Student Project Abstracts 2005 - Pluto - University of Washington

HYDROGEL MATERIALS FOR TWO-PHOTON MICROFABRICATIONSolution Ethylene glycol dimethacrylate 1-vinyl-2-pyrrolidinone 2-Hydroxyethyl methacrylateA 1 1 1B 2 1 1C 1 2 1D 1 1 2Table 1.1. Hydrogel CompositionsRESULTSIt was found that setup 1 allowed the UV light to penetratethe resin-substrate interface in order to yield sufficient crosslinking.Sample A with a 1:1:1 ratio of EGMA, VP, and HEMA, andC with a 1:2:1 ratio of EGMA, VP, and HEMA gave the mostcrosslinking in the least amount of time. Composition C crosslinkedin 3 minutes, whereas composition A required 7 minutes,and compositions B and D could not be crosslinked. This wasdetermined by observing how much of the sample became solidafter UV exposure. Only the part of the sample behind the openingin the mask should crosslink. Samples that did not yield sufficientcrosslinking remained in the liquid state after UV exposure.Composition C was also used in the UV mask experimentsdue to its ability to yield higher crosslinking than compositionA. Table 1.2 contains data on swelling ratios in the bulk materialafter exposure to UV light at various times. The diameter and thethickness of the samples were measured before and after swellingin water overnight. Setup 1 was used with composition C,with exposure times of 5, 10, 15, 20, and 25 minutes. The resultsindicate that the bulk materials of composition C swell 4-5 timesits original size. Most of the swelling was observed to be in thevertical direction. Setup 2, which includes a mask, was used withcomposition C for 3 minutes. Picture 1.1 shows an example ofstructures obtained by photo-patterning of composition C througha mask. The width of the features was measured before and afterswelling in water overnight. No change in width was observed(see Table1.3).Setup 1Setup 2Diagram 1.1. Experimental Setups for UV Experiments124 CMDITR Review of Undergraduate Research Vol. 2 No. 1 Summer 2005