Hydrodynamic Trap for Single Cells and Micro- and Nanoparticles

Abstract

Over the past twenty-five years, a diverse set of particle trapping and micromanipulation techniques have been developed to elucidate biological and biophysical mechanisms of proteins, nucleic acids, enzymes and cells. Many of the existing trapping methods rely on optical, magnetic or electric fields which are potentially perturbative to biological function. In this work, we present a novel flow-based confinement and manipulation method called the “hydrodynamic trap” which is based solely on hydrodynamic forces generated in a microfluidic device. The hydrodynamic trap is a non-contact confinement technique based on a stagnation point flow created at the junction of two perpendicular microchannels. In this way, the hydrodynamic trap enables free-solution trapping, manipulation, stretching and sorting of objects ranging from single molecules to individual cells. We successfully demonstrate trapping of single micro- and nanoscale particles (as small as 100 nm), single DNA molecules, and single cells for extended time scales with high resolution (within 1 μm for micron-sized particles) [1]. Trap stiffness was determined to be in the range κ=10−4 -10−3 pN/nm, which compares favorably to magnetic and electrophoretic tweezers. Hydrodynamic trapping is feasible for any particle with no specific requirements on the material composition or the chemical/physical nature (optical, magnetic, surface charge) of the trapped object. The hydrodynamic trap inherently enables confinement of a single target object in dilute or concentrated particle or cell suspensions, due to the semi-stable nature of trapping potential. In summary, the hydrodynamic trap provides a new platform for observation of molecules, cells and particles without surface immobilization and offers the ability to vary the surrounding medium conditions of the trapped object in real-time.[1] M. Tanyeri, E. M. Johnson-Chavarria, and C. M. Schroeder, “Hydrodynamic Trap for Single Particles and Cells” Applied Physics Letters, 2010, 96(22).