Pressure-Driven Filling of Closed-End Microchannel: Realization of Comb-Shaped Transducers for Acoustofluidics

We demonstrate the complete filling of both deionized water (DI water) and liquid metal (eutectic gallium-indium, EGaIn) into closed-end microchannels driven by a constant pressure at the inlet. A mathematical model based on gas diffusion through a porous polydimethylsiloxane (PDMS) wall is developed to unveil the physical mechanism in the filling process. The proposed theoretical analysis based on our model agrees well with the experimental observations. We also successfully generate traveling surface acoustic waves by actuating interdigitated microchannels filled with EGaIn. Our work provides significant insights into the fabrication of liquid electrodes that can be used for various acustofluidics applicationsAustralian Research Council DE170100600National Natural Science Foundation of China Grants No. 11472094, No. 11772259, No. U1613227, No. B1703

Iridium(III) complex-based activatable probe for phosphorescent/time-gated luminescent sensing and imaging of cysteine in mitochondria of live cells and animals

This study reports an activatable iridium(III) complex probe for phosphorescence/time-gated luminescence detection of cysteine (Cys) in vitro and in vivo. The probe, [Ir(ppy)2(NTY-bpy)](PF6), is developed by incorporating a strong electron withdrawing group, nitroolefin, into a bipyridine ligand of the Ir(III) complex. The luminescence of the probe is quenched due to the intramolecular charge transfer (ICT) process, but switched on by a specific recognition reaction between the probe and Cys. [Ir(ppy)2(NTY-bpy)](PF6) shows high sensitivity and selectivity for Cys detection and good biocompatibility. The long-lived emission of [Ir(ppy)2(NTY-bpy)](PF6) allows time-gated luminescence analysis of Cys in cells and human sera. These properties make it convenient for the phosphorescence and time-gated luminescence imaging and flow cytometry analysis of Cys in live samples. The Cys images in cancer cells and inflamed macrophage cells reveal that [Ir(ppy)2(NTY-bpy)](PF6) is distributed in mitochondria after cellular internalization. Visualizations and flow cytometry analysis of mitochondrial Cys levels and Cys-mediated redox activities of live cells are achieved. Using [Ir(ppy)2(NTY-bpy)](PF6) as a probe, in vivo sensing and imaging of Cys in D. magna, zebrafish, and mice are then demonstrated

Iridium(III) complex-based activatable probe for phosphorescent/time-gated luminescent sensing and imaging of cysteine in mitochondria of live cells and animals

This study reports an activatable iridium(III) complex probe for phosphorescence/time-gated luminescence detection of cysteine (Cys) in vitro and in vivo. The probe, [Ir(ppy)2(NTY-bpy)](PF6), is developed by incorporating a strong electron withdrawing group, nitroolefin, into a bipyridine ligand of the Ir(III) complex. The luminescence of the probe is quenched due to the intramolecular charge transfer (ICT) process, but switched on by a specific recognition reaction between the probe and Cys. [Ir(ppy)2(NTY-bpy)](PF6) shows high sensitivity and selectivity for Cys detection and good biocompatibility. The long-lived emission of [Ir(ppy)2(NTY-bpy)](PF6) allows time-gated luminescence analysis of Cys in cells and human sera. These properties make it convenient for the phosphorescence and time-gated luminescence imaging and flow cytometry analysis of Cys in live samples. The Cys images in cancer cells and inflamed macrophage cells reveal that [Ir(ppy)2(NTY-bpy)](PF6) is distributed in mitochondria after cellular internalization. Visualizations and flow cytometry analysis of mitochondrial Cys levels and Cys-mediated redox activities of live cells are achieved. Using [Ir(ppy)2(NTY-bpy)](PF6) as a probe, in vivo sensing and imaging of Cys in D. magna, zebrafish, and mice are then demonstrated

Thiamine pyrophosphokinase deficiency: report of two Chinese cases and a literature review

Thiamine pyrophosphokinase (TPK) deficiency, is a rare autosomal recessive disorder of congenital metabolic dysfunction caused by variants in the TPK1 gene. TPK1 variants can lead to thiamine metabolic pathway obstacles, and its clinical manifestations are highly variable. We describe two cases of TPK deficiency with completely different phenotypes and different therapeutic effects, and 26 cases of previously reported were retrospectively reviewed to improve our understanding of the clinical and genetic features of the disease. Patients with TPK deficiency present with ataxia, dysarthria, dystonia, disturbance of consciousness, seizures, and other nervous system dysfunction. Different gene variant sites may lead to different clinical features and therapeutic effects. Gene analysis is important for the diagnosis of TPK deficiency caused by TPK1 variants, and thiamine supplementation has been the mainstay of treatment for TPK deficiency to date

Investigation of micro-optofluidic components and their applications

The field of optofluidics is a combination of optics and microfluidics to generate new functionalities and to improve the integration level of optical components. Liquid replacing, liquid refractive index control and interface control are the three main methods to make reconfigurable optofluidic components. This thesis focuses on the manipulation of the interface between different flows through hydrodynamic spreading to develop tunable in-plane optofluidic components. A circular chamber is used to hydrodynamically develop the optofluidic lenses with liquid core liquid cladding (L2) structure. The two-dimensional dipole flow theory and the hydrodynamic spreading theory are applied to describe single-fluid and two-fluid models respectively. The model described here provides a method to configure optofluidic lenses with a mathematically pre-defined curvature, whose interface is atomically smooth. Furthermore, the curvature of the interface as well as the focal length can be tuned by adjusting the flow rate ratio. An optofluidic bi-concave lens, which can both focus and diverge the light, is first proposed and demonstrated. In the focusing mode of the optofluidic concave lens, a liquid with low refractive index is used as the core stream and a liquid with higher refractive index serves as the cladding stream. An auxiliary cladding liquid with a very low flow rate and a refractive index matching that of polydimethylsiloxane (PDMS) is introduced to prevent the light scattering. The light emitted from an optical fibre can be focused and the focal length can be tuned by adjusting the flow rate ratio between the core and the cladding streams. If the core inlet is blocked, the liquid from cladding inlets will converge into a new core stream and the liquid from the auxiliary cladding inlet will serve as cladding streams. Therefore, the device can seamlessly switch from the focusing mode to diverging mode. In the diverging mode, a liquid with high refractive index works as the core stream, and a liquid with refractive index matching PDMS is used as cladding streams. Owing to the higher refractive index of the core stream and the tuneable lens interface, the divergence of the light beam can be expanded and adjusted. Combining the performance of focusing and diverging, the device can greatly enhance the tunability of the focal length of an optofluidic lens. Based on the L2 structure, an optofluidic prism is developed to manipulate the in-plane light beam. This tunable micro optofluidic prism is hydrodynamically formed by one core and two cladding streams inside a sector-shape chamber. Liquid with a higher refractive index is employed as the core stream, which forms the geometry of a triangular prism. Liquid with a lower refractive index serves as cladding streams. Due to the higher refractive index of the core stream, this configuration acts as a prism. The apex angle of this optofluidic prism can be tuned by adjusting the flow rate ratio between core and cladding streams, and therefore the deviation angle of an incident light beam can be changed accordingly. Since the propagation direction of refracted light beam can be accurately controlled by choosing a proper flow rate ratio, this tunable prism can continuously scan the light beam, and therefore can be engaged in the alignment of optical path, or in the development of optical switches. Aperture stop or entrance pupil is an important optical component in imaging and detection systems. The component determines the amount of light passing through the optical system as well as the angular aperture on the object side. A tunable optofluidic aperture stop, which can be dynamically re-configured according to the flow condition, is proposed and demonstrated. A liquid core liquid cladding structure was used to form this aperture. The core liquid is optically transparent allowing light rays to pass through, while the ink with negligible optical transmittance (~ 0%) works as the cladding liquid blocking the propagation of light. When the aperture is tuned with a given flow rate ratio, the amount of light which reaches the image space as well as the angular aperture on the image side can be adjusted accordingly. Due to the solid-based lens interfaces, previous optofluidic flow cytometer designs suffer from light scattering, which degrades the quality of the focused light beam. Divergence or scattering of the light beam results in a larger beam width. One obvious disadvantage resulting from the large beam width is that the cytometer would miscount if multiple particles enter the large illumination area because the multiple particles would give only one burst in the collected signal. Normally this burst owing to multiple particles has a larger peak value than that of one particle. Thus the other consequent problem is that this burst of the signal would be misleading as it would be wrongly interpreted as a larger particle. A new design of a microfluidic flow cytometer with an optofluidic lens formed in a circular chamber is proposed and tested. The optofluidic lens has a mathematically predictable focal length, and is immune to light scattering. A well-focused light beam is achieved with a much smaller beam width of 23 um compared to all previous flow cytometers. This flow cytometer presents a good performance on particle counting, and the signal intensity shows small aberrations and strong dependence on the particle size.DOCTOR OF PHILOSOPHY (MAE

A Perspective on the Rise of Optofluidics and the Future

In the recent past, the field of optofluidics has thrived from the immense efforts of researchers from diverse communities. The concept of optofluidics combines optics and microfluidics to exploit novel properties and functionalities. In the very beginning, the unique properties of liquid, such as mobility, fungibility and deformability, initiated the motivation to develop optical elements or functions using fluid interfaces. Later on, the advancements of microelectromechanical system (MEMS) and microfluidic technologies enabled the realization of optofluidic components through the precise manipulation of fluids at microscale thus making it possible to streamline complex fabrication processes. The optofluidic system aims to fully integrate optical functions on a single chip instead of using external bulky optics, which can consequently lower the cost of system, downsize the system and make it promising for point-of-care diagnosis. This perspective gives an overview of the recent developments in the field of optofluidics. Firstly, the fundamental optofluidic components will be discussed and are categorized according to their basic working mechanisms, followed by the discussions on the functional instrumentations of the optofluidic components, as well as the current commercialization aspects of optofluidics. The paper concludes with the critical challenges that might hamper the transformation of optofluidic technologies from lab-based procedures to practical usages and commercialization

Application of Noise Detection Using Confidence Learning in Lightweight Expression Recognition System

Facial expression is an important carrier to reflect psychological emotion, and the lightweight expression recognition system with small-scale and high transportability is the basis of emotional interaction technology of intelligent robots. With the rapid development of deep learning, fine-grained expression classification based on the convolutional neural network has strong data-driven properties, and the quality of data has an important impact on the performance of the model. To solve the problem that the model has a strong dependence on the training dataset and weak generalization performance in real environments in a lightweight expression recognition system, an application method of confidence learning is proposed. The method modifies self-confidence and introduces two hyper-parameters to adjust the noise of the facial expression datasets. A lightweight model structure combining a deep separation convolution network and attention mechanism is adopted for noise detection and expression recognition. The effectiveness of dynamic noise detection is verified on datasets with different noise ratios. Optimization and model training is carried out on four public expression datasets, and the accuracy is improved by 4.41% on average in multiple test sample sets. A lightweight expression recognition system is developed, and the accuracy is significantly improved, which verifies the effectiveness of the application method

Optical alignment of a cylindrical object

This paper reports the use of theory of geometrical optics to analyze how an optical field interacts with a cylindrical object. Of great interest is the mechanism with which a laser beam with a special profile manipulates a particle which has a similar shape as the beam profile. The present paper investigates the interaction between a cylinder-shape fiber and a laser beam with a line-shape profile. Based on the Fresnel equation, a numerical model was formulated to describe the optical torque generated by a projected line-shape optical image. The drag force was also considered in the model to accurately describe the fiber's movement in a liquid. A differential equation is established to describe this damped movement of the cylinder. Parametric analysis was carried out to investigate the influence of the beam power and the liquid viscosity as well as the density, the length, and the diameter of the cylindrical object. The movement of a carbon fiber was measured with a CCD camera. The observed experimental results agree well with the theoretical results.Accepted versio