How to make a message glow using your smartphone

Making a "UV light" at home in just 5 minute

Safe­ty pre­cau­tions


Reagents and equip­ment

  • smart­phone;
  • tape;
  • blue mark­er;
  • pur­ple mark­er;
  • high­lighters (yel­low, green, or­ange);
  • sat­u­rat­ed flu­o­res­cein so­lu­tion;
  • Petri dish;
  • pa­per.

Step-by-step in­struc­tions

Cov­er the smart­phone light with tape and col­or the tape blue. Add an­oth­er lay­er and col­or this lay­er pur­ple. Re­peat twice. Add one last (clear) lay­er of tape as a pro­tec­tive cov­er­ing. Use the high­lighters to write a mes­sage on the piece of pa­per. Turn off the light and il­lu­mi­nate the mes­sage with your makeshift UV light. The mes­sage glows! Re­peat the ex­per­i­ment us­ing flu­o­res­cein. Add a few drops of sat­u­rat­ed flu­o­res­cein so­lu­tion to a Petri dish full of wa­ter. First shine your smart­phone light on it, then ex­pose it to the UV light. No­tice the green glow un­der the UV light.

Process de­scrip­tion

Sim­ply put, light con­sists of elec­tro­mag­net­ic waves of var­i­ous fre­quen­cies. When we cov­er the smart­phone light with lay­ers of col­ored tape, we cre­ate a light fil­ter of sorts, which only al­lows ul­tra­vi­o­let waves – UV light – through. Flu­o­res­cein and high­lighter dyes are lu­mi­nes­cent, mean­ing that it re­leas­es light fol­low­ing the ab­sorp­tion of light waves such as UV light.