Introduction: UV Transilluminator

UV-transilluminators are used in molecular biology labs to view DNA (or RNA) that has been separated by electrophoresis through an agarose gel. During or immediately after electrophoresis, the agarose gel is stained with a fluorescent dye which binds to nucleic acid. Exposing the stained gel to a UVB light source causes the DNA/dye to fluoresce and become visible. This technique is used wherever the researcher needs to be able to view their sample, for example sizing a PCR product, purifying DNA segment after a restriction enzyme digest, quantifying DNA or verifying RNA integrity after extraction.

This Instructable tutorial describes how to make a UVB (310nm) transilluminator with a 7 x 7 cm window for viewing ethidium bromide (or SYBR-Safe) stained DNA mini-gels. Once all of the materials are collected, the actual assembly time is approx. 1-2 hours. Some soldering is required.

Safety Notes:

  1. Because ethidium bromide is a toxic chemical with strict safety protocols, it is only recommended that you use this dye in a lab with established handling, storage and waste disposal procedures in place. Other users are strongly recommended to use SYBR-Safe instead, which can be handled and disposed of more safely.
  2. The transilluminator does come with a safety lid for viewing the gel. However, when the lid is not in place, safety glasses mustbe worn when operating the UVB bulb.
  3. If you prefer to avoid UVB altogether, we can recommend the blue light LED transilluminators such as the one described in this instructable instead.

Step 1: Materials: Laser Cut Acrylic Parts

For the UV transilluminator enclosure and lid, download the design file attached below (svg or PDF file). Laser cut the parts from the material listed in the design file. If you do not have access to a laser cutter, you can send the files to any laser cutting service such as Pololu. Materials for laser cutting can be found at any supplier of acrylic materials (McMaster-Carr, US Plastics etc) except for the solacryl (UV-transmissive) which can be bought from Loop Acrylics.

Tap holes in the following parts:

  • 5-40: Two holes in the enclosure side with the cutout for the power switch
  • 8-32: Four holes in the solacryl cover
  • 8-32: Four holes in the 0.25" clear lid side part for mounting the hinges
  • 8-32: Two holes in the enclosure bottom

A video of hand-tapping acrylic can be found here:

Step 2: Materials Contd: UV Bulb, Filter and Other Hardware

1 x 312nm Ushio 9W GPX9E UV bulb Cat # 11_2122, Fotodyne:
1 x ballast and G23 lamp holder Cat # 163141.02, Atlanta light bulbs:
1 x U325C transilluminator glass, 7 x 7 cm, HOYA Corporation:
1 x power entry and switch. Cat # CCM1906-ND, Digikey:
1 x 6' power cord. Cat # 132118, Jameco:

4 x Plastic Bumper. Cat # 9405K61, McMaster-Carr:
4 x 10-32 standoff, 2.5” long. Cat # 92230A140
4 x 10-32 machine screw, 1” long. Cat # 91249A272
4 x 10-32 machine screw, ½” long. Cat # 91249A263
2 x 5-40 Thread, ½" long. Cat # 91772A128
2 x 8-32 Thread, ¼" long. Cat # 91772A190
8 x 8-32 machine screw, 3/16” long. Cat # 91771A189
2 x Hinges Cat # 1598A52
2 ft x 14 Gauge general purpose wire. Cat # 7587K98

1 x IPS weld-on cement #3 or 4, Cat # 10792, TAP Plastics:
1 x Hypo-type solvent cement applicator, McMaster-Carr, Cat # 25658


  • Philips screwdriver
  • Soldering iron and solder
  • Wire clippers

Step 3: Connect AC Power to Ballast

  1. Place the power entry and switch into the laser cut back part and secure in place with the two 1/2" long 5-40 machine screws.
  2. Connect neutral and live wires to ballast as shown in the images
  3. Solder the neutral wire and live wire to the plug connector as shown in the images.

Step 4: Assemble the Enclosure

  1. Take one of the 1" long 10-32 machine screws and thread it through one of the rubber feet and the corner holes on the bottom enclosure part. On the opposite side of the enclosure, screw in one of the 2.5" long 10-32 standoffs. Repeat for all 4 corners of the enclosure bottom.
  2. Place the ballast in the middle of the enclosure and fasten down with two of the 1/4" long 8-32 screws. Make sure that the ballast is oriented as shown in the images.
  3. Put the UVB bulb into the ballast and place the remaining enclosure parts into the slots in the enclosure bottom.

Step 5: Assemble the Cover

The top part of the transilluminator includes the transilluminator glass covered with the solacryl UV-transmissive protective cover.

  1. Place the lower lid onto the top. It will be secured in place by fitting it over the tabs on the enclosure sides.
  2. Lay the upper lid onto the lower lid.
  3. Place the transilluminator glass into the slot on the upper lid.
  4. Place the UV-transmissive protective plate over the enclosure.
  5. In each corner screw in the four 1" long 10-32 machine screws to secure all 3 top layers plus transilluminator glass in place.

Step 6: Assemble the Hinged Safety Lid

In the final assembly steps we will add a hinged safety lid. The top part of the lid is 1/8" clear acrylic which will block UV light. (Note: you should use safety glasses if you will be operating the transilluminator at any time without the lid.)

  1. Using the Weld-On acrylic glue and applicator, weld the 1/4" acrylic sides onto the 1/8" base.
  2. Attach the two hinges to the lid using four of the 3/16" long 8-32 machine screws.
  3. Attach the hinged lid to the top of the enclosure as shown using the remaining four 1/8" 8-32 machine screws.

Step 7: Viewing a Gel

Preparing an electrophoresis gel is a whole other tutorial so for now I would recommend reading this excellent Instructable for preparing the gel:

and this Instructable for making your own electrophoresis system:

Once you have your gel prepared, place it onto the transilluminator above the viewing window, put the hinged safety lid down and switch on the transilluminator. At this point you should see your DNA bands.