Figure 3: Optimization of residence timescale.
From: Non-polydimethylsiloxane devices for oxygen-free flow lithography
(a) Experimental set-up for measurement of diffusion coefficient of PEGDA 575 in PEG 200 in a PDMS device. The green stream consists of PEG 200 90% (v/v), PI 5% (v/v), food colouring 4% (v/v), and rhodamine acrylate 1% (v/v), while the grey stream is consisted of PEGDA 575 94% (v/v), PI 5% (v/v), and rhodamine acrylate 1% (v/v). 'T'-shaped exposure mask was used to determine the penetration depth (δ) of PEGDA. (b) Fluorescence images of particles produced with various residence times. (c) Penetration depth as a function of residence time. (d) Variation of PEGDA 575 loading percentage to determine critical gel point (∼15% monomer concentration). Synthesis was performed in PDMS devices, and all streams contained rhodamine acrylate for visualization of particle interfaces. (e) Diffusion model for determination of time, t0, at which critical gel point front reaches walls of gas-impermeable device and induces particle sticking. Simulation solution indicates the maximum residence time is 5.1 s for the creation of particles at Hm=20 μm. Scale bars, (b) 50 μm and (d) 40 μm.
