Separation Phenomena in Tailored Micro- and Nanofluidic Environments

Abstract

Separations of bioanalytes require robust, effective, and selective migration phenomena. However, due to the complexity of biological matrices such as body fluids or tissue, these requirements are difficult to achieve. The separations field is thus constantly evolving to develop suitable methods to separate biomarkers and fractionate biospecimens for further interrogation of biomolecular content. Advances in the field of microfabrication allow the tailored generation of micro- and nanofluidic environments. These can be exploited to induce interactions and dynamics of biological species with the corresponding geometrical features, which in turn can be capitalized for novel separation approaches. This review provides an overview of several unique separation applications demonstrated in recent years in tailored micro- and nanofluidic environments. These include electrokinetic methods such as dielectrophoresis and electrophoresis, but also rather nonintuitive ratchet separation mechanisms, continuous flow separations, and fractionations such as deterministic lateral displacement, as well as methods employing entropic forces for separation.

Tunable Mass Separation via Negative Mobility

“…For such a broad (sub)micrometer scale, efficient isolation techniques are required to allow tunability of the particle size intended for separation. Unluckily, the latter are rather scarce [9,10], however, recently some progress has been made in this direction [11][12][13] In this work we aspire to partially fill this significant know-how gap by demonstrating a nonintuitive, yet efficient separation strategy taking advantage of a paradoxical mechanism of negative mobility [14][15][16][17]. We show that under the action of a static bias only particles of a given linear size move in the direction opposite to this net force whereas the others migrate concurrently towards it.…”

“…It is because in many realistic setups it is implemented via the constant external field, e.g. in the microfludic experiments in the form of a spatially uniform electric field which induces the particle electrophoresis [10]. In most cases its intensity can be changed relatively easily, as opposed to the frequency ω of the external harmonic driving which often requires complete rebuilding of the experimental setup.…”

Carbon nanotube dielectrophoresis: Theory and applications

“…To manipulate CNTs with DEP, one needs to introduce high electric fields and gradients in the microfluidic device which can be introduced with the fabrication of microelectrodes or with insulating geometries. With advances in microfabrication techniques, two major techniques have been adopted to generate such high electric fields and gradients for dielectrophoretic manipulation of CNTs [30,147,148]. The first approach is called electrode‐based DEP (eDEP), which was introduced by Pohl et al.…”

Temperature-Induced Tunable Particle Separation

“…Unfortunately, bioparticles span a large size range comprising several orders of magnitude starting from hundreds of nanometers to tens of micrometers [7,8]. For such sub-micro scale thermal fluctuations are lead actors and isolation techniques are rather scarce [9,10]. An ideal solution would be a tunable method which allows to change a bioparticle size targeted for separation by controlling one of its parameters.…”

“…Our setup can be experimentally realized using a labon-a-chip device consisting of microfluidic structure. The oscillating force driving the system out of equilibrium may be induced through hydrodynamic flow, but electrophoresis, electroosmosis or dielectrophoresis can also be utilized [10]. In particular, the proof of principle experiment of a similar separation scheme has been already performed with insulator dielectrophoresis in a nonlinear, symmetric microfluidic structure with electrokinetically activated transport [15,16].…”