Chiral Optofluidics with a Plasmonic Metasurface Using the Photothermal Effect

Abstract

Plasmonic metasurfaces with the photothermal effect have been increasingly investigated for optofluidics. Meanwhile, along with the expanding application of circularly polarized light, a growing number of investigations on chiral plasmonic metasurfaces have been conducted. However, few studies have explored the chirality and the thermal-induced convection of such systems simultaneously. This paper aims to theoretically investigate the dynamics of the thermally induced fluid convection of a chiral plasmonic metasurface. The proposed metasurface exhibits giant circular dichroism in absorption and thus leads to a strong photothermal effect. On the basis of the multiphysical analysis, including optics, thermodynamics, and hydrodynamics, we propose a concept of chiral spectroscopy termed optofluidic circular dichroism. Our results show that different fluid velocities of thermally induced convection appear around a chiral plasmonic metasurface under different circularly polarized excitation. The chiral fluid convection is induced by an asymmetric heat distribution generated by absorbed photons in the plasmonic heater. This concept can be potentially used to induce chiral fluid convection utilizing the chiral photothermal effect. Our proposed structure can potentially be used in various optofluidics applications related to biochemistry, clinical biology, and so on.

Ultraflexible Photothermal Superhydrophobic Coating with Multifunctional Applications Based on Plasmonic TiN Nanoparticles

“…To obtain the electric field in the system, our COMSOL model solves the time‐independent electromagnetic wave equation [ 14a ] where E is the electric field, k 0 is the free space wavenumber, ε( r , ω) is the space‐ and wavelength‐dependent relative permittivity of the material, and ω is the angular frequency of the incident light. The conversion of optical energy to thermal energy can be described by Equation () [ 17 ] where T is the temperature, t is the time, and ρ, C p , and k are the density, specific heat capacity, and thermal conductivity of the considered material, respectively; furthermore, Q r is the local heat power of the TiN absorber. The generated heat power Q r can be obtained from Equation () [ 18 ] where ε 0 is the vacuum permittivity and Im{ε( r , ω)} is the imaginary part of the permittivity.…”

“…where E is the electric field, k 0 is the free space wavenumber, ε(r, ω) is the space-and wavelength-dependent relative permittivity of the material, and ω is the angular frequency of the incident light. The conversion of optical energy to thermal energy can be described by Equation ( 2) [17] • r c ρ ( )…”

Manipulation of Fluid Convection by Surface Lattice Resonance

“…With the increase of time, the water temperature rises in the two optofluidic systems: first, it increases rapidly and then gradually reaches a steady state at around 4 µs. This time‐varying temperature behavior can be explained by [ 9,48 ] $$\[ \begin{array}{*{20}{c}}{T = {T_{{\rm{amb}}}} + \frac{{IA\eta }}{B} + b{{\rm{e}}^{ - B\Delta t/c}}}\end{array} \]$$where T amb is the environment temperature, B is the thermal conductivity coefficient from water to the external environment, I and A are the incident light flux and the surface area exposed to radiation absorbance, η is the PCE of optofluidic system, and Δ t and c are the irradiation time and specific heat capacity of water. When the irradiation time is long enough, there will be e − B Δ t / c ≈ 0, the temperature will reach a steady state.…”

Real-Time Visual Sensing of Heat or Mass Transfer Processes for Microfluids via Tamm Plasmon Polaritons

“…Explorations are increasingly evolving to smaller scale and size, which makes microfluids more important in modern science and technology, such as bioscience, 29 , 30 environmental engineering, 31 food science, 32 , 33 and optofluidics. 34 Heat and mass transfer characteristics of microfluids are supertiny processes that are hard to be real-time observed. An effective method to instantaneously detect the heat and mass transfer processes is urgently necessary for microfluids.…”