I need to buy a UV lamp for polymerization of various photoreactive samples. The most important application will be in polymerizing liquid crystal mixtures containing reactive mesogens, to which photoinitiators have been added. Since liquid crystals may change their behavior or even phase upon temperature changes I need to minimize sample heating during UV curing, and it would probably be good to be able to change the intensity so I can control the polymerization time as well as adapt to different sample size and character. Most often my samples will be rather small, on the order of a square centimeter cross section or less, so I need focused rather than broad and diffuse illumination. In fact, it may even be very useful if I could perform highly localized UV curing in samples mounted on microscopes. I have seen quotations ranging from a few hundred US dollars up to 10,000 dollars. I am quite bewildered, since I do not have experience of my own here. If anyone can suggest a good model for my purposes and/or tell me what a high-priced model typically delivers that a low-priced does not, that would be extremely helpful.
Dear Jan,
doesn't this sound like a typical application for UV LEDs?
Pro: very small device (but see also cooling demands), can be focused to a small area, almost no heating of the sample, can be arranged in your microscope.
Contra: narrow frequency band (must fit to the polymerization you want to perform), complicate dimming, maybe too low peak irradiance, cooling necessary.
There are a lot of commercial LED curing devices on the market for applications in printing, coating and adhesives.
But for your application in microscopy I would think about a self-made device, e.g using high performance LEDs. They differ in wavelength(365 nm, 375 nm, 405 nm), angle of radiation (110°, 130°) and power (75 mW – 500 mW). I would suggest some experiments e.g. with some P8D240 500 mW (cf. technical description) focusing on the same small spot. Depending on your specific polymerization problem you may need about 4 W/cm2 for curing but I would start maybe with 1-4 LEDs for testing. The LEDs must be cooled during operation, this might be somewhat difficult regarding the spatial situation in the microscope.
******
*** Protect your eyes!
*** Even the reflections may seriously harm your eyes!
*** And you do not see the danger:
*** The UV spectrum is invisible for us.
******
Regarding the price you would end up with a few hundred US dollars for such an experimental device.
Hi dear
there is good instrument for UV crosslinking
it is from spectonics Corporation, model no is SPECTRO LINKER, XL 1500, UV ceoasslinker, I think ther is no need to worry about heating, bcz u can work at room temp. with this instrument
It is better to choose the UV Curing machine. In order to reduce the heat effection , you can enhance the circulation in a fumehood
A self build LED system is likely your best approach. Photoinitiators tend to have a broad absorption spectrum, for instance 360nm to 405nm. It is important not to provide too much energy to your photoinitiator. Doing so will cause your photoinitiator to react too quickly leaving you with unpolymerized product. Managing the irradiance at the sample will be important. This is convenient with LED as dimming is possible. UV LED cost increases significantly as you move away from 450nm. For a self build I would reccomend starting with UVV LEDs. I am assuming your photoinitiators apsorption spectrum is in this region, if not move to UVA, then UVB etc. Ultra Violet Visible are the most economical availible UV LEDs. They are commonly used in aquariums to facilitate coral growth which requires the Superatinic light from UVV LED. If you would like to apply the light to your samples while under a micrscope you may consider using a quartz light guide. A short light guide coupled to your LED/LEDs will provide flexibility and concentrated light on the product. Light where you need it not where it comes from. A good example of this is curing systems used by dentists. One of these off the shelf systems may be a good alternative to a seld build, the cost will be significant however.
Dear Jan,
I am convinced that you have found an adequate solution. At the moment I use mounted LED-devices (ThorLabs).You should also take in mind that initiators are not optimised for LED radiation. Considering systematic studies I would suggest using a continuous (or discontinuous) XENON light source, a water filter (IR radiation) and specific variable filter (attached publication). For large scale syntheses a lab curing unit equipped with a suitable LED unit (compare to IST Metz) is a good solution.
Article Method to analyse energy and intensity dependent photo-curin...
- Badges
- Science topic