Hua Tan

Zebrafish (Danio rerio) emerged as a suitable vertebrate model organism in the 1960s, owing to its transparent embryos and ease of breeding. Research utilizing zebrafish as a model organism gained significant momentum in the 1970s, particularly in the field of developmental biology. Over the years, zebrafish has become an indispensable model across various domains of biological research. However, conventional techniques for handling zebrafish in research settings have been limited by challenges related to survival rates, throughput, and imaging capabilities. The advancements in microfluidics and Micro-Electro-Mechanical Systems (MEMS) technology have addressed many of these challenges, enabling significant progress in zebrafish-based studies. The integration of microchannels, which ensure laminar flow for precise liquid handling, alongside microsensors and actuators for trapping mechanisms and high-resolution imaging, has greatly enhanced experimental efficiency and precision. This review provides a comprehensive analysis of very recent advancements in Fish-on-Chip (FOC) technologies, with a focus on their applications in zebrafish research, including trapping, imaging, transportation, and studies involving drug screening and disease modeling. Furthermore, we discuss recent efforts in retaining progressively motile zebrafish sperm, which is increasingly critical to meeting the rising demand for diverse zebrafish lines. Finally, we discuss an automated microfluidic-based fish farm developed using these technologies and conclude the review by highlighting potential future directions for Fish-on-Chip (FOC) technology.

The split sleeve cold expansion process is broadly utilized in aerospace metallic structures to improve the fatigue life of fastener holes. However, the effectiveness of this process is highly affected by variations in key process parameters. This numerical parametric study investigates the effect of hole size variations up to 0.09 mm, frictional coefficient up to 0.1, and mandrel pulling angle up to 1.5° on the outcomes of the split sleeve cold expansion process for a 7.59‐mm hole in aluminum 2024‐T351. This study primarily focuses on two primary outcomes: residual stress fields and the evolution of pulling force. Explicit 3D FE models were developed using ABAQUS 6.19 to simulate the process. The results of this investigation indicate that geometric variations in hole diameter lead to a reduced magnitude of peak compressive residual stress and a smaller compression region at the hole’s entrance face by up to 24% when compared to the straight hole. When the mandrel’s pulling angle is 1.5°, the distribution of compressive residual stresses becomes asymmetrically around the hole, with a declining trend in circumferential compressive stress magnitude at the entry and exit faces near the hole. Additionally, an increase in the coefficient of friction from 0.05 to 0.1 results in an increase of the maximum pulling forces by 62%–74%; however, its impact on the circumferential residual stresses is minimal.

This study aims to improve the accuracy of the pulling force estimation by establishing the variable friction model of the dry-lubricated split sleeve when cold working an aluminum 2024-T3 hole. The variable friction model was empirically obtained from the friction experimental setup simplified from the split-sleeve cold expansion process. The contact-pressure-dependent variable friction model was derived through a systematic design of experiments approach with three different normal stress conditions, namely low normal stress (220 MPa), medium normal stress (440 MPa), and high normal stress (660 MPa), to cover the range of normal stresses occurred in the cold expansion process. A full quadratic response surface model was drawn for the friction coefficient's nonlinear relationship between the mandrel and the lubricated sleeve, depending on the normal stresses. The variable friction model was verified with 3-dimensional friction test finite element (FE) simulations. This FE modeling validates the variable friction model to predict the pulling forces with a sound agreement between the estimated and experimentally obtained values. We conducted split-sleeve cold expansion experiments to obtain the pulling force profile. Two three-dimensional (3D) FE numerical analyses of the same split-sleeve cold expansion process were conducted using the variable friction model and a constant frictional coefficient of 0.05. The pulling force profiles from the FE modeling with the variable friction model closely align with those from the experiments to show the four distinct regions.

In this study, we thoroughly investigate the impact dynamics of water droplets on a partially wetting substrate with a single hole. By conducting experiments using de-ionized water droplets and high-speed imaging, we observe various outcomes, including downward jetting without pinch-off, jetting with single and multiple pinch-offs, and the intriguing emergence of an upward jet during droplet recoil. A regime map is constructed to establish the relationship between the dynamics of the jet and the Weber number. We find the small amount of liquid leakage through the hole has a negligible effect on the maximum spreading of the droplet. We analyze the behavior of the downward jet resulting from droplet impact in terms of its length, speed, and breakup characteristics. The scaling relation between the maximum jet length before its breakup and the Weber number is derived and compared with experimental data. We find that the growth of the downward jet length follows a consistent power-law relationship with time regardless of impact velocity, while the maximum jet velocity scales linearly with the impact velocity, confirming the hydrodynamic focusing theory. The size of the head satellite droplet formed during the jet pinch-off process remains nearly constant across different Weber numbers. Additionally, we investigate the volume of ejected liquid through the microhole, observing an initial increase with the Weber number followed by a saturation point. The occurrence of the upward jet during droplet recoil is a significant finding, and we analyze its diameter, height, and velocity in relation to the Weber number.

Absorption of droplet by the powder media is a ubiquitous phenomenon in many natural and engineering processes, in which the diameter of droplets ranges from tens of micrometers (μm) to a few millimeters (mm) depending on the specific condition. In this study, we investigate the absorption process following the impact of the droplet with radii varying from mm- to μm-scale on nylon powder substrate. The fluid properties are varied by mixing the deionized water with isopropyl alcohol at different volume ratios. A syringe pipette tip is used to generate droplets of diameter ranging from 2.08 to 2.30 mm, whereas a drop-on-demand inkjet device is used to dispense droplets of diameter ranging from 88 to 140 μm. The absorption process of the single droplet is captured by a high-speed imaging system. We find that for mm- and μm-droplets there exists different critical surface tension below which the imbibition into the nylon powder can occur. With the proposed nondimensionalization process, the scattered data of dimensionless absorbed volume V and dimensionless time τ for different fluids generally collapse into a power law relation V~ τ^α, where the exponent α for mm-sized and μm-sized droplets is 0.856 and 0.518, respectively. The experimental data of μm droplets generally agree with the prediction of the Washburn equation for the unidirectional capillary flow, i.e. V~ τ ^0.5. However, the results of mm-droplets favor more the prediction of the 3D radial flow (i.e., a hemispherically advancing infiltration front inside the powder), V~ τ.

Residual Stress distribution and parametric influence of friction is studied for the split sleeve cold expanded holes in Al 2024 T351 alloy, by developing a three-dimensional finite element model of the process. Aluminium 2024 T351 alloy is very popular in aviation industry. Fastener holes in the alloy are necessary for the manufacturing process but creates potential area for

The jetting phenomenon associated with droplet impact upon a hydrophilic micropillared substrate was analyzed in detail using a high-speed camera. Viscosities of the fluids were varied using differing concentrations of glycerol in deionized water. This paper aims to connect similarities between this form of capillary jetting and another well-known jetting phenomenon from the bubble bursting. Both experience a cavity collapse when opposing fluid fronts collide which causes a singularity at the liquid surface, thus leading to the occurrence of jetting. Following processes used to define scaling laws for bubble bursting, a similar approach was taken to derive scaling laws for the dimensionless jet height, jet radius, base height, and radius of the jet base with respect to dimensionless time for the jetting phenomenon associated with the droplet impact. The development of a top droplet before the breakup of the jet also allows the examination of a scaling law for the necking diameter. We find that with the proper scaling factors, the evolution of the jet profile can collapse into a master profile for different fluids and impact velocities. The time dependence of the necking diameter before the jet breakup follows the power law with an exponent of ~2/3. Contrastingly, for other jet parameters such as the radius and height, the power law relationship with time dependence was not found to have a clear pattern that emerged from these studies.