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Photoresists

  • Photoresists are light sensitive materials
  • Typically used as coatings
  • Light is used to form an image on the coated surface, using a photographic negative
  • The exposed image is developed using a solvent
    • Some of the photoresist remains to protect the surface
    • The photoresist pattern is a precise copy of the image on the negative
    • The rest of the surface is uncoated and subject of further treatment
  • The photoresist image is also called a mask

Photoresists are capable of producing patterns of extremely fine detail and have important commercial applications:

  • Photolithography and printing
  • Decorative arts including glass
  • Computer chips and circuit boards
  • Nanotechnology
  • Electroforming of intricate metal objects

The selected example illustrates the process of electroforming metal patterns using a photoresist mask.

Materials

  • Small sheet of polished stainless steel, 1”x2”
  • Photoresist stencil on a thin plastic sheet
  • Electroplating bath containing a solution of copper sulfate
  • Copper wire as cathode (positive electrode)

Procedure

Photoresists Experiment MaterialsAn office copier or a laser printer is used to copy a pattern on a special (blue) paper. The pattern can be transferred to a sheet of stainless steel using a hot iron to obtain a thin layer of photoresist. The metal sample is then placed in an electrochemical bath and is electroplated with a film of copper metal.

Because the transfer pattern acts as a mask, metal is only deposited in the uncovered regions. When the metal deposited has reached a sufficient thickness, it can be lifted from the surface using a razor blade (Figure 1). The result is a metal object with delicate details that duplicate the pattern of the original drawing (Figure 2).

Close up of experiment

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Other Demos: Chemiluminescence of Luminol, Photoresists, High Energy Emitters for Organic Light-emitting Diodes, The Spectrum and Complementary Colors, "Titrations" with Dry Ice, The Red-White-Blue Clock

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