Investigation of microscale particles using a microfluidic flow cytometer equipped with a sensitive photodetector

We have developed a sensitive optofluidic cytometer to investigate microscale particles. The flow cytometer is comprised of a microchannel that has a set of chevron-shaped grooves. Conducted by the chevrons, two sheath streams focus the core stream in the center of the microchannel three-dimensionally. The optofluidic cytometer is equipped with the new generation of photodetectors, multi-pixel photon counter (MPPC). MPPCs are highly sensitive photodetectors with extremely small footprint that deliver high gain values of up to 107. We have employed a MPPC as the photodetector unit in our cytometer. Two different sizes of high intensity fluorescent microspheres are run through the cytometer. The signal outputs from both particles are collected using a data acquisition unit for further statistical analysis. The emission light produced by samples is received by a multimode fiber that is located in 135-degree with respect to the excitation fiber. The effect of particle size on the range of collected signal output is investigated by observing the forward scattering emission from samples. Statistical analysis of collected signal proved that for 10.2 µm particles, the peak height, width, and consequently area are larger than 3.2 µm particles. Finally using a 35 mW diode laser three types of algae are characterized in the flow cytometer based on their sizes. COMSOL software was employed to simulate the concentration distribution along the microchannel

Characterization of Microscale Particles Using a Microfluidic Flow Cytometer Equipped With a Multi-Plex Photon Counter

ABSTRACT We have shown the design and fabrication of a microfluidic flow cytometer. The microfluidic flow cytometer has been used to characterize microspheres of different sizes. The device is consisted of a microchannel, electronics, and integrated optics. The microchannel has three inlets. Two inlets are used to introduce sheath flows and one middle inlet is assigned as sample inlet. The sample flow is hydrodynamically focused at the center of the microchannel by two side streams (sheath flows). Also arrays of four chevron grooves compress the sample flow from the top and bottom of the microchannel. The core flow contains microspheres at a certain concentration. Detection of the microspheres at the interrogation region of the channel is performed by integrated optics and electronics. The scattered light emitted from the microspheres is collected by a multi-plex photo diode (MPPC). The results are recorded using data acquisition (DAQ) unit. The MPPCs employed in the setup is the new generation of photon counter devices with an excellent detection limit, a compact size, and capability of recording data at high gain compared to previous generation of photodetectors such as photomultipliers or avalanche photon diodes. The flow cytometer was sensitive enough to collect data from 3 µm microspheres using such mentioned sensitive photon counting unit. We have also used COMSOL Multiphysics software to investigate velocity and pressure distribution as well as concentration distribution along the microchannel. The average voltage collected by MPPC was 1.9 V for 10.2 µm and 1.6 V for 3.2 µm microsphere

Investigation of microscale particles using a microfluidic flow cytometer equipped with a sensitive photodetector

We have developed a sensitive optofluidic cytometer to investigate microscale particles. The flow cytometer is comprised of a microchannel that has a set of chevron-shaped grooves. Conducted by the chevrons, two sheath streams focus the core stream in the center of the microchannel three-dimensionally. The optofluidic cytometer is equipped with the new generation of photodetectors, multi-pixel photon counter (MPPC). MPPCs are highly sensitive photodetectors with extremely small footprint that deliver high gain values of up to 107. We have employed a MPPC as the photodetector unit in our cytometer. Two different sizes of high intensity fluorescent microspheres are run through the cytometer. The signal outputs from both particles are collected using a data acquisition unit for further statistical analysis. The emission light produced by samples is received by a multimode fiber that is located in 135-degree with respect to the excitation fiber. The effect of particle size on the range of collected signal output is investigated by observing the forward scattering emission from samples. Statistical analysis of collected signal proved that for 10.2 µm particles, the peak height, width, and consequently area are larger than 3.2 µm particles. Finally using a 35 mW diode laser three types of algae are characterized in the flow cytometer based on their sizes. COMSOL software was employed to simulate the concentration distribution along the microchannel.</p

Flow boiling of r245fa in microgaps with staggered circular and hydrofoil pin fins

Dielectric fluids, including refrigerants, are electrically inert and are a good candidate as working fluid in two-phase microsystem cooling applications. In this study, R245fa is investigated for flow boiling in microgaps with height of 200 μm, spacing in the ranges of 200-225 μm (dense device) and 400-450 μm (sparse device) are studied. For heat fluxes up to 498 W/cm2, mass flux values ranging from 193 kg/m2s to 7896 kg/m2s and inlet temperatures ranging from 10 oC to 18 oC, average two-phase heat transfer coefficient up to 60 kW/m2K the devices are tested. High speed flow visualizations at frame rate of 2229 fps elucidate the flow boiling patterns inside the microgaps. The visualizations have shown different two-phase flow regimes such as bubbly, foggy, and slug flows that are generated in the pin finned area. The surface temperature values are calculated based on the obtained heaters temperature data and are plotted against the dissipated power for a wide range of heat flux for each experiment. An uncertainty analysis is also performed for the reported data. Single-phase and two-phase heat transfer coefficients and a comprehensive flow regime mapping is represented as part of this documentation. Also, pressure drop and heat transfer coefficients characterizations are done by developing correlations for single-phase and two-phase pressure drops, single-phase and two-phase heat transfer coefficients that perfectly match on all experimental data from devices.Ph.D

Multi-Pixel Photon Counters for Optofluidic Characterization of Particles and Microalgae

We have developed an optofluidic biosensor to study microscale particles and different species of microalgae. The system is comprised of a microchannel with a set of chevron-shaped grooves. The chevrons allows for hydrodynamic focusing of the core stream in the center using a sheath fluid. The device is equipped with a new generation of highly sensitive photodetectors, multi-pixel photon counter (MPPC), with high gain values and an extremely small footprint. Two different sizes of high intensity fluorescent microspheres and three different species of algae (Chlamydomonas reinhardtii strain 21 gr, Chlamydomonas suppressor, and Chlorella sorokiniana) were studied. The forward scattering emissions generated by samples passing through the interrogation region were carried through a multimode fiber, located in 135 degree with respect to the excitation fiber, and detected by a MPPC. The signal outputs obtained from each sample were collected using a data acquisition system and utilized for further statistical analysis. Larger particles or cells demonstrated larger peak height and width, and consequently larger peak area. The average signal output (integral of the peak) for Chlamydomonas reinhardtii strain 21 gr, Chlamydomonas suppressor, and Chlorella sorokiniana falls between the values found for the 3.2 and 10.2 μm beads. Different types of algae were also successfully characterized

Characterization of Microscale Particles Using a Microfluidic Flow Cytometer Equipped With a Multi-Plex Photon Counter

We have shown the design and fabrication of a microfluidic flow cytometer. The microfluidic flow cytometer has been used to characterize microspheres of different sizes. The device is consisted of a microchannel, electronics, and integrated optics. The microchannel has three inlets. Two inlets are used to introduce sheath flows and one middle inlet is assigned as sample inlet. The sample flow is hydrodynamically focused at the center of the microchannel by two side streams (sheath flows). Also arrays of four chevron grooves compress the sample flow from the top and bottom of the microchannel. The core flow contains microspheres at a certain concentration. Detection of the microspheres at the interrogation region of the channel is performed by integrated optics and electronics. The scattered light emitted from the microspheres is collected by a multi-plex photo diode (MPPC). The results are recorded using data acquisition (DAQ) unit. The MPPCs employed in the setup is the new generation of photon counter devices with an excellent detection limit, a compact size, and capability of recording data at high gain compared to previous generation of photodetectors such as photomultipliers or avalanche photon diodes. The flow cytometer was sensitive enough to collect data from 3 μm microspheres using such mentioned sensitive photon counting unit. We have also used COMSOL Multiphysics software to investigate velocity and pressure distribution as well as concentration distribution along the microchannel. The average voltage collected by MPPC was 1.9 V for 10.2 μm and 1.6 V for 3.2 μm microsphere.This is a conference proceeding from Proceedings of the ASME 2013 Summer Bioengineering Conference 1A (2013): 1, doi:10.1115/SBC2013-14800. Posted with permission.</p

Multi-Pixel Photon Counters for Optofluidic Characterization of Particles and Microalgae

We have developed an optofluidic biosensor to study microscale particles and different species of microalgae. The system is comprised of a microchannel with a set of chevron-shaped grooves. The chevrons allows for hydrodynamic focusing of the core stream in the center using a sheath fluid. The device is equipped with a new generation of highly sensitive photodetectors, multi-pixel photon counter (MPPC), with high gain values and an extremely small footprint. Two different sizes of high intensity fluorescent microspheres and three different species of algae (Chlamydomonas reinhardtii strain 21 gr, Chlamydomonas suppressor, and Chlorella sorokiniana) were studied. The forward scattering emissions generated by samples passing through the interrogation region were carried through a multimode fiber, located in 135 degree with respect to the excitation fiber, and detected by a MPPC. The signal outputs obtained from each sample were collected using a data acquisition system and utilized for further statistical analysis. Larger particles or cells demonstrated larger peak height and width, and consequently larger peak area. The average signal output (integral of the peak) for Chlamydomonas reinhardtii strain 21 gr, Chlamydomonas suppressor, and Chlorella sorokiniana falls between the values found for the 3.2 and 10.2 μm beads. Different types of algae were also successfully characterized.This article is from Biosensors 5 (2015): 308, doi:10.3390/bios5020308. Posted with permission.</p

Microfabrication of Highly Biocompatible Materials for Energy Applications

The objective of this paper is to use a microfluidic platform for fabricating biocompatible materials. One of the applications of this material is to be used as anode in a microbial fuel cell. In this process, the fibers are fabricated by utilizing a microchannel with three inlets, two sheath flows as well as a core flow. The core flow which is composed of gelatin is hydrodynamically focused by ethanol as the sheath flow. The microfibers created by this technique have various cross sections and will be used a structured porous scaffold. The porosity and biocompatibility of the structure make it an ideal choice for being used as a scaffold for bacterial attachment and biofilm formation. This will consequently results in developing a microbial fuel cell with a higher power density.This is a conference proceeding from Proceedings of the ASME 2013 7th International Conference on Energy Sustainability & 11th Fuel Cell Science, Engineering and Technology Conference (2013), 1. Posted with permission.</p