Figure 1

Sol-gel-based in-situ direct laser writing (isDLW) concept. (a–g) Illustrations of the isDLW fabrication protocol for a microfluidic element printed inside a semi-ovular microchannel. (a) DLW of the channel mold structures. (b) Fabricated negative master mold. (c) Micromolding of poly(dimethylsiloxane) (PDMS). (d) Micromolded PDMS bonded to a glass substrate. (e) Acetic (Ac.) Acid-catalyzed sol-gel reaction for coating the PDMS microchannels with an adhesive layer of (3-Aminopropyl)triethoxysilane (APTES). (f) Vacuum loading of a liquid-phase photocurable material into the sol-gel-coated microchannels. (g) The “ceiling-to-floor” isDLW process. Focused femtosecond laser pulses (red) pass through an objective lens, immersion oil, glass substrate, and liquid-phase photomaterial to initiate spatially controlled photopolymerization (white) in a point-by-point, layer-by-layer methodology, ultimately producing a structure comprised of cured photomaterial (blue) that is fully sealed to the entire luminal surface of the sol-gel-coated microchannel. (h–m) Micrographs of (Top) DLW-printed negative master molds, and (Bottom) replicated PDMS profiles corresponding to distinct microchannel cross-sectional geometries: (h) rectangular (deep reactive-ion etching (DRIE) mimetic), (i) outward-tapered (positive-tone photoresist mimetic), (j) inward-tapered (negative-tone photoresist mimetic), (k) semi-circular, (l) semi-ovular, and (m) triangular (see also Supplementary Fig. S1). Scale bars = 100 μm.