Demonstration of syringe-pump-induced disturbance in microfluidic system with low interfacial tension

Talk #21Junior Scientist, Postdoc and Student WorkshopsSyringe pump provides precise and constant flow rates so it is widely used in microfluidic research and applications. Most syringe pumps are mechanically driven and introduce fluctuations or pulses to the inlet flow and thus affect the steadiness of the flow. However, to the best of our knowledge, no evidences confirmed that these are really induced by syringe pumps. Here we introduce a robust visual detection of the unsteadiness induced by the stepping motor in a syringe pump, in form of ripples on the interface of an aqueous two-phase system which has low interfacial tension. We use a typical glass capillary device to generate a co-flow of two immiscible phases in our experiments [1]. The ripples are found to exhibit the same frequency as that delivered by the stepping motor of the syringe pump which drives the inner fluid, named as fpump, for various flow rates Q, syringe diameters D and advancing step sizes s, according to fpump = 4Q/(πD2s). The experimental results suggest that the low interfacial tension system can reflect the disturbance aroused from the inner pump, thus give an insight into understanding the fluctuation that syringe pumps induces and provide a way to test whether the unsteadiness in microfluidic system is related to syringe pump or not.published_or_final_versio

The dripping-to-jetting transition in a co-axial flow of aqueous two-phase systems with low interfacial tension

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The transformation dynamics towards equilibrium in non-equilibrium w/w/o double emulsions

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Perturbation-induced droplets for manipulating droplet structure and configuration in microfluidics

In this work, we mechanically perturb a liquid-in-liquid jet to manipulate the size and structure of the droplets formed from break-up of the jet. The induced break-up is relatively insensitive to fluctuations in the surrounding fluid flow. When the amplitude of perturbations is large and the interfacial tension of the liquid–liquid system is low, the size of the droplets can be precisely tuned by controlling the rate at which the liquid exits the tip of the dispensing nozzle through the frequency of perturbation. When applied to microfluidic devices with the appropriate geometry, our perturbation-induced droplet approach offers a strategy to manipulating droplet structures. We demonstrate that by varying the imposed perturbation frequency and phase lag, the structure of the multi-compartmental drops and the configuration of the resultant drops in the same flow condition can be manipulated. Moreover, after careful treatment of the wettability of the devices, we show that the structure of the droplets can be precisely controlled to change from single emulsion to double emulsion within the same device. The perturbation-induced droplet generation represents a new paradigm in the engineering of droplets, enhancing current droplet-based technologies for applications ranging from particle fabrication to confined micro-reactions.postprin

Musical Interfaces: Visualization and Reconstruction of Music with a Microfluidic Two-Phase Flow

Detection of sound wave in fluids can hardly be realized because of the lack of approaches to visualize the very minute sound-induced fluid motion. In this paper, we demonstrate the first direct visualization of music in the form of ripples at a microfluidic aqueous-aqueous interface with an ultra-low interfacial tension. The interfaces respond to sound of different frequency and amplitude robustly with sufficiently precise time resolution for the recording of musical notes and even subsequent reconstruction with high fidelity. Our work shows the possibility of sensing and transmitting vibrations as tiny as those induced by sound. This robust control of the interfacial dynamics enables a platform for investigating the mechanical properties of microstructures and for studying frequency-dependent phenomena, for example, in biological systems.published_or_final_versio

Episodic memory and sleep are involved in the maintenance of context-specific lexical information

Familiar words come with a wealth of associated knowledge about their variety of usage, accumulated over a lifetime. How do we track and adjust this knowledge as new instances of a word are encountered? A recent study (Cognition) found that, for homonyms (e.g., bank), sleep-associated consolidation facilitates the updating of meaning dominance. Here, we tested the generality of this finding by exposing participants to (Experiment 1; N = 125) nonhomonyms (e.g., bathtub) in sentences that biased their meanings toward a specific interpretation (e.g., bathtub-slip vs. bathtub-relax), and (Experiment 2; N = 128) word-class ambiguous words (e.g., loan) in sentences where the words were used in their dispreferred word class (e.g., "He will loan me money"). Both experiments showed that such sentential experience influenced later interpretation and usage of the words more after a night's sleep than a day awake. We interpret these results as evidence for a general role of episodic memory in language comprehension such that new episodic memories are formed every time a sentence is comprehended, and these memories contribute to lexical processing next time the word is encountered, as well as potentially to the fine-tuning of long-term lexical knowledge. (PsycInfo Database Record (c) 2023 APA, all rights reserved)

Efficient Implementation and Design of A New Single-Channel Electrooculography-based Human-Machine Interface System

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Direct observation of spin-polarised bulk bands in an inversion-symmetric semiconductor

Methods to generate spin-polarised electronic states in non-magnetic solids are strongly desired to enable all-electrical manipulation of electron spins for new quantum devices. This is generally accepted to require breaking global structural inversion symmetry. In contrast, here we present direct evidence from spin- and angle-resolved photoemission spectroscopy for a strong spin polarisation of bulk states in the centrosymmetric transition-metal dichalcogenide WSe$_2$. We show how this arises due to a lack of inversion symmetry in constituent structural units of the bulk crystal where the electronic states are localised, leading to enormous spin splittings up to $\sim\!0.5$ eV, with a spin texture that is strongly modulated in both real and momentum space. As well as providing the first experimental evidence for a recently-predicted `hidden' spin polarisation in inversion-symmetric materials, our study sheds new light on a putative spin-valley coupling in transition-metal dichalcogenides, of key importance for using these compounds in proposed valleytronic devices.Comment: 6 pages, 4 figure