Photolithography

Photolithography is a relatively new m icrom anufacturing technique in w hich polym ers are exposed to selectively to light energy in order to define a three dim ensional shape. Selective exposure is either through a m ask to produce a uniform cross-sectional shape, or by scanning a focussed point o f light through the target polymer, or “photoresist,” to produce non-uniform cross-sections. Light energy

defines shapes w ithin the resist either by curing the polym er (positive photoresists) or ablating it (negative photoresists) at the point o f exposure. Shorter w avelength light defines shapes m ost accurately, and X -ray lithography is capable o f producing com plex shapes w ith subm icron accuracy. These accurate solid representations o f designs on a m icron scale can be used either to create prototype devices individually, or to create m icro-m oulds for scale up to bulk m anufacture.

5.3 C onclusion

The health econom ic argum ents for developing a fast, reliable, one-stop treatm ent glaucom a are clear, particularly in the developing w orld, w here access to regular review and drug treatm ent is likely to rem ain limited. Laser drilling has not been accurate enough to realise the goal o f producing a biocom patible GDD to im prove flow control and reduce operating tim e in routine GFS. Em erging techniques for m icro-m anufacture such as X -ray lithography hold im m ense prom ise in this field. Possibilities for fusing these techniques w ith im provem ents in material biocom patibility and advances in the pharm acological control o f w ound healing suggest a bright future for G D D s in the new century.

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