Thermal Molecular Focusing: Tunable Cross Effect of Phoresis and Advection

TL;DR

This paper introduces a theoretical model demonstrating how a moving thermal spot can focus large molecules like DNA through a combination of phoresis and advection, enabling tunable control of molecular transport.

Contribution

The study develops a coupled heat conduction and viscoelastic model explaining the interplay of phoretic and hydrodynamic focusing of molecules under dynamic thermal fields.

Findings

Thermal fields can focus DNA molecules with frequency control.

The model explains the coupling of heat conduction, viscoelasticity, and viscosity gradients.

Potential application in designing miniaturized microfluidic pumps.

Abstract

The control of solute fluxes through either microscopic phoresis or hydrodynamic advection is a fundamental way to transport molecules, which are ubiquitously present in nature and technology. We study the transport of large solute such as DNA driven by a time-dependent thermal field in a polymer solution. Heat propagation of a single heat spot moving back and forth gives rise to the molecular focusing of DNA with frequency-tunable control. We developed a theoretical model, where heat conduction, viscoelastic expansion of walls, and the viscosity gradient of a smaller solute are coupled, and that can explain the underlying hydrodynamic focusing and its interplay with phoretic transports. This cross effect may allow one to design a unique miniaturized pump in microfluidics.