A two-step strategy for delivering particles to targets hidden within microfabricated porous media

Abstract

The delivery of small particles into porous environments remains highly challenging because of the low permeability to the fluids that carry these colloids. Even more challenging is that the specific location of targets in the porous environment usually is not known and cannot be determined from the outside. Here, we demonstrate a two-step strategy to deliver suspended colloids to targets that are “hidden” within closed porous media. The first step serves to automatically convert any hidden targets into soluto-inertial “beacons,” capable of sustaining long-lived solute outfluxes. The second step introduces the deliverable objects, which are designed to autonomously migrate against the solute fluxes emitted by the targets, thereby following chemical trails that lead to the target. Experimental and theoretical demonstrations of the strategy lay out the design elements required for the solute and the deliverable objects, suggesting routes to delivering colloidal objects to hidden targets in various environments and technologies.

Diffusiophoresis, Diffusioosmosis, and Microfluidics: Surface-Flow-Driven Phenomena in the Presence of Flow

“…A dead-end pore has been used to demonstrate various transport behaviors along a one-dimensional solute gradient (Figure ). − ,,,,,− As described above, H-shaped channels with open-end pores can also generate a one-dimensional concentration gradient of solutes. In the H-channel, a steady-state concentration gradient can be set up, which generates constant diffusioosmotic velocity along the wall.…”

“…(d) Target-delivery using diffusiophoresis in a complex dead-end pore system. Reproduced with permission from ref . Copyright 2020 American Association for the Advancement of Science.…”

Temperature dependence of diffusiophoresis via a novel microfluidic approach

“…Derjaguin first discovered DP under non-electrolyte gradients, 1 and later under electrolyte gradients to explain the high rates of latex deposition during the manufacture of rubber gloves. 2,3 Since then, DP has been leveraged for varied applications including polymer deposition on metals, [4][5][6][7] particle deposition and fouling of membranes, 8,9 transport in dead-end pores, [10][11][12][13] membraneless water filtration, 14 cleaning of fibers and fabrics, 15 particle trapping and separation, [16][17][18][19][20][21][22] self-propelling active particles [23][24][25] and solutoinertial interactions. [26][27][28] Recently, DP has been explored as a means to drive migration of oil droplets out of dead-end pores 10,29 or to deliver sensing and recovery agents to hidden oil in reservoirs for enhanced oil recovery (EOR).…”

“…[26][27][28] Recently, DP has been explored as a means to drive migration of oil droplets out of dead-end pores 10,29 or to deliver sensing and recovery agents to hidden oil in reservoirs for enhanced oil recovery (EOR). 12,13,[30][31][32] When low-salinity flood water, which is passed in the reservoir to remove oil, 33 comes in contact with high-salinity connate water present with the trapped oil in dead-end pores and cracks, salinity gradients arise that can potentially drive DP migration. However, reservoir temperatures significantly exceed room temperature, and most experimental studies of DP to date have been carried out under ambient laboratory conditions.…”

“…Derjaguin first discovered DP under non-electrolyte gradients, 1 and later under electrolyte gradients to explain the high rates of latex deposition during the manufacture of rubber gloves. 2,3 Since then, DP has been leveraged for varied applications including polymer deposition on metals, 4–7 particle deposition and fouling of membranes, 8,9 transport in dead-end pores, 10–13 membraneless water filtration, 14 cleaning of fibers and fabrics, 15 particle trapping and separation, 16–22 self-propelling active particles 23–25 and soluto-inertial interactions. 26–28…”