Light mineral oil

Microfluidic devices were operated semi-automatically using 21 solenoid actuators (Fluidigm Corp.) connected to a digital input-output card (NI PCI-DIO-32HS, NI PCI-6512, SCB-100, National Instruments) controlled using custom LabView (National Instruments) software. Teflon tubing fastened to 20-gauge hollow stainless steel pins (Small Parts Inc.), or gel-loading pipet tips were used to connect the chip to external pressure sources. Valves were operated at a pressure of 45 PSI, reagents were injected using 5 PSI, and cells were loaded at 1–2 PSI. Krytox 102 (DuPont) oil was used in the control lines isolating the qPCR detection chambers and water was used in the rest.
Lysis, reverse transcription, and pre-amplification thermal incubations were performed on a flatbed thermocycler block (Bio-Rad DNA Engine PTC-200; MJ Research/Bio-Rad) with light mineral oil (Fisher Scientific) added between the block and the glass slide.
Microfluidic quantitative PCR was performed on a prototype version of the BioMark Instrument, (Fluidigm) [12 (link)] with the following fluorescence imaging capabilities. Image resolution and bit depth: 4 megapixel, 16 bit. Filters: FAM: Ex 485/20 Em 525/25; VIC: Ex 530/20 Em 570/30; ROX: Ex 580/25 Em 610/15; QAS: Ex 580/25 Em 680/25. Light Source: 175 W xenon arc bulb.

De-ionized water was used as the base fluid for dispersing the nanoparticles, as well as the formation liquid for all the experiments. Laboratory grade sodium chloride purchased from Sigma Aldrich was used to make the brine solutions. The density of the brine was measured at 1000 ± 0.01 g/cm³, pH 6.46 ± 0.3, and the dynamic viscosity 0.87 ± 0.01 mPa·s at 25 °C. The oil phase was a light mineral oil from Fisher Scientific with a density of 0.84 g/cm³ and a dynamic viscosity of 39.95 mPa ± 0.11 mPa·s at 25 °C. Silica nanoparticles with a diameter of 80 nm were purchased from get nanomaterials and were used for all experiments. The sand used was a fine building sand purchased from Wickes with an average grain size between 2–4 mm.

PEG microgels were fabricated via submerged electrospraying^{79 (link),80 (link)}. Briefly, PEGaNB, KCGPQGIAGQCK, CGRGDS and LAP were dissolved in endotoxin free and sterile PBS. Precursor solutions were mixed together at a 10 wt% working concentration of PEGaNB, 0.75:1 thiol-ene molar ratio, and 1 mM and 10 mM working concentration of CGRGDS and LAP, respectively. Pre-polymer solution was electrosprayed (12 mL/h, 4.0 kV, 22-gauge needle, 16 mm tip-to-ring distance) into light mineral oil (Fisher Scientific) with Span-80 (0.05 wt%) and photopolymerized with a 365 nm light at 60 mW/cm². Microgels were isolated and washed twice in sterile PBS, once in 70% ethanol, and twice in sterile PBS. Microgels were briefly vortexed and centrifuged at 3000 × g for 15 min in between each washing step. Microgel diameter was measured using the line tool on ImageJ.