Surfactant-Controlled Photothermal Assembly of Nanoparticles and Microparticles for Rapid Concentration Measurement of Microbes

Abstract

Light-induced heating on a solid–liquid interface can generate a vapor submillimeter bubble and fluid flow, which enables us to densely and rapidly assemble dispersoids into a desired position (photothermal assembly). Here, we revealed that the surface modulation of the light-induced bubble by a surfactant dominates the assembly dynamics of nanoparticles and microparticles as dispersoids, which results in highly efficient photothermal assembly under the surfactant-controlled fluid flow. This mechanism can facilitate the concentration measurement of small objects (microparticles, bacteria, viruses, etc.). Particularly, we found that the surfactant-controlled fluid flow and bubble enable high-density assembly of dispersoids and remarkable enhancement of assembly efficiency, achieving 10–20 times in comparison with the case of no surfactant. This result can extend the limit of measurable concentration by one order. Furthermore, this study revealed the influence of concentration, size, and constituent material of the dispersoids on the assembly efficiency for the improvement of measurement precision. These findings are crucial for laser-induced assembly for the rapid concentration measurement of various microbes without a cultivation process as bioanalysis, for the high-sensitivity detection of harmful particles, and for the colloidal lithography.

Laser‐Based Printing: From Liquids to Microstructures

“…(d) Reproduced with permission. [ 85 ] Copyright 2019, American Chemical Society. (e, i) Adapted with permission.…”

Sensitivity‐Enhancing Strategies in Optical Biosensing

“…[ 93–95 ] Along with surface assembly of microbes, synthetic particles, and molecules, small‐molecule sensing has been reported based on this phenomenon. [ 96–105 ] However, a high working temperature required to vaporize water has prevented the optothermally generated microbubbles from being applied to sensing proteins, whose activity is subject to thermal denaturation. [ 95,106 ] Kim et al.…”

“…[93][94][95] Along with surface assembly of microbes, synthetic particles, and molecules, small-molecule sensing has been reported based on this phenomenon. [96][97][98][99][100][101][102][103][104][105] However, a high working temperature required to vaporize water has prevented the optothermally generated microbubbles from being applied to sensing proteins, whose activity is subject to thermal denaturation. [95,106] Kim et al reported a biphasic liquid system wherein volatile, water-immiscible perfluoropentane (PFP) was emulsified into an aqueous medium as a bubble-generating liquid (Figure 5e).…”

Damage-free light-induced assembly of intestinal bacteria with a bubble-mimetic substrate

“…On the other hand, paying attention to the collective phenomenon of localized surface plasmons, the principles of light-induced acceleration of the biochemical reactions of biological nanomaterials (e.g., DNA and proteins) were realized based on the synergetic effect of light-induced force and light-induced convection due to photothermal effect 24 – 27 . In previous studies, “photothermal assembly” based on convection due to photothermal effect and the formation of a submillimeter bubble under local high-temperature conditions were used for large-scale production of organic molecular poly-crystals 28 , electrical detection of bio-nanomaterials 29 , and rapid trapping of microbes at a high density 30 , 31 . As fundamental studies, micron-sized structures have been formed by assembling nanoparticles using a laser-induced microbubble 32 , 33 , and the convection mechanism around the photothermal microbubble has been investigated in detail 34 , 35 .…”