Thermal optofluidics is an emerging field that promises to create numerous research and application opportunities in biophysics, biochemistry, and clinical biology. Innovation in plasmonic optics has led to the development of various invaluable tools in the fields of biosensing and microfluidic manipulation. The optothermal effect originates from light–matter interactions during photon–phonon conversion, which can lead to micro‐ or nanoscale inhomogeneities in the thermal distribution. This further induces a series of hydrodynamic phenomena such as natural convection, Marangoni convection, thermophoresis, the electrolyte Seebeck effect, depletion forces, and interfacial effects in colloidal particles. Light–matter interactions are particularly important for three aspects of microfluidics, namely the motion of colloidal particles, fluidic actuation, and biochemical reactions. This review first systematically elucidates the role of both nanoscale plasmonic thermal generation and heat‐induced fluidic motion in optofluidic microsystems. Then, recent state‐of‐the‐art thermal optofluidic applications of the above‐listed three aspects are presented. The paper aims to provide an insightful reference for future research in optofluidic biochemical systems.

A variety of surface plasmon resonance (SPR) sensing devices have been extensively used in biochemical detection for their characteristics of label-free, highly sensitive, and faster detecting. Among them, the spectrum-based SPR sensing devices have offered us great advantages in highthroughput sensing due to their large dynamic range and the possibility of detection resolution similar to that offered by angle interrogation. This paper demonstrates a spectrum-based SPR imaging sensing system with fast wavelength scanning capability achieved by an acousto-optic tunable filter (AOTF) and a low-cost and speckle-free halogen lamp implemented as the SPR excitation source. Especially, we developed a novel four-parameter-based spectral curve readjusting (4-PSCR) method for data processing, which offered us a faster and more accurate spectral data curve fitting process than the traditional polynomial fitting method. With the configuration, we have also conducted an SPR highthroughput detection of the novel coronavirus (COVID-19) spike protein, proving its application possibility in the screening of COVID-19 with high accuracy. We believe that the higher sensitivity and accuracy of the system have made it readily used in biochemical imaging and detecting applications.

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The resolution of fluorescence microscopy is limited by the diffraction imaging system, and many methods have been proposed to overcome the optical diffraction limit for achieving super-resolution imaging. Structured illumination microscopy (SIM) is one of the most competitive approaches and has demonstrated remarkable achievements. In the last two decades, SIM has been improved in many aspects, such as the enhancement of resolution and imaging depth and virtual modulation-based SIM. In this Perspective, we present an overview of the development of SIM, including the basic theory, application to biomedical studies, and the remarkable progress of SIM. Owing to its flexibility with respect to combination with other methods, SIM can be considered a powerful tool for biomedical study, offering augmented imaging capabilities by exploiting complementary advantages.

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Surface plasmon resonance microscopy (SPRM) has been widely employed in biological fields because of its high spatial resolution and label-free detection modality. In this study, SPRM based on total internal reflection (TIR) is studied via a home-built SPRM system, and the principle of imaging of a single nanoparticle is analyzed as well. By designing a ring filter and combining it with the deconvolution algorithm in Fourier space, the parabolic tail of the nanoparticle image is removed, in which a spatial resolution of 248 nm is obtained. In addition, we also measured the specific binding between the human IgG antigen and goat anti-human IgG antibody using the TIR-based SPRM. The experimental results have proved that the system can image sparse nanoparticles and monitor biomolecular interactions.

Phase interrogation surface plasmon resonance (SPR) imaging is, in principle, suitable in multiple samples and high-throughput detection, but the refractive index difference of various samples can be largely varied, while the dynamic range of phase interrogation SPR is narrow. So it is difficult to perform multi-sample detection in phase interrogation mode. In this paper, we successfully designed a multi-channel phase interrogation detection SPR imaging sensing scheme based on a common optical interference path between p- and s-polarized light without using any mechanical moving components. The fixed optical path difference between p- and s-polarized light is introduced by a birefringence crystal to produce sinusoidal spectral interference fringes. We adopted a time-division-multiplexing peak-finding algorithm to track the resonance wavelength so that the detection range can cover every channel. The phase values which carry the high sensitivity signal of the corresponding samples are calculated by the iterative parameter scanning cross-correlation algorithm.

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