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Building a hair thin Mini hot tip (like soldering) Answered

Building a hair thin Mini hot tip (like soldering) Building a hair thin Mini hot tip (like soldering) Well as you read it I am trying to build a very very small heat controllable mini hot tip (max 40 degrees C) And definitely I am sure you are such an expert in the area that the hair hot tipwill sound like a joke to you. What for? well, long story short I want to put bacteria samples on it & gradually increase the temperature and see how the populations die or survive, and most likely how long they last, to demonstarte if actual dishwashers do a good job. (maximum temp boiling point) I actually want to record the video given to the fact that the microscope I have access at school is wayyyy more powerful than the rest. I know I should use an LED or just heat but what prevents me from doing so is just blowing away the samples from the tip or changing the exposure too much with extra lights. I believe the principle is almost the same as with the coil inside electric bulbs or the same as in ironing clothes but not as hot (in orders of magnitude) I believe the trick is driving voltage and just making variations to it with a dial please help I really want to see those bacteria and film them . All help will be appreciated Thanx Micro Freak apprentice



8 years ago

Guys, in the first place, dishwashing detergent does not attempt to kill bacteria by washing them with soap, but if you read the container, the stuff is pretty caustic. the soap breaks the surface tension (surfectant) and the combo of heat, water and caustic does the rest. not to mention that it removes grease pretty well by soapifying it. As for heating the bacterial samples to watch them die, how bout heating the slide that they reside on? that should not cause them to be 'blown away'.
I would offer that an IR laser, beam delivery Via fiber pipe should do the trick as well. it can be focused to a diameter as small as some of the bacteria them selves. use a good camera, for the main event, as the cheap ones will see the IR as well as the visible spectrum. but a cheap one at the same time would allow one to see where the spot is at any given moment.


10 years ago

Did you really mean *40 degrees Celsius* max? That's about 104 Fahrenheit - a hot day in the sun, but not exactly diswasher temperatures, nor anything too many bacteria will have trouble with...

Most enzymes denature around 40 - 45 degrees.

. You probably need to use something larger. Trying to regulate the temperature of a small wire will be difficult enough, but accurately measuring the temp, without disturbing the system, will be next to impossible for a DIY project. I'd try something along the lines of Kiteman's idea (even if you are using a "safe" bacteria, it's just good practice to isolate it).

If you want a hair-thin tip, you could use Nichrome wire...I don't know how inert it is, though. You could vary the heat using an LM317, like westfw said. There's even an Instructable for it.


10 years ago

What are the size requirements? I would think there would be some significant advantages to using something like a light-bulb; glass being nice and inert compared to metals you might make a filament out of. It's a season where most stores are selling relatively small lightbulb in strings of 100 or more at discounted prices, but smaller "grain of wheat" bulbs are available year-round from the right places. I'm not entirely sure how you'd measure the temperature at the glass surface, though, or whether it reaches the sort of temps that you need. (Bigger 5-50W halogen bulbs can reach quite substantial tempetatures!)

Thanks west, well definitely what you say makes sense, and I tought of implementing that but now I am using a very expensive microscope that is property of the school and I really want something I can take to school and then back home that is why the filament is exciting, ii have been trying with a resistor and a battery but I do not know how to vary the voltage in a controlled way to gradually increase the temperatures... the ideal would be the filament or filaments controlled by a dial to ncrease the voltage gradually and therefor the temperature. Any ideas?

You could use a variable voltage regulator, I think, like an LM317, in it's reasonably standard "variable voltage" mode. I was working on a design to use a 327 as a motor speed control for the sort of small hobby motors that abound, and it seems pretty doable. One normally thinks of using either a more complex circuit (microcontroller, PWM, etc) or a simpler circuit (transistors), but the 317 is pretty common, pretty cheap, easy-to-use, has built-in protections mechanisms, so I can't really think of good reasons not to use it even if a simpler transistor circuit might be possible. It should drive a filament, light bulb, or resistor "heating element" with nearly equal utility. (it might be tough to get a filament with high enough resistance...) A difficulty might be figuring the voltage to temperature relationship.

oh man its great when you expalin difficult things the easy way... Thanks I am back to the designing board !

If I was advising a student about an experiment to investigate the effect of temperature on the reproductive rate and population stability of bacteria, I would expect them to apply the heat over several hours or days, using a thermostatically-controlled incubator. I would expect to see the samples grown in properly-inoculated Petri-dishes, sealed against the possible escape of dangerous pathogens or ingress of contaminants. I would expect to see multiple samples incubated at each selected temperature to increase the reliability of the data. If any student proposed heating the bacteria with a jet of air directly onto the sample (i.e. growing the bacteria in an un-sealed container), I would prevent them doing the experiment at all.

I would expect to see multiple samples incubated at each selected temperature to increase the reliability of the data.

Not to mention prevention of the spreading of any harmful bacteria grown in the experiment.


...sealed against the possible escape of dangerous pathogens or ingress of contaminants.

Yeah, sorry.....I really should avoid posting in the wee hours of the morning....my eyesight seems to be severely lacking then. My apologies.

Keep in mind that the soap kills bacteria. Dishwashers don't sterilize using hot water...for that you'd need an autoclave (120 degrees C)

I think that the 120C is to ensure things like prions break down. The vast majority of microbes can't survive past 60C.

Soap doesn't kill bacteria unless it is also antiseptic. The soap is there to break down hydrophobic substances such as grease and fat into particles small enough to be washed away.

The soap actually makes the water, wetter too. That is, it breaks the surface tension of the water, and allows it to wash the dirt away. Soap doesn't really do as much cleaning as the universal solvent does ;-)

The soap breaks down them down, but is should be antibacterial as well. A quick look at my dishwasher soap say that it has bleach in it. Besides (possibly helping with) color, that would also help kill bacteria, no?

If it's concentrated enough, yes, but the cynic in me says it's there to decolourise anything the dishwasher can't shift.