Vls 3

Filter holders for two common mobile phones (Google Nexus 5X and LG Pixel 2) were designed by layering 1/16″ (1.59 mm) and 1/8″ (3.18 mm) thick poly(methyl methacrylate) (PMMA) sheets (McMaster-Carr) that were laser cut (VLS 3.60, Universal Laser Systems), assembled, and then chemically welded with dichloromethane. The filter holder design was engineered to minimize light leakage (including autofluorescence) with contours corresponding to the phones’ profiles. Cutouts over the camera aperture and the camera flash LED hold the dual-bandpass 479/585 nm excitation (Semrock FF01–479/585–12.5) and 524/628 nm emission filters (Semrock FF01–524/628–12.5) for fluorescein and Texas Red, respectively. The excitation light is partially collimated with a 12 mm wide, 12 mm focal length plano-convex lens (Edmund Optics 45–083) placed 6 mm from the LED.

Each flow cell, consisting of two parallel rectangular profile flow channels, was manufactured by placing a silicone gasket (Medical Grade, 0.007″, BioPlexus, Ventura, CA, USA) between a plasma-cleaned microscope slide (VWR International, Radnor, PA, USA) and a Nexterion-H slide (Schott, Tempe, AZ, USA) (Fig 1). Flow channel features were patterned on the silicone gasket using a laser cutter (VLS3.60, Universal Laser Systems, Scottsdale, AZ, USA). Flow channel dimensions were 1 mm wide, 0.18 mm high, and 70 mm long. Each flow channel contained an upstream stenotic region and a downstream capture region. Stenotic regions were 10 mm in length. Capture regions were 25 mm downstream from the end of the stenotic regions. The width of stenotic regions was varied from 1.0 mm to 0.2 mm to create five different stenosis levels, from 0 to 80% stenosis defined as:
$$\text{Stenosis}(\%)=\frac{\left(W_{inlet}-W_{stenosis}\right)}{W_{inlet}}\times 100$$
where w_inlet was the width of inlet of the flow channels (1 mm) and w_stenosis was the width of the stenotic regions. Control flow channel, a representative of small artery, did not contain any upstream stenotic region (0% stenosis). Wall shear strain rates were calculated at a constant volumetric flow rate by generating a three-dimensional model of each flow channel in COMSOL Multiphysics (COMSOL, Inc., Burlington, MA, USA).