Photolithography

Photolithography is commonly used in the semiconductor industry and in printing and it involves the transfer of a photomask image onto a flat surface.  In essence, a negative is exposed to a photo-sensitized surface. The image is then developed on the surface where the photosensitive groups have been activated by the light passing through the clear parts of the negative. 

Photopolymerizable hydrogels such as PEGDA or PEGTA-based hydrogels mixed with photoinitiators show great promise as biomaterials to use with photolithography since the hydrogels’ shape can be manipulated by the mask used and its physical properties altered by including peptide based cleavable sequences and cellular attachment sites¹.  For example, specific patterns of acrylated peptides in the presence of photoinitiator can be prepared on the surface of a PEGDA hydrogel by using a photolithographic mask². Photolithography can also be used in conjunction with PDMS stamps to fabricate PEG-based microstructures to capture and analyze cells in the context of a microfluidic channel³. 

References

1. Gobin AS and West JL, Cell migration through defined, synthetic extracellular matrix analogues. FASEB J. (2002).
2. Hahn MS et al, Photolithographic patterning of polyethylene glycol hydrogels. Biomaterials (2006) 27: 2519-24.
3. Khademhosseini A et al, Molded polyethylene glycol microstructures for capturing cells within microfluidic channels. Lab Chip (2004) 4: 425-430.