Effect of Flow Rates on Generation of Monodisperse Clay–Poly(N-isopropylacrylamide) Embolic Microspheres Using Hydrodynamic Focusing Microfluidic Device

Abstract

Vascular embolization is a minimally invasive nonsurgical technique obstructing a blood vessel by lodgment of embolic materials to treat cancers and vascular lesions. In this paper, we have carried out a parametric study of generation of monodisperse clay-poly(N-isopropylacrylamide) (clay-PNIPAAm) embolic microspheres of which size is comparable to a blood vessel (about 400 m). To achieve monodisperse water-phase clay/ NIPAAm microdroplets, we have designed and fabricated a poly(dimethylsiloxane) (PDMS) hydrodynamic focusing microfluidic device (HFMD) for the generation of microdroplets with the affinity of continuous oil-phase fluid to the hydrophobic PDMS taken into account. We have investigated the influence of process-related flow conditions on the microdroplet generation to determine a proper processing window for obtaining monodisperse microdroplets with the fabricated HFMD. A parametric study of generation of monodisperse microdroplets was carried out by changing volumetric flow rates of two immiscible fluids within the determined processing window. For the suggested condition, the fabricated clay-PNIPAAm microspheres of about 400 m in diameter showed an extremely narrow size distribution with a coefficient of variation of 0.41%. We have also showed the floatability of the fabricated clay-PNIPAAm microspheres in saline and the smooth passage of the microspheres through a commercially available microcatheter as in vitro characterization for embolization. #

One-Step Microfluidic Synthesis of Janus Microhydrogels with Anisotropic Thermo-Responsive Behavior and Organophilic/Hydrophilic Loading Capability

“…The one-step synthesis of Janus microhydrogels was performed with a hydrodynamic focusing microfluidic device (HFMD). 24 The HFMD was fabricated using a conventional polydimethylsiloxane (PDMS) replica molding technique (details in Figure S2 of the Supporting Information). 25 The method is shown schematically in Figure 1a.…”

“…The injected two different NIPAAm monomer streams were merged and broken up into Janus NIPAAm monomer microdroplets by a continuous oil phase at the orifice of the HFMD due to capillary instability. 24 The immiscibility of the N-rich and N-poor phases solves the problem of mixing due to perturbations induced by the phase flow during the generation of the Janus microdroplets. The Janus NIPAAm monomer microdroplets were monodispersely generated at a frequency of 19.4 ± 0.55 Hz, as shown in Figure 1b.…”

“…The N-rich and N-poor phase monomer solutions were separately injected as two distinct streams into the HFMD using two syringe pumps each operating at a prescribed volumetric flow rate (KDS 270, KD Scientific). The injected two different NIPAAm monomer streams were merged and broken up into Janus NIPAAm monomer microdroplets by a continuous oil phase at the orifice of the HFMD due to capillary instability . The immiscibility of the N-rich and N-poor phases solves the problem of mixing due to perturbations induced by the continuous phase flow during the generation of the Janus microdroplets.…”

A rotationally focused flow (RFF) microfluidic biosensor by density difference for early-stage detectable diagnosis

“…For the CFD simulation, a microchannel design with 300 µm of width, 200 µm of height, and 4800 µm of length was chosen. The 200 µm height was fixed as the maximum height of microchannel fabricated by UV-lithography 41 . The 300 µm width and 4800 µm length were determined considering suitable aspect ratio (0.5–1) for the stable generation of hydrodynamic focusing 42 and exiting silicon microring chip dimensions, respectively.…”