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[Laser Institute of America ICALEO? 2015: 34th International Congress on Laser Materials Processing, Laser Microprocessing and Nanomanufacturing - Atlanta, Georgia, USA (October 18–22, 2015)] International Congress on Applications of Lasers & Electro-Optics - Rapid direct laser writing of microfluidic device on siloxane molds for microreplication
摘要： Microfluidic devices are usually made by replication with PDMS (polydimethylsiloxane) from masters produced using MEMS microfabrication technology. PDMS is the material of choice for pattern transfer due to its flexibility, chemical stability, and low surface energy. Creating functional microfluidic devices that integrate manipulation components (i.e., micro-filters or mixers) using MEMS technology is a costly and time consuming operation. This limits the ability to test design variants through agile, rapid prototyping of the device. Direct PDMS fabrication is an attractive alternative which require a direct writing technology. This work demonstrates direct structuring of PDMS with picoseconds pulsed laser, used for rapid creation of a mould for replication of the devices themselves. The main hindrance found in PDMS direct writing is the generation of decomposed layers which limits the further processing and compromises surface quality. The first results demonstrated that a microfluidic device with integrated functional microfeatures can be effectively fabricated without the formation of decomposed PDMS by carefully optimising the laser parameters and machining strategy. Complete 3x3mm microfluidic devices (with the integration of multistage filter components) were thus fabricated in under 2 minutes with lateral resolution down to 10μm. Hence, an optimized set of parameters allows fast rapid prototyping of microfluidic devices for development and proof of new concepts, using ultrafast lasers.
关键词： microfluidic devices,picoseconds pulsed laser,direct laser writing,rapid prototyping,PDMS
更新于2025-09-11 14:15:04
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Advanced Design of Microfluidic Chip Based on SPP-LSP Plasmonic Coupling for SERS Detection with High Sensitivity and Reliability
摘要： In this work, we propose the preparation and investigation of advanced microfluidic Surface-enhanced Raman spectroscopy (SERS) chip with the design, allowing high SERS enhancement and analysis reproducibility. Proposed chip implements the creation of periodical metal structure (grating) inside the microfluidic chip and further immobilization of gold multibranched nanoparticles (AuMs) with shaped edges on the grating surface. Such approach allows achieving plasmonic coupling between the surface plasmon polariton wave, excited on the Au grating, and localized surface plasmon, excited on sharped edges of AuMs. As a result, the high enhancement of electric field in the space between AuMs was achieved, which results in the high SERS enhancement factor, confirmed by both, theoretical calculation and experimental measurements with typical SERS analyte – R6G. In particular, vanishingly small concentration of R6G is possible to detect using the proposed plasmonic coupling, which sensitivity significantly exceeds previously reported limits in the case of microfluidic SERS measurements. We also observed the dependency of SERS intensity on the microfluidic flow rate and demonstrated the perfect reliability of the SERS signal, measured in the microfluidic regimes under the constant flow rate.
关键词： SERS,plasmonic coupling,gold multibranched nanoparticles,microfluidic chip,R6G,Surface-enhanced Raman spectroscopy
更新于2025-09-11 14:15:04
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Femtosecond laser fabrication of silver nanostructures on glass for surface enhanced Raman spectroscopy
摘要： We report on an optimized fabrication protocol for obtaining silver nanoparticles on fused silica substrates via laser photoreduction of a silver salt solution. We find that multiple scans of the laser over the surface leads to a more uniform coverage of densely packed silver nanoparticles of approximately 50 nm diameter on the fused silica surface. Our substrates yield Raman enhancement factors of the order of 1011 of the signal detected from crystal violet. We use a theoretical model based on scanning electron microscope (SEM) images of our substrates to explain our experimental results. We also demonstrate how our technique can be extended to embedding silver nanoparticles in buried microfluidic channels in glass. The in situ laser inscription of silver nanoparticles on a laser machined, sub-surface, microfluidic channel wall within bulk glass paves the way for developing 3D, monolithic, fused silica surface enhance Raman spectroscopy (SERS) microfluidic sensing devices.
关键词： SERS,surface enhanced Raman spectroscopy,microfluidic sensing devices,femtosecond laser fabrication,silver nanostructures
更新于2025-09-11 14:15:04
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Plasmonic Biosensors on a Chip for Point-of-Care Applications
摘要： Plasmonic biosensors, mainly those based on plasmonics technology, have emerged recently as a possible solution for disease diagnostics at the point-of-care (POC) level. There is an increasing demand for cost-effective, affordable, and robust POC platforms for the diagnosis of infectious and chronic diseases. These platforms should also need only low-sample consumption and be capable of providing a real-time response with a high sensitivity. A biosensor platform, employing small integrated devices, could perform rapid, label-free assays.
关键词： LSPR,microfluidic devices,Plasmonic biosensors,SPR,point-of-care
更新于2025-09-11 14:15:04
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[IEEE 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz2018) - Nagoya, Japan (2018.9.9-2018.9.14)] 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Terahertz Microfluidic Metamaterial Biosensor for Tiny Volume Liquid Samples
摘要： We present a novel multi-microfluidic-channel metamaterial biosensor (MCMB) for highly sensitive terahertz (THz) sensing of tiny volume liquid samples. The multi-channels are set mainly in the strong electric field enhancement area of the metamaterial, which significantly decreases the liquid amount and enhances interaction between the sensing targets and the THz wave (thus increasing the sensitivity). The water sensing results demonstrate the effectiveness of this proposed design and the great potential in THz biosensing.
关键词： metamaterial,biosensor,liquid samples,terahertz,microfluidic
更新于2025-09-10 09:29:36
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Paper-Based Origami Photoelectrochemical Sensing Platform with TiO <sub/>2</sub> /Bi <sub/>4</sub> NbO <sub/>8</sub> Cl/Co-Pi Cascade Structure Enabling of Bidirectional Modulation of Charge Carrier Separation
摘要： A bidirectional modulation of photoinduced charge carrier separation strategy based on TiO2/Bi4NbO8Cl/Co-Pi was proposed in microfluidic paper based photoelectrochemical analytical device (μ-POAD). Perovskite Bi4NbO8Cl with high charge carrier mobility was employed as visible light absorber, sandwiching between electron transporting material (ETM) and hole transporting material (HTM). Paper based TiO2 nanosheet arrays (PTNAs) serve as the ETM to provide a direct pathway for electron transport and Co-Pi works as the HTM to extract holes. Driven by a built-in electric field, the generated electrons of Bi4NbO8Cl are extracted by PTNAs, while holes are drawn toward Co-Pi, achieving efficient carrier separation. Remarkably, it is the first time that the HTM was introduced into μ-POAD to efficiently output holes and enhance the sensitivity. With the aid of ETM and HTM, 2.59 and 14.6 times higher photocurrent density was obtained compared with PTNAs/Bi4NbO8Cl and Bi4NbO8Cl photoelectrode, respectively. Benefiting from this dramatic photocurrent signal, ultrasensitive detection of β human chorionic gonadotrophin is realized with the linear range of 0.01?3000 IU L?1 and detection limitation of 0.005 IU L?1. This work demonstrates the importance of efficient carrier separation to the sensitivity of μ-POAD and paves the way for developing a high-performance analytical device.
关键词： bidirectional modulation,microfluidic paper based photoelectrochemical analytical device,photoinduced charge carrier separation,β human chorionic gonadotrophin,TiO2/Bi4NbO8Cl/Co-Pi
更新于2025-09-10 09:29:36
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Quantitative Determination of Urine Glucose: Combination of Laminar Flow in Microfluidic Chip with SERS Probe Technique
摘要： A surface-enhanced Raman scattering(SERS) sensing approach for urine glucose was developed based on the laminar flow technology in a cross-type microfluidic chip with SERS probes, 4-mercaptophenylboronic acid (MPBA) functionalized Ag nanoparticles. MPBA as the glucose receptor can identify and bind up with glucose at a molar ratio of 2:1, which can cause the aggregation of SERS probes at a certain position of the chip channel and further enhance the SERS signal of MPBA significantly. Thus, the quantitative SERS detection of glucose was achieved indirectly. No sample pretreatment and separation were needed in this method since the SERS detection was achieved in the gradient diffusion and molecular recognition processes between urine glucose and SERS probe in the laminar flow, which simplified the sample treatment procedures, saved detection time and made it feasible for clinic applications. This method shows a good linear relationship within human body’s normal physiological range and has high sensitivity and selectivity. The lowest detection concentration can reach 1.0 mg/dL.
关键词： Urine glucose,4-Mercaptophenylboronic acid,Microfluidic chip,Surface-enhanced Raman scattering(SERS)
更新于2025-09-10 09:29:36
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Numerical investigation of electrowetting-based droplet splitting in closed digital microfluidic system: Dynamics, mode, and satellite droplet
摘要： In this paper, the splitting of microdroplet in a closed electrowetting-based digital microfluidic system has been studied via a numerical model. The governing equations for the fluid flow are solved by a finite volume formulation with a two-step projection method on a fixed computational domain. The free surface of the liquid is tracked by a coupled level-set and volume-of-fluid method, with the surface tension at the free surface computed by continuum surface force scheme. Contact angle hysteresis is implemented as an essential component of electrowetting modeling, and a simplified viscous force model is adopted to evaluate the viscous stress based on the Hele-Shaw model. Excellent agreement has been achieved between the numerical and published experimental results. A parametric study has been performed in which the effects of viscous stress, channel height, static contact angles, contact angle hysteresis, and electrode size on the splitting process have been analyzed. Three distinct splitting modes, which are “splitting with satellite droplet,” “normal splitting,” and “splitting cessation,” have been discussed. Based on the competition between the curvature in the z-direction (κz) and that on the x-y plane (κxy), the physical mechanism that separates the splitting into these three modes has been revealed. More importantly, a dimensionless parameter ?κ has been proposed, which can be used for (a) determining the splitting mode and (b) estimating satellite droplet volume for electrowetting-induced droplet splitting process.
关键词： contact angle hysteresis,digital microfluidic system,droplet splitting,electrowetting,numerical model
更新于2025-09-10 09:29:36
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[IEEE 2018 IEEE 3rd International Conference on Image, Vision and Computing (ICIVC) - Chongqing (2018.6.27-2018.6.29)] 2018 IEEE 3rd International Conference on Image, Vision and Computing (ICIVC) - Low Resolution Cell Image Edge Segmentation Based on Convolutional Neural Network
摘要： An low-resolution cell images captured by a lens-free imaging system is presented in this paper. The resolution of this cell images is impacted by the low and experimental cell segmentation methods to solve the original cell images is not robust and sensitive to noise. So based on the convolutional neural network, an optimized CSnet method is proposed in this paper for automatically segmenting cell. In the proposed method, the produced data set will be sent into the convolutional neural network firstly for training to obtain an optimized convolution neural network segmentation model. And then, the pre-divided images acquired by the lens-free imaging system are loaded into the segmentation model to get the segmentation images. Finally, our proposed method in this paper is tested in a neural network framework built in keras. The experimental results show that the accuracy of our proposed method can reach about 96%. At the same time, it also can implement batch segmentation automatically and make the problem of heavy task for segmentation better.
关键词： convolutional neural network,cell segmentation,Lensfree imaging,microfluidic chip
更新于2025-09-10 09:29:36
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High-speed velocimetry in microfluidic protein mixers using confocal fluorescence decay microscopy
摘要： A method to measure fluid speeds on the order of 10,000 mm/s in microchannels is presented. A microfluidic protein mixer is manufactured with a 170 μm microscope coverslip bottom that interfaces with a confocal florescence microscope using a water-immersed Olympus UPLSAPO 60XW objective to create a diffraction-limited confocal volume. A diode laser with a repetition rate of 1 MHz is used to study Poiseuille flows at average speeds of 5000, 6000 and 7000 mm/s by exciting tris(2,2′-bipyridine)ruthenium(II) hexafluorophosphate solution at 1 μmol/L concentration flowing through the micro-mixer in the confocal volume. Decays collected using a time-correlated single photon counting card at each grid point are characterized by the first moment of the decay and curve fitted with the theoretical Poiseuille flow solutions. It was found that curve fitting with higher average speeds results in lower errors. A fluorescence correlation study was then carried out at different depths in the micro-mixer to understand the raw data profiles observed using the diode laser. A mixing study was then carried out using a Ti-Sapphire laser with a repetition rate of 3.8 MHz. A Poiseuille flow at 7000 mm/s was measured using the Ti-Sapphire laser and then curve fitted to the theoretical Poiseuille flow solution. The curve fit was then applied to the complicated flow region to determine speed. Results of the experimental mixing study are also compared to direct numerical simulation results.
关键词： Microfluidic protein mixers,High-speed velocimetry,Poiseuille flows,Fluorescence correlation spectroscopy,Confocal fluorescence decay microscopy
更新于2025-09-09 09:28:46