ice melts at 0C but salt and ice melts at about -18CThat's as cold as a typical domestic freezer, so, if your product works with a freezer cooling it, then it would work with ice and salt cooling it.
The important point is that the ice salt mixture has a much greater cooling capacity.
So, before you "tire" of explaining things away, perhaps you might liek to try understanding them first.
You are claiming that there is some benefit that applies at -18 to -23C which is not available at -21.12C.Do you have a basis for that claim?Do you realise that it doesn't make sense because -21.12 is in the range -18 to -23?"In a domestic freezer at -23C, sodium chloride solution would be frozen solid and would be useless as a coolant."And in my freezer (the last time I checked) at -18C it would be just fine.
"No, salt-water ice has a much poorer cooling capacity because as ice is a solid it cannot circulate and transfer heat anywhere nearly as quickly as can a liquid."Still wrong for the same two reasons as before.You can pass salt water over ice and cool that saltwater to about -20C. - it's still a liquid.
And you have ignored the heat capacity effect.The latent heat of fusion of ice is large.which leads me to think this assertion "I do understand these things,"Is still wrong.
Well here's one reason that this scientist and entrepreneur won't collaborate with Mr Dow: he insists on publishing rather than patenting his inventions and trade secrets. This might attract a desperate academic who needs publicity, but it won't interest anyone with money, machinery and manpower to invest in developing and marketing a product. If it was common knowledge that this gizmo actually works, some philanthropist might find a workshop that could get the device out into clinical use, but in the absence of clinical trial data there's nothing of interest to a manufacturer, and in the absence of patent protection there's no point in a laboratory running a trial to MHRA or FDA standards (and you can't even donate, never mind sell, the product if you don't) if the intellectual property is going to be given away.The only hope is to convince a charity or a government department that removing benign warts and tags is of such enormous public benefit, and so prohibitively expensive or ineffective when done by conventional means, that the development of this gadget should be supported pro bon publico. But I suspect the public purse has more obvious priorities. On the face of it, this is not the new pennicillin.
Alan,Good point, but I'm not sure this product could be patented; I don't think it's novel enough.I think "using a cold thingy" to freeze tissues is "obvious" in the sense of the word used in patent legislation.So I think the real killer here is that this product doesn't offer enough value to healthcare providers: as you say, it's not "the new penicillin".
On the other hand, a freezer-baton is not a sufficiently powerful and flexible tool to compete with the type of high-tech, high-cost cryo-surgery probes which a modern hospital can afford.So I would not claim that my design is a breakthrough in medical science and engineering that will sweep all competition aside.Rather my freezer-baton design is more the kind of design which one might have expected to have seen bodged together for a Scrapheap Challenge or a student project maybe!
Quote from: CliffordK on 20/05/2014 19:50:05I'm not sure how long your device needs to be applied to the skin. I suppose at least long enough that the wart or lesion completely freezes through, but that may still be fairly quick.For one spot on the skin, maybe 30 seconds or so, as far as I remember. It has been a while since I tried the first prototype I made on myself.
You cannot seem to get your head around the requirement to design such a tool which works with everyone's freezers, including those which are run at colder than -21.12C.Imagine the disappointment of someone who gets a freezer-baton only to discover - oh sorry, this tool will not work with your freezer running at -22C because the idiots who designed it had used salt water as a coolant!
I don't know if there is a huge market for wart removal, but there is for age spots, and if it works on that, he might have something pretty marketable, since most people do not have a container of liquid nitrogen or a laser at home.