ORCID Profile
0000-0003-3779-6535
Current Organisations
Nanyang Technological University
,
Nanyang Technological University Temasek Laboratories
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Publisher: American Physical Society (APS)
Date: 07-09-2018
Publisher: American Physical Society (APS)
Date: 20-11-2018
Publisher: Springer International Publishing
Date: 12-2019
Publisher: IOP Publishing
Date: 19-04-2017
Publisher: American Chemical Society (ACS)
Date: 16-02-2017
DOI: 10.1021/ACS.ANALCHEM.6B05053
Abstract: We introduce an effective method to actively induce droplet generation using negative pressure. Droplets can be generated on demand using a series of periodic negative pressure pulses. Fluidic network models were developed using the analogy to electric networks to relate the pressure conditions for different flow regimes. Experimental results show that the droplet volume is correlated to the pressure ratio with a power law of 1.3. Using a pulsed negative pressure at the outlet, we are able to produce droplets in demand and with a volume proportional to the pulse width.
Publisher: IEEE
Date: 05-2016
Publisher: Springer Science and Business Media LLC
Date: 12-12-2018
Publisher: MDPI AG
Date: 25-11-2016
DOI: 10.3390/MI7120216
Publisher: American Chemical Society (ACS)
Date: 25-11-2020
DOI: 10.1021/ACS.ANALCHEM.9B04219
Abstract: We introduce a unique system to achieve on-demand droplet merging and splitting using a perpendicular AC electric field. The working mechanism involves a micropillar to split droplets, followed by electrocoalescence using an AC electric field. Adjusting the parameters of the AC signal and conductivity of the fluid result in different merging regimes. We observed a minimum threshold voltage and a strong influence of the surfactant. We hypothesize that the merging process is caused by dipole-dipole coalescence between the daughter droplets. At the same time, adjustment of the conductivity reveals a shift in the merging regimes and can be explained with an electric circuit diagram. Size-based sorting using this merging phenomenon is subsequently demonstrated, where alternate, single, double, and triple droplets sorting were achieved. The concept presented in this paper is potentially useful for drug dispensing or multivolume digital polymerase chain reaction, as droplets of multiple sizes can be generated simultaneously.
Publisher: Springer Science and Business Media LLC
Date: 20-03-2017
Publisher: Springer Science and Business Media LLC
Date: 03-2020
Publisher: American Chemical Society (ACS)
Date: 12-02-2019
DOI: 10.1021/ACS.LANGMUIR.8B03486
Abstract: Interfacial gas enrichment (IGE) of dissolved gases in water is shown to govern the strong attraction between solid hydrophobic surfaces of an atomic force microscopy (AFM) colloidal probe and solid substrate. However, the role of IGE in controlling the attraction between fluid-fluid interfaces of foam films and emulsion films is difficult to establish by AFM techniques because of the extremely fast coalescence. Here, we applied droplet-based microfluidics to capture the fast coalescence event under the creeping flow condition and quantify the effect of IGE on the drainage and stability of water films between coalescing oil droplets. The amount of dissolved gases is controlled by partially degassing the oil phase. When the amount of dissolved gases (oxygen) in oil decreases (from 7.89 to 4.59 mg/L), the average drainage time of coalescence significantly increases (from 19 to 50 ms). Our theoretical quantification of the coalescence by incorporating IGE into the multilayer van der Waals attraction theory confirms the acceleration of film drainage dynamics by the van der Waals attractive force generated by IGE. The thickness of the IGE layer decreases from 5.5 to 4.9 nm when the amount of dissolved gas decreases from 7.89 to 4.59 mg/L. All these results establish the universal role of dissolved gases in governing the strong attraction between particulate hydrophobic interfaces.
Publisher: American Chemical Society (ACS)
Date: 23-01-2019
DOI: 10.1021/ACS.ANALCHEM.8B05712
Abstract: Focusing and separation of particles such as cells at high throughput is extremely attractive for biomedical applications. Particle manipulation based on inertial effects requires a high flow speed and thus is well-suited to high-throughput applications. Recently, inertial focusing and separation using curvilinear microchannels has been attracting a great amount of interest because of the linear structure for parallelization, small device footprint, superior particle-focusing performance, and easy implementation of particle separation. However, the curvature directions of these microchannels alternate, leading to variations in both the magnitude and direction of the induced secondary flow. Accumulation of this variation along the channel causes unpredictable behaviors of particles. This paper systematically investigates the inertial-focusing phenomenon in low-aspect-ratio symmetric sinusoidal channels. First, we comprehensively studied the effects of parameters such as viscosity, flow conditions, particle size, and geometric dimensions of the microchannel on differential particle focusing. We found that particle inertial focusing is generally independent of fluid kinematic viscosity but highly dependent on particle size, flow conditions, and channel dimensions. Next, we derived an explicit scaling factor and included all four dimensionless parameters (particle-blockage ratio, curvature ratio, Dean number, and channel aspect ratio) in a single operational map to illustrate the particle-focusing patterns. Finally, we proposed a rational guideline to intuitively instruct the design of channel dimensions for separation of a given particle mixture.
Publisher: American Chemical Society (ACS)
Date: 04-03-2016
Publisher: AIP Publishing
Date: 06-2020
DOI: 10.1063/5.0004736
Abstract: We demonstrate a method to create surfactant-free core–shell microcapsules in a hydrophilic polydimethylsiloxane microfluidic device. An ultraviolet light curable polymer was used to encapsulate an oil core. These microcapsules ensure contamination-free compartmentation of the core material without any surfactant, while maintaining the monodispersed generation at a rate of 100 microcapsules per second. The device fabrication process is greatly simplified without the alignment of microchannels and hydrophobic/hydrophilic surface treatment. After drying, physically shaking the collection chamber can crack the capsule to release the liquid core material. Such solid microcapsules with a liquid core are ideal for the storage and delivery of oil-based materials in skincare products or reagents for biochemical assays.
Publisher: Elsevier BV
Date: 09-2019
Publisher: American Chemical Society (ACS)
Date: 05-05-2020
Location: Singapore
No related grants have been discovered for Adrian Teo.