We present a theoretical analysis and experimental demonstration of particle trapping and manipulation around optothermally generated bubbles. We show that a particle located within 500 μm of a surface bubble can be attracted towards a bubble by drag force resulting from a convective flow. Once the particle comes in contact with the bubble's surface, a balance between surface tension forces and pressure forces traps the particle on the bubble surface, allowing the particle to move with the bubble without detaching. The proposed mechanism is confirmed by computational fluid dynamics simulations, force calculations, and experiments. Based on this mechanism, we experimentally demonstrated a novel approach for manipulating microparticles via optothermally generated bubbles. Using this approach, randomly distributed microparticles were effectively collected and carried to predefined locations. Single particles were also manipulated along prescribed trajectories. This bubble-based particle trapping and manipulation technique can be useful in applications such as micro assembly, particle concentration, and high-precision particle separation.

Plasmonics provides an unparalleled method for manipulating light beyond the diffraction limit, making it a promising technology for the development of ultra-small, ultra-fast and power-efficient optical devices. To date, the majority of plasmonic devices are in the solid state and have limited tunability or configurability. Moreover, individual solid-state plasmonic devices lack the ability to deliver multiple functionalities. Here we utilize laser-induced surface bubbles on a metal film to demonstrate, for the first time, a plasmonic lens in a microfluidic environment. Our ‘plasmofluidic lens’ is dynamically tunable and reconfigurable. We record divergence, collimation and focusing of surface plasmon polaritons using this device. The plasmofluidic lens requires no sophisticated nanofabrication and utilizes only a single low-cost diode laser. Our results show that the integration of plasmonics and microfluidics allows for new opportunities in developing complex plasmonic elements with multiple functionalities, high-sensitivity and high-throughput biomedical detection systems, as well as on-chip, all-optical information processing techniques.

In this work, we develop an in situ method to grow highly controllable, sensitive, three-dimensional (3D) surface-enhanced Raman scattering (SERS) substrates via an optothermal effect within microfluidic devices. Implementing this approach, we fabricate SERS substrates composed of Ag@ZnO structures at prescribed locations inside microfluidic channels, sites within which current fabrication of SERS structures has been arduous. Conveniently, properties of the 3D Ag@ZnO nanostructures such as length, packing density, and coverage can also be adjusted by tuning laser irradiation parameters. After exploring the fabrication of the 3D nanostructures, we demonstrate a SERS enhancement factor of up to ∼2 × 10⁶ and investigate the optical properties of the 3D Ag@ZnO structures through finite-difference time-domain simulations. To illustrate the potential value of our technique, low concentrations of biomolecules in the liquid state are detected. Moreover, an integrated cell-trapping function of the 3D Ag@ZnO structures records the surface chemical fingerprint of a living cell. Overall, our optothermal-effect-based fabrication technique offers an effective combination of microfluidics with SERS, resolving problems associated with the fabrication of SERS substrates in microfluidic channels. With its advantages in functionality, simplicity, and sensitivity, the microfluidic-SERS platform presented should be valuable in many biological, biochemical, and biomedical applications.

After half a billion years of evolution, arthropods have developed sophisticated compound eyes with extraordinary visual capabilities that have inspired the development of artificial compound eyes. However, the limited 2D nature of most traditional fabrication techniques makes it challenging to directly replicate these natural systems. Here, we present a biomimetic apposition compound eye fabricated using a microfluidic-assisted 3D-printing technique. Each microlens is connected to the bottom planar surface of the eye via intracorporal, zero-crosstalk refractive-index-matched waveguides to mimic the rhabdoms of a natural eye. Full-colour wide-angle panoramic views and position tracking of a point source are realized by placing the fabricated eye directly on top of a commercial imaging sensor. As a biomimetic analogue to naturally occurring compound eyes, the eye’s full-colour 3D to 2D mapping capability has the potential to enable a wide variety of applications from improving endoscopic imaging to enhancing machine vision for facilitating human–robot interactions.

Under laser illumination, a solid-state surface or nanostructure can turn into a micro/nano heating source with the so-called optothermal effect. This effect allows for non-invasive control of heat at the micro/nanoscale. In the presence of a liquid, a surface bubble can be generated on top of the solid surface or nanostructure at a temperature much higher than the boiling point of the liquid. The high temperature and the fluid flow associated with the optothermally generated surface bubble enable many intriguing applications, ranging from the micro/nano-manipulation of fluids, particles, cells, and light to the synthesis of micro/nano-structures under ambient conditions. In this review article, we present the fundamentals, recent developments, and future perspectives in this emerging field.