Study of a liquid plug-flow thermal cycling technique using a temperature gradient-based actuator

Advances in droplet digital polymerase chain reaction on microfluidic chips

The PCR technique has been known to the general public since the pandemic outbreak of COVID-19. This technique has progressed through three stages: from simple PCR to real-time fluorescence PCR to digital PCR. Among them, the microfluidic-based droplet digital PCR technique has attracted much attention and has been widely applied due to its advantages of high throughput, high sensitivity, low reagent consumption, low cross-contamination, and absolute quantification ability. In this review, we introduce various designs of microfluidic-based ddPCR developed within the last decade. The microfluidic-based droplet generation methods, thermal cycle strategies, and signal counting approaches are described, and the applications in the fields of single-cell analysis, disease diagnosis, and pathogen detection are introduced. Further, the challenges and prospects of microfluidic-based ddPCR are discussed. We hope that this review can contribute to the further development of the microfluidic-based ddPCR technique.

A sample-to-answer DNA detection microfluidic system integrating sample pretreatment and smartphone-readable gradient plasmonic photothermal continuous-flow PCR

We report a microfluidic system integrating sample pretreatment and smartphone-readable gradient plasmonic photothermal continuous-flow PCR, paving the way for low-cost and rapid implementation of PCR diagnostics.

Magnetohydrodynamic Moving Liquid Plug Within a Microchannel: Analytical Solutions

The wide applications of plug flows in microscale in science and engineering help them attract a great deal recent interest. An analytical study is undertaken here to study the impacts of a transversely applied external uniform magnetic field affecting the motion of liquid in the plug in terms of hydrodynamic mixing properties. The well-known symmetric vortex structure occurring in a long plug with moderate aspect ratio is observed to be preserved, while the recirculation phenomenon is highly affected by the action of the magnetic field. The decelerating feature of Lorentz force on the liquid motion is illuminated by reducing the strength of the recirculating vortex moving towards the upper and lower walls. The effects of magnetic field on the flow resistance of the liquid plug as well as on the plug circulation rate and on the axial flux are also clarified. The liquid plug considered here is shown to be fully consistent with the continuous liquid flow in a channel whose exact solution is further extracted.

Strategic Shuffling of Clay Layers to Imbue Them with Responsiveness

Layers of naturally occurring clay minerals are rearranged to prepare highly sensitive multiresponsive clay-clay bilayer membrane (CCBM). The CCBM introduced here responds to the minuscule changes in the surrounding environments including temperature, humidity, and presence of solvent vapors by morphing in specific manners. Strips cut from CCBM exhibit up to 588 N kg^-1 force output when exposed to temperature fluctuations. Inheriting the natural stability of clay minerals, CCBM demonstrates extreme robustness, heating up to 500 °C, cooling with liquid N₂ and exposure to corrosive chemical vapors did not deteriorate its bending performance. Mechanistic studies suggest that shape transformations of CCBM are driven by the unequal response of its components to external stimuli.

Light-Activated Rapid-Response Polyvinylidene-Fluoride-Based Flexible Films

The design strategy and mechanical response mechanism of light-activated, rapid-response, flexible films are presented. Practical applications as a microrobot and a smart spring are demonstrated.