Direction control of quasi-stokeslet induced by thermoplasmonic heating of a water vapor microbubble

Generation of Ultralong Liposome Tubes by Membrane Fusion beneath a Laser-Induced Microbubble on Gold Surfaces

Membrane fusion (MF) is one of the most important and ubiquitous processes in living organisms. In this study, we developed a novel method for MF of liposomes. Our method is based on laser-induced bubble generation on gold surfaces (a plasmonic nanostructure or a flat film). It is a simple and quick process that takes about 1 min. Upon bubble generation, liposomes not only collect and become trapped but also fuse to form long tubes beneath the bubble. Moreover, during laser irradiation, these long tubes remain stable and move with a waving motion while continuing to grow, resulting in the creation of ultralong tubes with lengths of about 50 μm. It should be noted that the morphology of these ultralong tubes is analogous to that of a sea anemone. The behavior of the tubes was also monitored by fluorescence microscopy. The generation of these ultralong tubes is discussed on the basis of Marangoni convection and thermophoresis.

Water droplet bouncing on a non-superhydrophobic Si nanospring array

Self-cleaning surfaces often make use of superhydrophobic coatings that repel water. Here, we report a hydrophobic Si nanospring surface that effectively suppresses wetting by repelling water droplets. The dynamic response of Si nanospring arrays fabricated by glancing-angle deposition is investigated. These hydrophobic arrays of vertically standing nanosprings (about 250 nm high and 60 nm apart) allow the droplets to rebound within a few milliseconds after contact. Amazingly, the morphology of the nanostructures influences the impact dynamics. The rebound time and coefficient of restitution are higher for Si nanosprings than for vertical Si columns. By considering the droplet/nanospring surface as a coupled-spring system, we argue that the restoring force of the nanosprings may be responsible for the water-droplet rebound. The bouncing phenomena studied here are essential in the design of self-cleaning surfaces and are also of fundamental importance for the study of wetting behavior on nanostructures.

Directed Self-Assembly Driven Mesoscale Lithography Using Laser-Induced and Manipulated Microbubbles: Complex Architectures and Diverse Applications

A microbubble nucleated due to the absorption of a tightly focused laser at the interface of a liquid-solid substrate enables directed and irreversible self-assembly of mesoscopic particles dispersed in the liquid at the bubble base. This phenomenon has facilitated a new microlithography technique which has grown rapidly over the past decade and can now reliably pattern a vast range of soft materials and colloids, ranging from polymers to metals to proteins. In this review, we discuss the science behind this technology and the present state-of-the-art. Thus, we describe the physics of the self-assembly driven by the bubble, the techniques for generating complex mesoarchitectures, both discrete and continuous, and their properties, and the various applications demonstrated in plastic electronics, site-specific catalysis, and biosensing. Finally, we describe a roadmap for the technique to achieve its potential of successfully patterning "everything" mesoscopic and the challenges that lie therein.

Applications and challenges of thermoplasmonics

Over the past two decades, there has been a growing interest in the use of plasmonic nanoparticles as sources of heat remotely controlled by light, giving rise to the field of thermoplasmonics. The ability to release heat on the nanoscale has already impacted a broad range of research activities, from biomedicine to imaging and catalysis. Thermoplasmonics is now entering an important phase: some applications have engaged in an industrial stage, while others, originally full of promise, experience some difficulty in reaching their potential. Meanwhile, innovative fundamental areas of research are being developed. In this Review, we scrutinize the current research landscape in thermoplasmonics, with a specific focus on its applications and main challenges in many different fields of science, including nanomedicine, cell biology, photothermal and hot-electron chemistry, solar light harvesting, soft matter and nanofluidics.

Different Regimes of Opto-fluidics for Biological Manipulation

Metallic structures can be used for the localized heating of fluid and the controlled generation of microfluidic currents. Carefully designed currents can move and trap small particles and cells. Here we demonstrate a new bi-metallic substrate that allows much more powerful micro-scale manipulation. We show that there are multiple regimes of opto-fluidic manipulation that can be controlled by an external laser power. While the lowest power does not affect even small objects, medium power can be used for efficiently capturing and trapping particles and cells. Finally, the high-power regime can be used for 3D levitation that, for the first time, has been demonstrated in this paper. Additionally, we demonstrate opto-fluidic manipulation for an extraordinarily dynamic range of masses extending eight orders of magnitude: from 80 fg nano-wires to 5.4 µg live worms.

Ultrafast Modulation of Thermoplasmonic Nanobubbles in Water

Thermo-optically generated bubbles in water provide a powerful means for active matter control in microfluidic environments. These bubbles are often formed via continuous-wave illumination of an absorbing medium resulting in bubble nucleation via vaporization of water and subsequent bubble growth from the inward diffusion of gas molecules. However, to date, such bubbles tend to be several microns in diameter, resulting in slow dissipation. This limits the dynamic rate, spatial precision, and throughput of operation in any application. Here we show that isolated plasmonic structures can be utilized as highly localized heating elements to generate thermoplasmonic nanobubbles that can be modulated at frequencies up to several kilohertz in water, orders of magnitude faster than previously demonstrated for microbubbles. The nanobubbles are envisioned as advantageous localized active manipulation elements for high throughput microfluidic applications.