The Effect of pulsed Microwaves on Bacteria

In summary, the conversation focused on using pulsing microwaves to investigate their added kill effect on bacteria. The participants discussed the mechanism of action of microwaves on living organisms, which is still not fully understood. They also mentioned previous research on the topic and the need for specialized research equipment to generate and control microwave power. One participant shared their experience with using low levels of microwave energy to destroy bacteria on medical and dental instruments. The conversation ended with a note of encouragement and an offer of help for any problems that may arise during the experiments.
  • #1
uncle albert
2
0
We are interested in looking at the effect of the pulsing of microwaves subjected to power and time of eg 50W for 10 seconds at 2.45GHz but pulsing the microwaves as well to investigate the added kill effect that the pulsing adds, comparing plate counts before irradiation, after non pulsed irradiation and then after pulsed irradiation.

Does anyone have any suggestions/recommendations or does anyone know of any literature or papers and where we could get some pointers about the mechanism of action of the pulsing?

Cheers for nowAndy/Uncle Albert
 
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  • #2
Well, http://dx.doi.org/10.1006/jtbi.2000.2123" [Broken].

As for the mechanism, I think it's safe to say the exact effects in living things are unknown. But to sketch out the general "physical chemistry of microwaves for biologists":

Microwaves correspond to dipole moment excitations in molecules; i.e. increased vibration and rotation of molecular bonds in polar molecules.
In a simple molecule (e.g. water) this quickly degrades into heat (vibration/rotation/bumping around in general), but in a delicate macromolecule (read: proteins, DNA, etc) the local 'heating up' of a single bond or two can lead to conformal changes/denaturation as the bond(s) could suddenly rotate well outside its 'usual' range. Which is also what's been observed.

The short answer is: 'heat'. But of course, usually when we talk heat we mean bulk heat which is evenly distributed. Whereas with microwaves, especially if you pulse them, you're more-or-less making specific spots very 'hot' very quickly; and things might occur before they 'cool down' again. (quotes because heat is really a macroscopic property) So you could view it as thermal shock, or partial thermal shock. (which may be worse, given that we're probably evolved to cope better with even heating)

Obviously both bulk heat itself and denaturation are capable of killing things, and in many different ways. But as a chemical physicist, figuring that bit out is not my department. :wink: But there's no single mechanism for sure, any more than there is for say, how cancer is caused.

(Note for layfolks: I'm not saying here that I believe microwave ovens/cellphones/wifi/etc are a significant health hazard. I do not. There's simply too little power. Suntanning is far worse)
 
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  • #3
There have been many papers on killing bacteria with microwaves i.e. Olsen, C.M. et. al., J. Microwave Power, Vol 1, # 1 (1966) is a very early paper. It and following research indicates that all bacterial destruction is thermal. In my own case I have a number of patents using low levels of microwave energy to destroy bacteria on medical and dental instruments.

There is a more fundamental question: how to generate 50 watts of microwave energy. You cannot use a domestic oven to do this. It takes research equipment, and that's not cheap. Think $ 5,000 and higher. I have such an oven that sells for about $ 20,000. Pulsing is not difficult and the oven manufacturer can likely provide you with such a system.
 
  • #4
microwaveguru said:
There have been many papers on killing bacteria with microwaves i.e. Olsen, C.M. et. al., J. Microwave Power, Vol 1, # 1 (1966) is a very early paper. It and following research indicates that all bacterial destruction is thermal. In my own case I have a number of patents using low levels of microwave energy to destroy bacteria on medical and dental instruments.

There is a more fundamental question: how to generate 50 watts of microwave energy. You cannot use a domestic oven to do this. It takes research equipment, and that's not cheap. Think $ 5,000 and higher. I have such an oven that sells for about $ 20,000. Pulsing is not difficult and the oven manufacturer can likely provide you with such a system.


We have just bought equipment that will allow us to vary the power setting from 0 to 300 W and have been playing around to find out what we can do with it. The problem we have at present is the reflected power but we are working on that aspect.
Thanks guys for your help. It has been really productive.

Andy
 
  • #5
Andy
Good luck. This sort of experimenting is difficult - I've been doing it for 50 years. If you need help list your problems.
 

1. How do pulsed microwaves affect bacteria?

Pulsed microwaves can have a variety of effects on bacteria, depending on the specific frequency, intensity, and duration of exposure. Some studies have shown that pulsed microwaves can lead to changes in the cell membrane, DNA damage, and altered metabolism in bacteria.

2. Are there any potential health risks associated with exposure to pulsed microwaves?

Currently, the research on the health effects of pulsed microwaves on bacteria is inconclusive. Some studies suggest potential risks such as antibiotic resistance and altered gene expression, but more research is needed to fully understand the long-term effects.

3. Can pulsed microwaves be used to kill bacteria?

Yes, some studies have shown that pulsed microwaves can effectively kill bacteria. However, the effectiveness of this method may vary depending on the type of bacteria, the intensity of the microwaves, and other factors.

4. How do pulsed microwaves compare to other methods of disinfection?

Pulsed microwaves are still a relatively new method of disinfection, and more research is needed to compare its effectiveness to other methods such as heat, UV light, and chemical disinfectants. However, some studies have shown that pulsed microwaves can be as effective or even more effective in killing bacteria.

5. Can pulsed microwaves be used to control bacterial growth in food?

There is ongoing research on the use of pulsed microwaves to control bacterial growth in food. Some studies have shown promising results in reducing bacterial contamination in food, but more research is needed before it can be used as a widespread method for food safety.

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