(483b) Dual Hydrodynamic Trap

Recent advancements in science and engineering have enabled trapping and manipulation of individual particles and macromolecules within an aqueous medium using a flow-based confinement method [1-3]. Here, we demonstrate a dual hydrodynamic trap, simultaneous contact-free trapping of two particles using fluid flow. Through Brownian dynamics simulations, we demonstrate that two particles/macromolecules can be confined and manipulated at the stagnation point of planar extensional flows coupled in series.

The dual hydrodynamic trap is realized by generating planar extensional flows through two opposing laminar streams meeting at a four-way microchannel junction and exiting in the perpendicular direction. An exit channel on one of the junctions is annexed to the inlet of the another, thereby creating two coupled planar extensional flows. We previously showed that one of these planar extensional flows can be manipulated via active feedback control to confine a micro/nanoscale particle at the stagnation point [2-3]. For dual hydrodynamic trap, we employ active feedback control for both junctions yielding simultaneous particle confinement.

We derived analytical expressions for stagnation point positions at each junction as a function of flow rates and channel width. These expressions formed the basis of implementing a proportional feedback control system which enabled active particle trapping at each junction. For dual hydrodynamic trap, the feedback control mechanism is inherently implemented in orthogonal directions at each junction, thereby allowing active independent control of trapped particle pairs. However, since the flows are coupled, we determined the extent to which manipulation of one stagnation point changes the position of the other in the direction of passive confinement.

Furthermore, we analyzed the impact of incoming flow rates on particle confinement. In addition, we measured the effect of feedback control parameters and particle size on particle confinement. Overall, we demonstrate the feasibility of simultaneous confinement and manipulation of micro and nanoscale particles in free solution using coupled planar extensional flows. We will discuss the advantages of our dual hydrodynamic trap and highlight some of its applications in polymer science, specifically, trapping and stretching a linear polymer tethered to a micro/nanoparticle at each end. Our study demonstrates the versatility of flow-based confinement and furthers our understanding of feedback-controlled particle manipulation.

1. "Stokes trap for multiplexed particle manipulation and assembly using fluidics", A Shenoy, CV Rao, CM Schroeder, Proceedings of the National Academy of Sciences 113 (15), 3976-3981 (2016)

2. "Manipulation and confinement of single particles using fluid flow", M Tanyeri, CM Schroeder, Nano Letters 13 (6), 2357-2364 (2013)

3. "A microfluidic-based hydrodynamic trap: design and implementation", M Tanyeri, M Ranka, N Sittipolkul, CM Schroeder, Lab on a Chip 11 (10), 1786-1794 (2011)