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Optically-Controlled Closable Microvalves for Polymeric Centrifugal Microfluidic Devices
摘要： Microvalving is a pivotal component in many microfluidic lab-on-a-chip platforms and micro-total analysis systems (μTAS). Effective valving is essential for the integration of multiple unit operations, such as, liquid transport, mixing, aliquoting, metering, washing, and fractionation. The ideal microfluidic system integrates numerous, sequential unit operations, provides precise spaciotemporal reagent release and flow control, and is amenable to rapid, low-cost fabrication and prototyping. Centrifugal microfluidics is an attractive approach that minimizes the need for supporting peripheral hardware. However, many of the microfluidic valving methods described in the literature suffer from operational limitations and fail when high rotational frequencies or pressure heads are required early in the analytical process. Current approaches to valve closure add unnecessary complexity to the microfluidic architecture, require the incorporation of additional materials such as wax, and entail extra fabrication steps or processes. Herein we report the characterization and optimization of a laser-actuated, closable valve method for polymeric microfluidic devices that ameliorates these shortcomings. Under typical operational conditions (rcf ≤ 605 *g) a success rate >99% was observed, i.e. successful valve closures remained leak free through 605 *g. Implementation of the laser-actuated closable valving system is demonstrated on an automated, centrifugally driven dynamic solid phase extraction (dSPE) device. Compatibility of this laser-actuated valve closure approach with commercially available polymerase chain reaction (PCR) assays is established by the generation of full 18-plex STR profiles from DNA purified via on-disc dSPE. This novel approach promises to simplify microscale valving, improve functionality by increasing the number of integrated unit operations, and allow for the automation of progressively complex biochemical assays.
关键词： PCR,laser-actuated valve,microvalving,dynamic solid phase extraction,polymeric microfluidic devices,centrifugal microfluidics
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE Asia-Pacific Microwave Conference (APMC) - Singapore, Singapore (2019.12.10-2019.12.13)] 2019 IEEE Asia-Pacific Microwave Conference (APMC) - A terahertz microfluidic sensor based on metasurface
摘要： We present a microfluidic sensor integrated with metasurface and a terahertz measuring system used for it. To obtain better sensing sensitivity, numerical simulations were conducted to determine the structure and excitation mode for metasurface. A method to obtain the concentration of sample solution was given as an application of the sensor. Asymmetry metasurface are discussed with figure of merit. A new tradeoff index FD is defined to assess the performance of microfluidic sensor and the best metasurface for our microfluidic sensor is selected through FD.
关键词： Fano resonance,microfluidic sensor,metasurface
更新于2025-09-19 17:13:59
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High-Efficiency Small Sample Microparticle Fractionation on a Femtosecond Laser-Machined Microfluidic Disc
摘要： The fabrication and testing of microfluidic spinning compact discs with embedded trapezoidal microchambers for the purpose of inertial microparticle focusing is reported in this article. Microparticle focusing channels require small features that cannot be easily fabricated in acrylic sheets and are complicated to realize in glass by traditional lithography techniques; therefore, the fabrication of microfluidic discs with femtosecond laser ablation is reported for the first time in this paper. It could be demonstrated that high‐efficiency inertial focusing of 5 and 10 μm particles is achieved in a channel with trapezoidal microchambers regardless of the direction of disc rotation, which correlates to the dominance of inertial forces over Coriolis forces. To achieve the highest throughput possible, the suspension concentration was increased from 0.001% (w/v) to 0.005% (w/v). The focusing efficiency was 98.7% for the 10 μm particles and 93.75% for the 5 μm particles.
关键词： femtosecond laser,microfluidics,microparticle separation,microfluidic disc
更新于2025-09-19 17:13:59
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Toroidal metasurfaces integrated with microfluidic for terahertz refractive index sensing
摘要： A terahertz refractive index sensor consisting of toroidal dipole resonance metasurface integrated with microfluidic channel is proposed. The excitation of toroidal dipole resonance in this metasurface and the localized electromagnetic field enhancement in microfluidic channel are investigated comprehensively. Numerical results show that the calculated quality factor and the corresponding figure of merit can reach 1103 and 244, much higher than previously reported terahertz metamaterials sensors. Moreover, the refractive index sensing capabilities of non-polar and polar liquids are also investigated, which demonstrate the resonant frequency shift does not depend on the losses of analytes and show this device can be used for sensing various materials, including highly absorptive materials. This proposed structure can be extended to work in other frequency regions and has potential applications in high performance gases, liquids and biological materials sensing.
关键词： toroidal dipole,metasurfaces,microfluidic,refractive index sensing,terahertz
更新于2025-09-19 17:13:59
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Optofluidic laser speckle image decorrelation analysis for the assessment of red blood cell storage
摘要： Red blood cells (RBCs) undergo irreversible biochemical and morphological changes during storage, contributing to the hemorheological changes of stored RBCs, which causes deterioration of microvascular perfusion in vivo. In this study, a home-built optofluidic system for laser speckle imaging of flowing stored RBCs through a transparent microfluidic channel was employed. The speckle decorrelation time (SDT) provides a quantitative measure of RBC changes, including aggregation in the microchannel. The SDT and relative light transmission intensity of the stored RBCs were monitored for 42 days. In addition, correlations between the decorrelation time, RBC flow speed through the channel, and relative light transmission intensity were obtained. The SDT of stored RBCs increased as the storage duration increased. The SDTs of the RBCs stored for 21 days did not significantly change. However, for the RBCs stored for over 35 days, the SDT increased significantly from 1.26 ± 0.27 ms to 6.12 ± 1.98 ms. In addition, we measured the relative light transmission intensity and RBC flow speed. As the RBC storage time increased, the relative light transmission intensity increased, whereas the RBC flow speed decreased in the microchannel. The optofluidic laser speckle image decorrelation time provides a quantitative measure of assessing the RBC condition during storage. Laser speckle image decorrelation analysis may serve as a convenient assay to monitor the property changes of stored RBCs.
关键词： laser speckle,image decorrelation,microfluidic channel,Optofluidic,RBC aggregation,speckle decorrelation time,red blood cell storage
更新于2025-09-19 17:13:59
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Novel Nanoplasmonic Structure based Integrated Microfluidic Biosensors for Label-Free in Situ Immune Functional Analysis
摘要： The study of immune functional responses is essential to understanding the central role of the immune system in providing immunological host defense and its intercommunication with other systems. The recent development of integrated microfluidic cytokine biosensors has established a new paradigm to identify, isolate, and study immune cell subtypes, cell functions, and intercellular communications that constitute those responses. In this minireview, we highlight the most recent progress in label-free cytokine detection based on localized surface plasmon resonance optical sensing. We present the applications of newly identified plasmonic nanostructures and the integration with advanced microfluidic devices for novel lab-on-a-chip biosensing systems and discuss the associated challenges and future perspective of such integrative sensing technologies for next-generation immune functional analysis.
关键词： immune functional responses,localized surface plasmon resonance,microfluidic cytokine biosensors,plasmonic nanostructures,lab-on-a-chip biosensing systems
更新于2025-09-19 17:13:59
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Sensitivity Enhancement of a Concave Shaped Optical Fiber Refractive Index Sensor Covered with Multiple Au Nanowires
摘要： In the present paper, a new kind of concave shaped refractive index sensor (CSRIS) exploiting localized surface plasmon resonance (LSPR) is proposed and numerically optimized. The LSPR effect between polaritons and the core guided mode of designed CSRIS is used to enhance the sensing performance. The sensor is characterized for two types of sensing structures coated with gold (Au) film and Au nanowires (AuNWs), respectively. The influence of structural parameters such as the distance (D) of the concave shaped channel (CSC) from the core, the diameter of the nanowire (dn) and the size (s) of the CSC are investigated here. In comparison to Au film, the AuNWs are shown to significantly enhance the sensitivity and the performance of the designed sensor. An enhanced sensitivity of 4471 nm/RIU (refractive index unit) is obtained with AuNWs, for a wide range of analytes refractive index (na) varying between 1.33 to 1.38. However, for conventional Au film; the sensitivity of 808.57 nm/RIU is obtained for the same range of analytes.
关键词： nanowires,microfluidic channel,surface plasmon resonance,sensitivity,refractive index
更新于2025-09-16 10:30:52
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Cost-effective microfabrication of sub-micron-depth channels by femto-laser anti-stiction texturing
摘要： Micro Electro Mechanical Systems (MEMS) and microfluidic devices have found numerous applications in the industrial sector. However, they require a fast, cost-effective and reliable manufacturing process in order to compete with the conventional methods. Particularly, at the sub-micron scale, the manufacturing od devices are limited by the dimensional complexity. A proper bonding and stiction prevention of these sub-micron channels are two of the main challenges faced during the fabrication process of low aspect ratio channels. Especially, in case of using flexible materials such as polydimethylsiloxane (PDMS). This study presents a direct laser microfabrication method of sub-micron channels using an infrared (IR) ultrashort pulse (femtoseconds) capable of manufacturing extremely low aspect ratio channels. These microchannels are manufactured and tested varying their depth from 0.5 μm to 2 μm and width of 15, 20, 25, and 30 μm. The roughness of each pattern was measured by an interferometric microscope. Additionally, the static contact angle of each depth was studied to evaluate the influence of femtosecond laser fabrication method on the wettability of the glass substrate. PDMS, which is a biocompatible polymer, was used to provide a watertight property to the sub-micron channels and also to assist the assembly of external microfluidic hose connections. A 750nm depth watertight channel was built using this methodology and successfully used as a blood plasma separator (BPS). The device was able to achieve 100% pure plasma without stiction of the PDMS layer to the sub-micron channel within an adequate time. This method provides a novel manufacturing approach useful for various applications such as point-of-care devices.
关键词： Femtolaser,Biofabrication,Microfluidic,Blood/plasma separation
更新于2025-09-16 10:30:52
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Laser-induced heating for in situ DNA replication and detection in microchannels
摘要： This study proposes a method for in situ local deoxyribonucleic acid (DNA) replication and detection in a long DNA strand through laser-induced heating and strong avidin–biotin binding. To achieve the target DNA replication, dielectrophoresis was generated to stretch and immobilise DNA strands on both ends of the electrode. Subsequently, local DNA sequences were replicated using thermal cycles generated by laser-induced heating. Replicated double-stranded DNA products were captured in situ on a solid surface and detected using the fluorescence intensity of quantum dots (Qdots). The results revealed that after six laser-induced thermal cycles, the replicated local DNA sequence could be detected by analysing the difference between Qdot fluorescent intensity before and after replication. The proposed method is expected to improve the efficiency of biosample gene sequence analysis.
关键词： DNA replication,dielectrophoresis,microfluidic platform,laser-induced heating,quantum dots
更新于2025-09-16 10:30:52
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Microfluidic Channels Fabrication Based on Underwater Superpolymphobic Microgrooves Produced by Femtosecond Laser Direct Writing
摘要： A strategy is proposed here to fabricate microfluidic channels based on underwater superpolymphobic microgrooves with nanoscale rough surface structure on glass surface produced by femtosecond (fs) laser processing. The fs laser-induced micro/nanostructure on glass surface is able to repel liquid polydimethylsiloxane (PDMS) underwater, with the contact angle (CA) of 155.5 ± 2.5° and CA hysteresis of 2.7 ± 1.5° to a liquid PDMS droplet. Such phenomenon is defined as the underwater “superpolymphobicity”. Microchannels as well as microfluidic systems are easily prepared and formed between the underwater superpolymphobic microgrooves-textured glass substrate and the cured PDMS layer. Because the tracks of the laser scanning lines are programmable, arbitrary-shaped microchannels and complex microfluidic systems can be potentially designed and prepared through fs laser direct writing technology. The concept of “underwater superpolymphobicity” presented here offers us a new strategy for selectively avoiding the adhesion at the polymer/substrate interface and controlling the shape of cured polymers, none of these applications can find analogs in previously reported superwetting materials.
关键词： femtosecond laser,microfluidic channels,underwater superpolymphobicity,microfluidic systems,PDMS
更新于2025-09-12 10:27:22