Naked Science Forum
Non Life Sciences => Technology => Topic started by: Peter Dow on 19/05/2014 14:36:38
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I'm describing here my design and construction project of a simple tool for basic cryosurgery - limited to freezing superficial skin lesions such as verrucas and warts etc - and possibly other applications where freezing temperature needs to be applied to only a small part of a larger mass.
My tool which I have named the "FREEZERBATON" or "Freezer-baton" employs a preparatory step of temporarily cooling parts of the disassembled freezer-baton in a domestic food-freezer before a simple assembly prior to applying the tool tip to the spot that needs freezing.
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.
When the freezer-baton has inevitably warmed through to the core and therefore has become ineffective for freezing anything, it can be disassembled and returned to the domestic food-freezer for re-cooling for later re-use.
A freezer-baton like this can be manufactured from off-the-shelf parts available from a DIY or plumbing supplies shop.
The following photographs of my freezer-baton should provide enough familiar information for a skilled plumber or anyone with a DIY aptitude and experience to make something similar.
Freezer-baton by Peter Dow
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fscot.tk%2Fforum%2Fmedia%2Ffreezerbatonpeterdow_A_800.jpg&hash=c3ca12977f5b74b2c4d3bf814787ba7e)
Alternative image link http://s25.postimg.org/rvxxegutr/freezerbatonpeterdow_A_800.jpg
Freezer-baton secured to go with carry-case bungee cords. Weight 1068 g
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fscot.tk%2Fforum%2Fmedia%2Ffreezerbatonpeterdow_B_800.jpg&hash=34664fb51f7004a55539e590c2146b7c)
Alternative image link http://s25.postimg.org/d19c0al8v/freezerbatonpeterdow_B_800.jpg
Unhooking the bungee cords from one end of the freezer-baton carry-case allows the tool to slide out of the stand.
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fscot.tk%2Fforum%2Fmedia%2Ffreezerbatonpeterdow_C_800.jpg&hash=8bfe95208221511b72a8defd0cb0f470)
Alternative image link http://s25.postimg.org/8tejrjjtb/freezerbatonpeterdow_C_800.jpg
Freezer-baton unboxed - Stand (258 g) & Tool (810 g) (showing tool end-cap, grip & tip)
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fscot.tk%2Fforum%2Fmedia%2Ffreezerbatonpeterdow_D_800.jpg&hash=ec687715bc1db266f755cecfd85ba411)
Alternative image link http://s25.postimg.org/j4qwk7bin/freezerbatonpeterdow_D_800.jpg
Tool disassembles for quicker cooling. 1. End-cap pulls off, 2. Nut unscrews, 3. Grip pulls off. Showing tool end-grip revealed when the end-cap is pulled off
Compare and contrast the freezer-baton with established cryosurgery tools
Even simpler and lower-cost for the occasion use are the verruca & wart remover freezing aerosol kits one can buy from the chemist, which use dimethyl-ether - propane.
Wikipedia: Cryosurgery - Dimethyl ether - propane (http://en.wikipedia.org/wiki/Cryosurgery#Dimethyl_ether_.E2.80.93_propane)
However those kits have a strictly limited number of applications before the aerosol runs out. Also, a cold liquid which might drip or run is harder to control than a cold solid.
The freezer-baton never runs out of chemicals and my food freezer is on all the time anyway so there's little or no additional running costs of cooling a freezer-baton when I need to.
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!
I had made my first prototype of this cryosurgery tool minus the plastic parts and had insulated it with only pipe insulating foam a few years ago but although it seemed to work OK, because it wasn't doing anything new that other existing tools couldn't do just as well or better, I didn't see any great urgency in publishing anything about it at the time.
Now that I've completed this second tool (because I lost the first tool) and this time I've also designed and made the plastic insulation, grip and stand, I think it may be worth publishing this brief project report?
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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? If so, you are on to a winner.
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Thank you for being the first person on the internet to ask me a question about my freezer-baton.
Any clinical results yet?
No.
I've tested the freezer-baton on myself but that's all.
I'm an independent scientist at age 53 not by choice particularly but because it seems that prospective others have chosen not to collaborate with me.
But yes, in principle, of course I am supportive of the notion of clinical trials of my freezer-baton design should anyone else wish to pursue such.
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?
A good domestic freezer should cool the food down to -18C or below.
Wikipedia - Refrigerator - Freezer (http://en.wikipedia.org/wiki/Refrigerator#Freezer)
Most household freezers maintain temperatures from −23 to −18 °C (−9 to 0 °F),
So the tip temperature of the freezer-baton may operate at those sorts of temperatures, though the precise temperature is likely to fluctuate with a gradual warming trend in operation.
I've already conceded that most existing cryoprobes are more powerful and flexible than the freezer-baton in my "compare and contrast" section in my OP.
If so, you are on to a winner.
In a cost / performance competition with existing cryoprobe designs, the freezer-baton design loses on performance but potentially could win on cost because the running costs would be very low.
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Have you considered adding a salt water/ice bath to the handle?
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Have you considered adding a salt water/ice bath to the handle?
No.
Have you actually read and considered this part of my OP?
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 "encapsulated volume" referred to is within the copper pipe which runs the full length of the tool from tip to end, including the "handle" as you put it.
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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.
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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.
The freezing point of a water / ethylene glycol (http://en.wikipedia.org/wiki/Ethylene_glycol#Antifreeze) (ethanediol) antifreeze mixture is far colder than simply adding salt to water.
For example, the 50% water / 50% ethylene glycol mixture depresses the freezing point to -36C which is plenty low enough for this application.
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.
Thank you for your suggestion but no thanks.
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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.
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I don't run my freezer at -36°C
Therefore your domestic freezer would not freeze my selected 50% water / 50% ethylene glycol mixture. Therefore my tool would work with your freezer same as it would work in everyone else's freezer which cool only down to typically around -18C to -23C.
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.
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.
There is, of course, a lot to say about the simplicity of a sealed system.
The simplicity and low operating cost of the freezer-baton are indeed its main advantages.
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.
No Clifford sorry. Ice and salt is a "no, no" for this application. Not only don't you "need" ice. You don't want ice in the encapsulated volume as it would obstruct the flow of coolant which is required to distribute the absorbed heat away from the warming tool tip into the core of the tool.
Liquid nitrogen cryo-freezing is quick.
Yes it is much colder.
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.
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.
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" 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 -18C
That'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.
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" it seems that prospective others have chosen not to collaborate with me."
there may be reasons for that.
The inquisition didn't need a "reason" to burn Giordano Bruno at the stake but that certainly stopped his future collaborations with other scientists.
http://en.wikipedia.org/wiki/Giordano_Bruno
Neither did the United Kingdom's authorities need a reason to persecute the computer scientist Alan Turing, but they drove him to suicide anyway despite his unsurpassed contribution to defeating the Nazis, again stopping his future collaborations with other scientists.
http://en.wikipedia.org/wiki/Alan_Turing
The powers that be have never needed "reasons" to persecute any excellent scientist, wreck his or her life and / or career and prevent or deter prospective others from future collaborations with that scientist. Persecuting scientists is not an act of reason but an act of prejudice and malice.
"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.
That's an additional reason for not using salt - water solutions for cooling. Your additional reason doesn't invalidate my stated reason.
"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 -18C
That'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.
For sodium chloride solutions (http://en.wikipedia.org/wiki/Sodium_chloride#Aqueous_solutions), "the freezing point is −21.12 °C (−6.02 °F) for 23.31 wt% of salt".
But I've already quoted a source which states that typical temperatures for domestic freezers are in the range -18C to -23C.
In a domestic freezer at -23C, sodium chloride solution would be frozen solid and would be useless as a coolant.
The important point is that the ice salt mixture has a much greater cooling capacity.
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.
So, before you "tire" of explaining things away, perhaps you might liek to try understanding them first.
I do understand these things, thanks all the same.
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http://rationalwiki.org/wiki/Galileo_gambit (http://rationalwiki.org/wiki/Galileo_gambit)
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.
Just like you were wrong here
http://www.thenakedscientists.com/forum/index.php?topic=49201.msg422756#msg422756
and, incidentally, you still haven't answered my question at the end of that thread.
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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.
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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".
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With warts being pretty benign, my guess is that the approval process for an "alternative therapy" for simple warts could be streamlined, although initially it probably wouldn't be advised for plantar, genital, or facial warts. However, a home remedy may be a benefit on hard to kill warts.
I can't imagine it would be any worse than putting on salicylic acid on a daily basis for a month or so.
Bringing the device from simple design to manufacturing should be quick, although undoubtedly one would choose injected molded plastic, and perhaps some foam on the handle rather than PVC pipe.
If you are anticipating this to be home-built, then actual specs & assembly instructions would be helpful.
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I just checked my freezer, about -5°C... hardly much colder than using a simple ice cube thus the benefit of salt and ice, just like using an old fashioned ice cream maker, using freshwater ice, of course. But it is your device, if you are posting for a critical analysis. And... the freezer is cold enough for me.
As far as the copper tube. If it is physically attached to the copper tip, then it will act as a heat sink. Otherwise, during active use, the copper pipe will likely be of minimal benefit. If exposed, it will allow more rapid cooling, but even PVC will allow your device to get cold if left in the freezer overnight.
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http://rationalwiki.org/wiki/Galileo_gambit (http://rationalwiki.org/wiki/Galileo_gambit)
Bruno, Galileo, Turing and myself, as real scientists, never had any problem with mere "serious criticism" which in an open and non-threatening debate is like water off a duck's back to real scientists whereas to the powers that be, "serious criticism" in which said powers' authority to impose doctrine is challenged is so loathed by the powers that be that to save face they are driven to use the power of state violence to impose its persecution of the "serious criticism" they cannot tolerate.
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.
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!
"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.
But ice in a coolant pipe can block the flow of coolant, so that's why salt water is not suitable as a coolant where freezing is an issue.
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.
The latent heat capacity of ice is irrelevant because ice cannot be used because it would block the coolant pipes and prevent the flow of coolant.
Again sorry but I find replying to your points has become tiresome.
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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.
Fair enough Alan. Thanks for your input to this discussion anyway.
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".
I wouldn't waste any effort disputing that the freezer-baton is "not novel enough to be patented".
I was very clear and modest about expectations in my OP.
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!
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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.
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.
To quantify the freezing ability of the freezer-baton, I've experimented and the result was that the freezer-baton was able to freeze an average of 0.2 grams of water/minute over the 13 minutes running time of the experiment.
Initially, the freezing rate was 0.3 g/min but possibly because ice was building up on the tool tip, the freezing rate dropped so that after the 13 minutes the freezing rate had dropped towards 0.1 g/min.
That's with inverting the tool every 30 seconds to glug the air bubble / coolant up and down the copper pipe to mix the coolant.
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But the object of cryosurgery, like any other topical treatment, is to kill the target without damaging the surrounding tissue, so you need to establish the required rate of cooling to do so, then demonstrate that your gizmo can achieve it even when it's been cooled in Clifford's freezer. Thanks to the conductivity of skin, and capillary blood flow, it's entirely possible that a probe held at -5 deg C for long enough would induce a large area of frostbite (thence gangrene and amputation) without actually disrupting a wart, which is why commercial cryoprobes tend to run at very low constant temperatures or put the refrigerant in direct contact with the target.
Obviously a real scientist like Bruno, Galileo, Turing or Dow will have done the calculation and verified it by experiment before going public or seeking a collaborator. Do please let us see the results.
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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!
So, you accept that you have failed.
Your device won't work in Clifford's fridge at -5.
But if you make ice in his fridge and pump salt water over it, the temperature will drop to about 20 below. That's good enough (or if it isn't then your idea is doomed anyway).
Also, for a given weight , ice will provide more cooling capacity. It will do this no matter how many times you ignore the fact.
"But ice in a coolant pipe can block the flow of coolant, so that's why salt water is not suitable as a coolant where freezing is an issue."
Well, don't put it there then. Did you think that was a valid point?
It seems you are still no Galileo.
And you still haven't answered my other question- the one I asked in the other thread.
Here's a copy.
BTW, is this you?http://www.dailyrecord.co.uk/news/uk-world-news/meet-the-lonely-heart-from-hell-1079428 (http://www.dailyrecord.co.uk/news/uk-world-news/meet-the-lonely-heart-from-hell-1079428)
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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.
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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.
Quick way to find out: take a fresh ice cube from your freezer and put it on your granny's hand.