@article{hsu14a,
 abstract = {The simultaneous concentration gradient focusing and separation of proteins in a silica nanofluidic channel of various geometries is investigated experimentally and theoretically. Previous modelling of a similar device [Inglis et al.{,} Angew. Chem. Int. Ed.{,} 2011{,} 50{,} 7546] assumed a uniform velocity profile along the length of the nanochannel. Using detailed numerical analysis incorporating charge regulation and viscoelectric effects{,} we show that in reality the varying electric double layer thickness and nanochannel surface charge density{,} caused by the concentration gradient{,} induce a highly non-uniform velocity profile{,} fundamentally altering the protein trapping mechanism: The direction of the local electroosmotic flow reverses and two local vortices are formed near the centreline of the nanochannel at the low salt concentration end{,} enhancing trapping efficiency. The simulation results for yellow/red fluorescent protein R-PE concentration enhancement{,} peak focusing position and peak focusing width are in good agreement with the experimental measurements{,} validating the model. The predicted separation of yellow/red (R-PE) from green (Dyl-Strep) fluorescent proteins is close to that from a previous experiment [Inglis et al.{,} Angew. Chem. Int. Ed.{,} 2011{,} 50{,} 7546] conducted in a slightly different geometry. The results will inform the design of new class of matrix-free particle focusing and separation devices.},
 author = {Hsu, Wei-Lun and Harvie, Dalton J.E. and Davidson, Malcolm R. and Jeong, Helen and Goldys, Ewa M. and Inglis, David},
 doi = {10.1039/C4LC00504J},
 journal = {Lab Chip},
 keywords = {electrokinetic; arb},
 pages = {3539-3549},
 publisher = {The Royal Society of Chemistry},
 title = {Concentration gradient focusing and separation in a silica nanofluidic channel with a non-uniform electroosmotic flow},
 url = {http://dx.doi.org/10.1039/C4LC00504J},
 volume = {14},
 year = {2014},
}