Battery-Powered Plasma Flashlight Makes Short Work of Bacteria 133
cylonlover writes "An international team of scientists has created a handheld, battery powered device that has been shown to effectively rid skin of bacteria in an instant by blasting it with plasma. The plasma flashlight, which shouldn't be confused with a plasma torch that will damage much more than bacteria if used on the skin, could provide a convenient way for paramedics and military personnel to deal with harmful bacteria in the field. The self-contained device is powered by a 12 V battery and doesn't require any external gas feed or handling system. The plume of plasma it generates is between 20-23C (68-73.4F), so it won't damage the skin. It is also fitted with resistors to stop it heating up and becoming too hot to touch. Its creators say it can also be easily manufactured at a cost of less than US$100 per unit."
Real science, please (Score:5, Informative)
"It is also fitted with resistors to stop it heating up and becoming too hot to touch."
Um. What? Whoever wrote this clearly has no electronics knowledge. This is Slashdot. We have real engineers and scientists around here. Could we have real science reporting, please? Not only is that sentence moronic, the entire article fails to explain how this device operates, even in the most basic terms. It's shaped like a flashlight, but that seems to be where the similarity ends. It is not a light source whatsoever. From the actual scientific publication, it appears that this is a high voltage pulse generator that produces a discharge between the device and the patient. A series of 100ns pulses at 20KHz repetition rate ionizes the air between the device and the patient, thus producing the ions that kill the bacteria. The peak current is 6mA, but the average current (and thus average power) is very low so heating is minimal. This is a relatively low-tech device electronically, and could easily be replicated by many hobbyists.
Re:Is it really the plasma, not the ozone or UV? (Score:5, Informative)
There's a paywall? Didn't notice, but here you go:
Battery-powered plasma flashlight makes short work of bacteria
By Darren Quick
00:51 April 5, 2012
An international team of scientists has created a handheld, battery powered device that has been shown to effectively rid skin of bacteria in an instant by blasting it with plasma. The plasma flashlight, which shouldn’t be confused with a plasma torch that will damage much more than bacteria if used on the skin, could provide a convenient way for paramedics and military personnel to deal with harmful bacteria in the field.
The self-contained device is powered by a 12 V battery and doesn’t require any external gas feed or handling system. The plume of plasma it generates is between 20-23C (68-73.4F), so it won’t damage the skin. It is also fitted with resistors to stop it heating up and becoming too hot to touch. Its creators say it can also be easily manufactured at a cost of less than US$100 per unit.
In an experiment carried out by the scientists, the plasma flashlight effectively inactivated thick biofilms of Enterococcus faecalis, a bacterium that often infects the root canals in dental treatments and is highly antibiotic- and heat-resistant. Created by incubating the bacteria for seven days, the biofilms consisted of 17 different layers of bacteria. After treating each biofilm with the plasma flashlight for five minutes, the plasma was found to penetrate deep into the very bottom layer and inactivate the bacteria.
“In this study we chose an extreme example to demonstrate that the plasma flashlight can be very effective even at room temperature,” said co-author of the study, Professor Kostya (Ken) Ostrikov, from the Plasma Nanoscience Centre Australia, CSIRO Materials Science and Engineering. “For individual bacteria, the inactivation time could be just tens of seconds.”
While plasma has previously been shown to effectively kill bacteria and viruses on the surface of the skin and water, the exact mechanism behind this is still not understood. Ultraviolet radiation has been theorized as a reason, but the jet created by the plasma flashlight is low in UV radiation, which adds to the safety of using the device on a person’s skin. The reactions between the plasma and the surrounding air has also been suggested as another possibility.
The international team behind the plasma flashlight consists of scientists from Huazhong University of Science and Technology, CSIRO Materials Science and Engineering, The University of Sydney and the City University of Hong Kong. Their work is detailed in the Journal of Physics D: Applied Physics.
Source: Institute of Physics
Re:Is it as effective as ozone? (Score:4, Informative)
Re:No thanks. (Score:5, Informative)
Oh, Mickey. His nickname says that he is an adult film producer. :P
Re:Real science, please (Score:4, Informative)
"It is also fitted with resistors and shit to stop it heating up and becoming too hot to touch."
That better?
Re:Real science, please (Score:4, Informative)
Shaped like a flashlight? Really? It looks like a crayon.
The article is http://iopscience.iop.org/0022-3727/45/16/165205/pdf/0022-3727_45_16_165205.pdf (may need registering, but it's free to download for a month)
The summary is semi-correct, but phrased terribly. The resistors provide enough ballast to limit the output power to 60mW. If you short the device the combined 100MegOhm is only going to dissipate a Watt of power. It's not so much to stop the device being warm to the touch, it's to stop the device from blowing up and/or burning your patient.
If they weren't there then you're essentially trying to dump 10kV into a human body which is roughly 10kOhm to be conservative. The resistance of air is about a megaOhm per centimetre, but presumably if it's arcing due to the plasma it'll have negligible resistance after ionisation. What would probably happen is the DC converter would blow up, but you'd get a pretty nasty shock.
Similarly as the human body has a maximum resistance of a few hundred kOhm, the plasma current is dominated by the two ballast resistors. Incidentally, it looks like the patient will either need to be wired up or will have to disinfect themselves because the thing works by pulling your body to ground with respect to the electrodes.
Re:No thanks. (Score:3, Informative)
Based on nearly every emergency room doctor asking me if I have an allergy to Penicillin [wikipedia.org] during the medical history part of the interview I figured it was an actual real thing. Still, just in case, I found this Wiki page talking about Penicillin drug reactions [wikipedia.org] that covers allergic reactions and has links to some studies or some such thing.
Honestly I'm not really well versed in the nitty gritty medical terms so I didn't entirely understand everything on the page, but I figure if its important enough for a doctor I've never seen before to ask me about then that means there's likely some people who are allergic to anti-bacterial agents.
Re:No thanks. (Score:2, Informative)
Penicillin is an antibiotic. When people speak of antibacterials they're usually referring to things you apply topically/externally, like iodine, alcohol, and peroxide.
Haptens (Score:5, Informative)
That said, I've never heard of an allergic reaction to either a simple alcohol or hydrogen peroxide. Skin irritation, sure, but not an allergic reaction.
Iodine is another matter. Antibacterial iodine is usually povidone-iodine, and it definitely is possible to have a severe allergic reaction to it. Various sources disagree as to why this happens, but it definitely does.
It's also possible, although rare, to have an allergic reaction to iodine-based contrast dyes. My mother nearly died from an injection some of this stuff, as a matter of fact.
Re:Real science, please (Score:4, Informative)
No, because resistors generate heat when current flows through them.
Yes, but that doesn't necessarily mean the total heat dissipated increases. If you have a constant voltage supply (typical), adding a resistor in *series* with the load *reduces* the total power dissipated. Yes, the resistor generates heat, but that is more than offset by a reduction in the heat generated by the load.
If a resistor in series with the load reduces the current by 1/2, the power dissipated by the load is reduced to 1/4 what it would be without the load.
Constant voltage is the most common case, as it is supplied by outlets and batteries, but some power supplies provide constant current, in which case adding a resistor in series would not alter the load power dissipation, and (as you are asserting) the heat generated by the resistor would add to the net heat dissipation.
Supposing you're driving an LED (disclaimer, I am not an LED lighting engineer), you'd want to keep it in the correct current range, so you'd use a constant current power supply. If you put a second identical LED in series with the first, you'd double the load resistance [note 1], but the power supply's voltage would adjust so the current remains the same. The Captain Obvious result is that if you drive 2 serially connected LEDs off your constant current supply instead of 1, the power dissipated doubles. The somewhat less obvious result is that if you're using a constant voltage supply the total power dissipated drops, so the the power dissipated by each of the two LEDs is less than one half what a single LED would.
note 1: LEDs aren't linear in their response like a plain resistor, so this wouldn't necessarily be true if we were talking about a constant voltage supply like a battery.