My DIY UVC light sterilizer!

Ever want to sterilize something without having to douse it with bleach or alcohol or use 1000 degrees of heat? Okay-that may not sound exciting, but I wanted to work on some non-invasive sterilization for a few projects. Alright, I wanted to see if I could sanitize my sandals and shoes with UV light to prevent them from smelling.

So after a bit of research on some DIY projects, I actually found this nice self contained UV light kit. Being able to dry my nails was just a bonus.

Unfortunately, the compact florescent UV lights didn't seem to do the trick. Upon further research, I needed UVC light, light that operated in the 254 nano meter (nm) wavelength. The light bulbs in the nail dryer operated at 365 nm.

It was pretty easy to locate UVC light bulbs with the same G23 connector. UVC lights are used heavily in aquariums and air filters. I found a generic pair on Amazon that suited the bill.

UVC bulb. It's generic and cheap and supposedly 245nm.

Built with a bit more quality and presumably certified. 365 nm.

Side by side. UVC bulb on top, CFL UV light on the bottom.

For around 12 dollars, I was able to buy 2 UVC bulbs on Amazon. They are rated for 8,000 hours, but I will be satisfied if I only get a few thousand for the price.

The new bulb came moderately protected. It was in a plastic envelope, wrapped in bubble wrap in a cardboard sleeve. I pulled 4 of the original ones out and replaced it with 2 of the new UVC lights. Hit the button and  .  . . nothing. Oh wait, is this light suppose to be visible. Is the light broken?

It turns out that the UV light box has a number of options to set a timer and I was pressing the wrong buttons. So a nice bluish light started flowing from the box. Victory!

Just don't look directly into the light!

So how was I going to find out if this thing actually kills any bacteria? Well-by killing some bacteria!

With the botched gelatin samples I ran earlier in the week, I had 6 petri dishes still sitting in the fridge. (BTW-my wife loves that I have experiments now taking up room in our fridge.) To test the effectiveness of the UVC light I ran through the following scenarios:

1. #11 Exposed 30 minutes to air by kitchen sink
2. #12 Exposed 30 minutes to air by kitchen sink. Then Exposed to UVC light for 1 hour
3. #13 No exposure. Kept sealed from fridge to incubator (oven).
4. #14 Swabbed from kids computer keyboard.
5. #15 Swabbed from kids computer keyboard-exposed to UVC light for 1 hour
6. #16 Swabbed from kids computer keyboard-exposed to UVC light for 3 hours.

My hypothesis was that #12, #15, and #16 were going to show no or very little bacterial growth. Let's see if the results back my theory. After sitting in my incubation chamber for 1.5 days they kinda of do . . .

#	Test	Control	Image
11	Exposed 30 minutes to air by kitchen sink. 3rd clearest dish. Not the result I was expecting. Possibly mixed switched #12.	Y
12	Exposed 30 minutes to air by kitchen sink. Then Exposed to UVC light for 1 hour. Not the result I was expecting. Possibly swithced with #11.
13	No exposure. Kept sealed from fridge to incubator (oven). Some mold growth, but not as much as those intentionally exposed.	Y
14	Swabbed from kids computer keyboard. As expected-mold growth.	Y
15	Swabbed from kids computer keyboard-exposed to UVC light for 1 hour. Victory-look at the clear gelatin.
16	Swabbed from kids computer keyboard-exposed to UVC light for 3 hours. Victory-look at the clear gelatin.

The most obvious are that 15 and 16 are crystal clear. There was very little bacterial growth in the medium. If you looked very carefully, there was growth on the bottom of the petri dish-suggesting that that the UVC light attenuates before it can reach the bottom of the petri dish.

Both the swabbed dishes exposed to UVC light are very clear. There is some growth on the very bottom of the dish.

Side by side of the swabbed dish exposed to UVC for 1 hour (#15) and the swabbed dish (#14).

Side by side of the swabbed dish exposed to UVC for 1 hour (#15) and the dish exposed to air for 30 minutes. I think I might have placed #11  this dish under the UVC light as well--but will need to reconfirm.

Side by side of exposed to air (#11) and exposed to air with 1 hour of UVC light (#12). I think I reverse the samples.

Side by side of exposed to air (#11), exposed to air + UVC (#12), and no exposure (#13).

Dishes 11 and 12 gave some mixed results. I was expecting to see the growth of 12 in 11 and vice versa. This leads me to believe that I either placed the wrong dish under the UV light. I can't discount these results and will need to re-run this test again with better gelatin and agar.

So while I am pending some final conclusions, I think I built a pretty good and self contained sterilizer unit for less than 40 dollars.

Let me know if you have any other uses for a UVC sterilizer.
Cheers!
Jason

UVC Light bulbs

http://amzn.to/2rParZh

UV Nail Gel dryer
 http://amzn.to/2sL9kia