Sylgard 184

The Polydimethylsiloxane (PDMS) topological matrixes were performed as previously described [19] (link). The spacing between the micropillars was 4 µm; the diameter of the micropillars was 4 µm; the height of the micropillars was also 4 µm. PDMS (Sylgard 184, Dow-Corning, Midland, MI) consisting of an oligomeric base and a curing agent was thoroughly mixed at two ratios (oligomeric base/Sylgard184 = 10:1 and 30:1). The mixture was cast onto the silicon mold, degassed under vacuum for about 20 min and then cross-linked at 80°C for 12 h. Finally, the PDMS matrixes were peeled off from the silicon mold.

The fabrication of soft microfluidic channels was based on our previously reported method (28 (link)). Briefly, the soft microfluidic probe consists of a defined microchannel layer and a capping layer, which are bonded by corona treatment. The microchannel layer was formed by casting and curing a PDMS layer (elastomer/curing agent ratio, 10:1; Sylgard 184, Dow Corning) (~80 μm) between a patterned silicon wafer and a supporting glass slide. Microfluidic channel patterns on the silicon wafer were created by a standard photolithography approach, followed by deep reactive ion etching (DRIE) (STS Pegasus ICP-DRIE; SPTS Technologies, Newport, UK). Polymethyl methacrylate (PMMA) A2 solution (2 g PMMA dissolved in 98 g anisole) was spin-coated at a rate of 3000 rpm for 1 min onto the patterned silicon wafer surface and cured at 185°C for 5 min resulting in an antiadhesion layer. The capping layer (thickness, ~70 μm) was prepared by spin-casting PDMS (elastomer/curing agent ratio, 10:1; Sylgard 184, Dow Corning) on a PMMA-coated glass slide followed by baking at 70°C for 45 to 60 min. The total thickness of the channel layer and the capping layer is ~150 μm.

The microchannels and microvessels were fabricated in polydimethylsiloxane (PDMS) using soft lithography and replica molding. A layer of photoresistant SU-8 2100 (MicroChem Corp., MA, US) was patterned on a silicon wafer by photolithography, resulting in a positive relief patterns of channels and a series of relief patterns of microvessels. For channels, a prepolymer mixture of Sylgard 184 (Dow Corning, MI, US) was cast and cured against the positive relief master to obtain a negative replica-molded piece. After curing for 2 h at 70°C, the PDMS was peeled off the master, and inlets and outlets of the channel were punched with a sharpened needle. For microvessels, a spin coater (1000 rpm, 10 s) was used to cure a prepolymer mixture of Sylgard 184 (Dow Corning, MI, US) against the positive relief master to obtain a negative replica-molded membrane. After curing for 10 min at 70°C, the membrane was peeled off the master, and the upper surface that had no pattern was adhered to glass. The patterned surfaces of channels and microvessels were treated with oxygen plasma for 1 min with 50 mW, and, subsequently, the microchannel was assembled on top of the microvessels to form an integrated device. The dimensions of an individual microvessel were 72.8 ± 1.36 µm in length and 52.5 ± 0.38 in width, the filled channel kept 9.5 µl in volume in total.