Ultrasonic baby cleaning

Ultrasonic cleaners work by sending high frequency sound waves through a liquid in some sort of basin. The sound waves cause cavitation bubbles to form on anything you put in the basin, and those bubbles mechanically dislodge dirt from all surfaces of the object - even deep inside nooks and crannies. Ultrasonic cleaners are thus great for cleaning eyeglasses, jewellery, pocket-knives; anything you can immerse in whatever solvent you choose to use.

For household ultrasonic cleaners (as opposed to the huge industrial ones that're used to clean things like engine blocks), that solvent is usually tapwater with a drop or three of dishwashing liquid. Plain water without detergent works pretty well, too.

If the solvent in an ultrasonic cleaner isn't irritating to the skin, you can put your hand in there while the cleaner's running. I wouldn't try that with a zillion watt industrial cleaner, but doing it with a domestic unit just gives you a freaky tingly sensation. If you left your hand there all day you might well end up as a footnote in a medical journal, but a few minutes is perfectly harmless.

I used to have one of the glasses-sized cleaners you can get for not much from any electronics store. Now I've upgraded to a bigger 2.8 litre one that doesn't seem to have much more actual power, but which does feature a nice half-hour clockwork timer, instead of the typical three minute timer of the cheap units. It also makes a pleasing old-microwave-oven "ding!" when its timer runs out.

Anyway, the fact that you can dangle your hand in one of these low powered cleaners when its filled with straight water and suffer no harm occurred to me when some friends were visiting us. They had just observed that they were having trouble cleaning under their baby's tiny little fingernails.

I think you can see where this is going.

Doubtful baby

It worked perfectly. Young Thomas, who does not yet have any strong opinions about the actual purpose of his hands, exhibited no more than his usual level of puzzlement when his mum dipped one of his hands, then the other, in the running cleaner for a minute or two. And his fingernail gunk floated beautifully away.

Your mileage may, of course, vary. If you try this and your baby/child/husband screams the house down, vomits on you or bursts into flames, don't come complaining to me. Complete immersion of the baby is also not recommended, no matter how severe his cradle cap happens to be.

But it sure worked a treat on Thomas.

Suggestions for possible pediatric applications of my 2500PSI pressure washer will be received with interest.

UPDATE: It's been a couple of years now, and Thomas, and both of his hands, remain in working order.

Thomas, the experimental subject

Posted in Hacks. 16 Comments »

16 Responses to “Ultrasonic baby cleaning”

  1. crasster Says:

    I must get my son one of these! Keep up the good work, Dan. Good to see a fellow Antipodean (although on the good side of the Tasman) keeping the blogosphere echoing with Vegemite-fuelled voices.

  2. Devar Says:

    I can't help but think that this kind of vigrorous baby cleaning is part of the reason why some people grow up with absolutely no immunities against bugs and bacteria, and develop conditions such as asthma, because they've had no chance to develop such immunities by living in air scrubbed bubbles with mothers that absolutely-must-remove-every-atom-of-foreign-elements from beneath fingernails lest the baby suck on them.

  3. Phage Says:

    When I started reading this I had a mental image of a small child propped at the focal point of an large dish. Reality is so prosaic sometimes.

  4. Ozem65 Says:

    Dan - having introduced ultrasonic Cleaning into a manufacturing environment - Many years ago- Small bath with a valve oscillator :} - I feel I must comment on immersing hand joints into even a low power bath.

    I just bought one of the little cheapies - 50 watt output and quite effective.

    Now - take a look at http://www.soniclean.com.au/FAQ.html#hands #6 question in the FAQ by Soniclean.

    Next take a look at http://www.soniclean.com.au/ulc/foiltest.html
    I tried this test in my 50 watt cheapie and I was pleasantly impressed to see the dimpling as shown on the site - probably not as pronounced but I was also impressed to see a number of holes in the foil.

    Simply put - NO WAY would I put a child's hand into this kind of cavitating sound energy field and I would not publicise the action as you have due to the apparent risk of joint tissue damage in the short and long term - please do remember that the bones are still growing and there is a disk of high growth activity in EACH bone in a child's hand - not something that should be subject to disruptive ultrasonic sound levels.

    Ozzie (A long term fan of your column!!)

  5. Daniel Rutter Says:

    The smallest cleaner Sonicare sell is a sixty watt unit, and their products go up to 650W. My cleaner has an alleged 50 watt rating, and it may or may not actually put that much energy into the water. As I said, woe betide him who puts his hand in a big industrial cleaner, even if it's only got water in it.

    Anyhoo, if you are a walking skeleton then no, it's probably not a good idea to put your bare bones into even a low powered cleaner, though I presume you're animated by magic and so will probably be OK even then. Although I suppose it'd be just your luck if you'd been reanimated by an absent-minded necromancer who forgot to cure your arthritis.

    Normal humans have soft flesh over their bones - a bit of it, even on the hands - and that flesh soaks up ultrasonic energy very quickly. That's why you can attenuate high pitched sounds so effectively by putting your fingers in your ears. I see no reason to believe that enough energy to do damage will make it as far as the bones of even a very small hand, when there's only a few tens of watts being put into the litre or so of liquid in the first place.

    Ultrasonic cleaners are also like microwave ovens, in that they more or less distribute their energy through everything in the cleaner, so the more water and/or objects you put in the cleaner, the smaller will be the share of the cavitation energy that each object/unit volume of water receives. We probably could have stung Thomas pretty good if we stuck just his hand in there with a shallow puddle of water. But with a litre or so of water and Mum's hand holding his, he clearly didn't feel anything distressing.

    I am, of course, (arguably) a grown-up, but I've had my hands in cheap ultrasonic cleaners hundreds of times, and have never suffered any harm. Heck, these "50 watt" cleaners haven't even had enough power to give me a rash when I've been using water/detergent/alcohol mixtures to clean something really filthy and stuck my hands in then, to turn over the thing being cleaned, or whatever.

    You'd think there'd at least be a bit of cavitation around the base of your fingernails that'd make them sting, but I've never noticed even that, even with the stronger solvent mixtures.

    And yes, I stood there with my hand in my old cleaner (which was only filled with water...) for a few minutes once, just to see what would happen. The tingly sensation from my current big cleaner isn't any stronger than the sensation I got from my old small one. Actually, I think the new cleaner's less powerful for a given fill level, but the 30 minute timer more than makes up for that as long as I'm not in a hurry.

    So I think your concerns, while laudable, are unfounded.

    Try the foil test again with the foil wrapped in ham, and see how many holes develop then :-).

    (I'd also like to see what a 650 watt cleaner filled only to the "MIN" line can do to, say, a chicken drumstick.)

  6. Daniel Rutter Says:

    No, wait. That's no way for me to drum up traffic for my new and controversial blog.

    What I meant to say was:

    Yes! I flense the flesh from babies' bones! Hahahaha! Death to America!

  7. Picasso1387 Says:

    Actually, I think you just came up with an excellent name and tagline for your blog.

  8. jaranath Says:

    Thomas' expression is priceless, especially right after "I think you can see where this is going."

    I hope Ozzie and Sonicare are indeed "overcautious" about the risk of joint injury, though I admit I'll be a bit more hesitant to engage in my own bouts of unconventional infant cleansing.

  9. drzaius Says:

    I believe you may be on to someting here. In the name of science, you must get a large cleaner & a chicken leg & then report back

  10. Stark Says:

    It should be noted that ultrasound has been in theraputic medical use since the late 1940's. Not just as scanners but as therapy devices typically used for relievieng pain and stiffness associated with arthritis along with a number of other physical therapy applications. The transducers involved in most medical applications put out somewhere around 1 to 3W/cm2. So - from the photo it looks like the tank has a liter or so of liquid... which means that 50W input is spread through 1000cm3 which equals: .05W/cm3.

    So, if safe medical use (which admittedly does cause a reaction in tissues) allows for as much a 3W/cm2 and we're seeing around .05W/cm3... well, I'd say brief exposures are absolutely harmless. Now, I wouldn't leave my hand in there all day - it is likely that after long enough exposure it could begin to break down live skin and tissues - but I'd have no issues with up to 30 minutes or so... after that all you'd have is very clean hands (not a dead skin cell left on 'em I'd bet) but be none the worse for wear.... well, ok - you might have wrinkly fingers from the water. ;)

    Of course all bets are off if you use anyhting harsher than water. Stick your hand in an ultrasonic acetone bath and leave it there for 30 minutes and you'd most assuredly regret the decision.

  11. sid Says:

    Hello dan.. love dansdata. Just a quick thought before you file your patent though. Exposure to ultrasound has been shown to cause epiphyseal plate (the growth plate) disruption in children who haven't acheived skeletal maturity. Be careful will ya.

    Cheers.

  12. rsandor Says:

    This is a crazy idea. I've been told ultrasound kills cells. On my site we have an industrial model Elmasonic Transonic Ti-H ultrasonic cleaner. I know when I put my hand in the cleaner, it hurts! I wonder how if the baby is in pain?
    Robert Sandor

  13. daveo Says:

    What the f#@$. Whatch the unisonics ultrasonic cleaner put holes in this foil: http://www.unisonics.com.au/Content_Common/pg-performance-test-foil.seo
    mayb your cleaner is underperforming. :- 0

  14. gossumx Says:

    I did put my hand into my small ultrasonic cleaner that I got off amazon.com and it hurt with a tingly sensation.

    Maybe mine is stronger, but it doesn't seem safe. Well, after doing that I googled "hand in an ultrasonic cleaner", and I found this site (right below yours) in the search results.

    http://www.ultrawave.co.uk/faqs.php?id=16&pa=57#17

    It states that "It is advised that no part of the operator's body be submerged into the fluid during operation of the bath. Ultrasonic energy can cause damage to tjoint tissue, creating discomfort and skin irritation and even lead to long-term arthritic conditions."

    I'm not a scientist on the subject, but I would not advise this for a child until I saw someone else's scientific study.

  15. Daniel Rutter Says:

    Ultrawave make good ultrasonic cleaners. Mine is a cheap ultrasonic cleaner :-).

    Cheap cleaners never have high-powered transducers in them, since those are the expensive parts. If there's a reasonable amount of water in the cleaner, submerging your hand in it for even quite a long period of time is, I'm quite confident in saying, only marginally more dangerous than putting your hand in soda water.

    The baby in question is now approaching kindergarten age. His hands have yet to fall off.

  16. rwr104 Says:

    J Orthop Res. 2003 Sep;21(5):865-71. - The effects of therapeutic vs. high-intensity ultrasound on the rabbit growth plate.

    "This short-term study demonstrates that high dose ultrasound has profound pathologic effects in growing bone. Therapeutic doses of ultrasound do not have an adverse effect on bone growth in the short-term follow-up."

    I am a medical professional and own a private clinic. My thoughts are that in the domestic environment, the effects of damage to an epiphyseal (growth) plate may not be apparent for several years. The risk of injuring your child in an ultrasoniuc cleaner may be small but there is still a risk: are you prepared to take that risk?


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