Figure 7.

Example microfluidic devices. (a) Schematic of the operation of an H-filter. Diffusion dominates mass exchange between parallel streams, enabling size fractioning via flow splitting. (b) PMMA microfluidic H-filter fabricated by laser ablation and capillarity-assisted adhesive bonding. Coin (5 pence) for comparison. (c) Operation of the PMMA H-filter under laminar flow. The bottom stream (sample inlet) contains a blue dye and 20 µm polystyrene beads. The sample and buffer streams remain parallel and split at the outlet, with a fraction of the dye that has diffused to the buffer stream exiting through the analyte outlet. Scale bar: 500 μm. (d) Percentage of the dye and beads contents recovered at the analyte outlet of the H filter at different flow rates (5, 10 and 15 ml hr⁻¹ ). Data analysed by two-way mixed ANOVA (*p < 0.05, **p < 0.01 and ns non-significant) with Bonferroni post-test and shown as mean ± s.e.m. (e) Schematic of the droplet generation process in the T-junction. The interaction between the two immiscible phases causes necking and pinching of the dispersed phase and release into the main channel. (f) PMMA T-junction droplet generator with glued tubing. Coin (5 pence) for comparison. (g) Formation and necking of a water-in-oil droplet at the T junction via dripping regime. Scale bar: 500 µm. (h) Mean droplet diameter and polydispersity index (PDI) for the droplets produced in the T-junction droplet generator at different flow rates: 0.2, 0.5 and 1 ml hr⁻¹ (flow rate ratio between continuous and disperse phases Q_C/Q_D  = 1.63 in all cases). Droplet diameter data analysed by one-way ANOVA (***p < 0.001) with Tukey post-hoc test, and shown as mean ± SD.