Energy Conversion Efficiency of Nanofluidic Batteries: Hydrodynamic Slip and Access Resistance

Abstract

With asymptotic and numerical analyses, we systematically study the influence of slip length and access Ohmic resistance (due to pore-end field focusing and concentration polarization) on the energy conversion efficiency of pressure-driven electrolyte flow through a charged nanopore. Hydrodynamic slip reduces the percent of energy dissipated by viscous dissipation but, through electro-osmotic convective current, can also reduce the electrical resistance of the nanopore. Since the nanopore resistance is in parallel to the load-access serial resistance, the latter effect can actually reduce useful current through the load. These two opposing effects of slip produce specific and finite optimum values of surface charge density and ionic strength. The optimization offers explicit analytical estimates for the realistic parameters and suggests an upper bound of 50% conversion efficiency at the slip length of 90 nm and 35% for measured electro-osmotic flow slip lengths of about 30 nm for charged channels.

Future microfluidic and nanofluidic modular platforms for nucleic acid liquid biopsy in precision medicine

“…181 Instrumentation should ideally be also reconfigurable so that it can easily accommodate the integrated modular platform. 134,135,173 Future precision medicine will heavily depend on the ability to perform frequent liquid biopsies, and in general, on profiling various nucleic acids in serum and other physiological samples for screening, diagnostic, and prognostic applications in cancer and other diseases. However, broad availability of this future molecular medical approach requires new nucleic acid diagnostic technologies quite distinct from current ones.…”

“…There are several low-cost nanopore fabrication technologies for making single and multiple solid-state nanopore membranes (see, for example, laser-assisted pulling and ion-track fabrication technologies that we have employed [134][135][136][137][138] ). Among these, track etching of polyethylene terephthalate (PET) polymer membranes and chemical etching can produce solid-state conic nanopores with very small tip diameters ranging from 5 to 10 nm.…”

“…[147][148][149][150][151][152] For example, we can pack 25 nm to 100 nm oligo-functionalized Au, silica and polystyrene NPs into iontrack etched polyethylene terephthalate (PET) polymer conic nanopores, 134,135 and into conic silica nanocapillaries pulled by laser assisted drawing. 130,136,137 We have studied the NP assembly mechanism with two-dimensional nano-wedge models fabricated by focused ion beam milling.…”

“…A more rigorous theory can be found in our theoretical work. 134,135,154 Since the focusing field in this conical geometry scales as R À2 , ion flux cannot be continuous and ion accumulation/depletion ensures to maintain local neutrality. With an applied positive voltage, the large longitudinal ionic strength and conductivity gradients increase the intra-pore ionic strength by a factor as high as 10 to beyond 1 M. In fact, such intra-pore enrichment and its depletion counterpart at negative bias are responsible for the ion current rectification observed in conic pores and wedge-shaped channels at low voltage.…”

“…134,135,173 ALD can be used to tune nanopore tip diameters from 5 nm to 100 nm, and to prolong translocation times by reversible adsorption due high-permittivity alumina layer van der Waals (vdW) forces at the smaller tips (Fig. 7).…”