Converting steady laminar flow to oscillatory flow through a hydroelasticity approach at microscales

Xia, Hou-Fu; Wang, Z. P.; Wang, Fan; Wijaya, A.; Wang, W.

doi:10.1039/c1lc20667b

Cited by 39 publications

(54 citation statements)

References 27 publications

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“…Figure 2 gives one example showing the oscillatory mixing in microchannels. The phenomenon is similar to our previous observation using an elastomer diaphragm (Xia et al 2012). At t = 0 ms, liquid 1 in the upper branch channel is pumped into the downstream channel.…”

Section: Mixing In Oscillatory Flowsupporting

confidence: 74%

“…According to our previous study, it will be reduced at higher P 0 (as demonstrated in Fig. 2 in Xia et al 2012). Therefore, at P 0 = 4.5 bar, the oscillation amplitude is larger than that at 6.0 bar.…”

Section: Effects Of Lipid Concentration and Anti-solvent To Solution mentioning

confidence: 62%

“…The system becomes unstable, and the diaphragm starts to vibrate up and down, converting the steady laminar flow to oscillatory flow. For more detailed discussion, please refer to Xia et al (2012Xia et al ( , 2014. The dimensions of current device are as follows: the diameter and depth of the main circular chamber: D mc = 4 mm, d mc = 150 µm.…”

Section: Mixer Device and Flow Controlmentioning

confidence: 99%

“…In this work, we will explore the relatively large-scale production of SLN using a microfluidic oscillator mixer developed in Xia et al (2012). The device contains an elastomer diaphragm which, above a critical pumping pressure, will vibrate spontaneously converting the otherwise laminar flow to oscillatory flow.…”

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confidence: 99%

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Anti-solvent precipitation of solid lipid nanoparticles using a microfluidic oscillator mixer

Xia

Seah

Liu

et al. 2014

Microfluid Nanofluid

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cosmetic and pharmaceutical applications. For dermatological applications, they provide many advantages such as enhanced chemical stability, increased skin hydration effect, and prolonged release (e.g., of perfumes, insect repellents). Cosmetic products containing lipid nanoparticles are already available in the market (Müller et al. 2007;Pardeike et al. 2009). SLN are also an attractive option when used as a drug carrier. It may overcome the problems such as insufficient concentration and poor drug solubility. Advantages also include low toxicity, increased drug stability, high drug load, and precise release control. (Mehnert and Mäder 2001;Almeida and Souto 2007;Belliveau et al. 2012).SLN can be produced through high-pressure homogenization. In this method, the lipid is pushed by high pressure through a narrow gap and accelerated to a high velocity. Large shear stress and cavitation forces will be produced that break the lipid into nanoparticles. This process is energy intensive as the required pressure is up to several hundred bars or even higher. SLN are also prepared by precipitation. The lipid is first dissolved in a solvent. Then, upon either evaporation of the solvent or addition of an anti-solvent, a nanoparticle dispersion will be formed by precipitation of the lipid (Sjöström and Bergenståhl 1992;Dong et al. 2012). Other methods include microemulsion, higher shear homogenization, and ultrasound. More detailed discussion can be found in Mehnert and Mäder (2001).The property of SLN is largely influenced by the size, uniformity, and morphology. Usually, smaller and more uniform SLN are preferred for higher stability, better absorption, and precise release control. In the precipitation synthesis method, one important factor that influences the quality of SLN is the mixing process. The mixing time need to be less than the precipitation time. Otherwise, slow and incomplete mixing will lead to large and wide Abstract The mixing process is critical in the anti-solvent precipitation process of micro-/nanoparticles. It may directly determine the quality of particles, especially the size and uniformity. In this study, a previously developed microfluidic oscillator mixer is used for anti-solvent precipitation of solid lipid (Gelucire 44/14) nanoparticles. This micromixer generates high-frequency oscillatory flow to enhance the fluid mixing. Based on the design, high flow rates of up to 50 ml/min can be achieved to allow relatively high throughput production. Results show that, within a wide concentration range from 10 to 300 mg/ml, solid lipid particles of 50-240 nm can be produced with the polydispersity index ranging from around 0.16 to 0.26. The influences of the anti-solvent to solution flow rate ratio, the geometrical and operating parameters of the oscillator mixer including the secondary chamber depth, and pumping pressure are investigated. For comparison, the same process was also conducted using a static chaotic mixer. Relevant findings provide useful reference for the performance and potential applicatio...

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Section: Mixing In Oscillatory Flowsupporting

confidence: 74%

Section: Effects Of Lipid Concentration and Anti-solvent To Solution mentioning

confidence: 62%

Section: Mixer Device and Flow Controlmentioning

confidence: 99%

mentioning

confidence: 99%

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Anti-solvent precipitation of solid lipid nanoparticles using a microfluidic oscillator mixer

Xia

Seah

Liu

et al. 2014

Microfluid Nanofluid

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“…1 Recently, analogy has been drawn between electronic transistors and microfluidic membrane-valves (lMV), which are used for self-regulated microfluidic circuits such as frequency-specific flow regulators, 2 digital logic circuits, [3][4][5][6] and oscillators. [7][8][9] Like an electronic circuit that operates itself with only a power source and thus minimize the use of its external controllers, the self-regulated microfluidic circuits have the potential to greatly reduce reliance on expensive and complex external controllers, which are barriers to broader use of microfluidic devices. A lMV is a crucial component that enables operation of self-regulated microfluidic devices through its on-off switching.…”

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Analyzing threshold pressure limitations in microfluidic transistors for self-regulated microfluidic circuits

Kim

Yokokawa

Takayama

2012

Applied Physics Letters

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This paper reveals a critical limitation in the electro-hydraulic analogy between a microfluidic membrane-valve (lMV) and an electronic transistor. Unlike typical transistors that have similar on and off threshold voltages, in hydraulic lMVs, the threshold pressures for opening and closing are significantly different and can change, even for the same lMVs depending on overall circuit design and operation conditions. We explain, in particular, how the negative values of the closing threshold pressures significantly constrain operation of even simple hydraulic lMV circuits such as autonomously switching two-valve microfluidic oscillators. These understandings have significant implications in designing self-regulated microfluidic devices. Electric circuit analogy is widely used in microfluidic circuit design and analysis. For example, electric resistors correspond to microfluidic channel resistances and capacitors to flexible membranes. The analogy is based on the similarity in equations between these circuit components. Since the theory and simulation methods of electric circuits are wellestablished, they greatly facilitate the design and analysis of various microfluidic circuits. 1 Recently, analogy has been drawn between electronic transistors and microfluidic membrane-valves (lMV), which are used for self-regulated microfluidic circuits such as frequency-specific flow regulators, 2 digital logic circuits, [3][4][5][6] and oscillators. [7][8][9] Like an electronic circuit that operates itself with only a power source and thus minimize the use of its external controllers, the self-regulated microfluidic circuits have the potential to greatly reduce reliance on expensive and complex external controllers, which are barriers to broader use of microfluidic devices. A lMV is a crucial component that enables operation of self-regulated microfluidic devices through its on-off switching.Similar to the electronic transistor, the lMV's on-off switching is determined by the relative difference between the source (P S ) minus gate pressure (P G ) versus the threshold pressure ( Figure 1). As depicted in Figure 1(a), when P S is sufficiently greater than P G , the membrane of the lMV deflects down and the lMV is on (open). In other words, the lMV is on when P S À P G is greater than opening threshold pressure (P th-open ). To turn off (close) the lMV, P S À P G is less than closing threshold pressure (P th-close ). In typical silicon transistors, 10,11 the difference between on and off threshold voltage is negligible, thus providing a large parameter space for the design and operation of large-scale integrated circuits. Pneumatic lMVs also exhibit small differences between opening (P th-open ) and closing (P th-close ) threshold pressures. 5,12 However, in self-regulated microfluidic devices, the detailed characteristic of lMV's threshold pressure in the context of other microfluidic parameters such as fluidic resistor and inflow rate is largely unknown.Here, we report that P th-open and P th-close are significantly differe...

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Autonomous Chemical Oscillator Circuit Based on Bidirectional Chemical‐Microfluidic Coupling

Paschew

Schreiter

Voigt

et al. 2016

Adv Materials Technologies

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A chemofluidic oscillator circuit that employs a hydrogel‐based chemofluidic transistor for chemical‐fluidic coupling is presented. It shows a period between 200 and 1000 s and alcohol concentrations oscillating between 2 wt% and 10 wt%. Because of the direct interaction with chemistry, chemofluidic transistors have the potential to facilitate labs‐on‐chips with enhanced functionality and scalability.

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Converting steady laminar flow to oscillatory flow through a hydroelasticity approach at microscales

Cited by 39 publications

References 27 publications

Anti-solvent precipitation of solid lipid nanoparticles using a microfluidic oscillator mixer

Anti-solvent precipitation of solid lipid nanoparticles using a microfluidic oscillator mixer

Analyzing threshold pressure limitations in microfluidic transistors for self-regulated microfluidic circuits

Autonomous Chemical Oscillator Circuit Based on Bidirectional Chemical‐Microfluidic Coupling

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