Characterization Of Microfluidic Device Research Articles

Optofluidic bioimaging platform for quantitative phase imaging of lab on a chip devices using digital holographic microscopy

We propose a versatile 3D phase-imaging microscope platform for real-time imaging of optomicrofluidic devices based on the principle of digital holographic microscopy (DHM). Lab-on-chip microfluidic devices fabricated on transparent polydimethylsiloxane (PDMS) and glass substrates have attained wide popularity in biological sensing applications. However, monitoring, visualization, and characterization of microfluidic devices, microfluidic flows, and the biochemical kinetics happening in these devices is difficult due to the lack of proper techniques for real-time imaging and analysis. The traditional bright-field microscopic techniques fail in imaging applications, as the microfluidic channels and the fluids carrying biological samples are transparent and not visible in bright light. Phase-based microscopy techniques that can image the phase of the microfluidic channel and changes in refractive indices due to the fluids and biological samples present in the channel are ideal for imaging the fluid flow dynamics in a microfluidic channel at high resolutions. This paper demonstrates three-dimensional imaging of a microfluidic device with nanometric depth precisions and high SNR. We demonstrate imaging of microelectrodes of nanometric thickness patterned on glass substrate and the microfluidic channel. Three-dimensional imaging of a transparent PDMS optomicrofluidic channel, fluid flow, and live yeast cell flow in this channel has been demonstrated using DHM. We also quantify the average velocity of fluid flow through the channel. In comparison to any conventional bright-field microscope, the 3D depth information in the images illustrated in this work carry much information about the biological system under observation. The results demonstrated in this paper prove the high potential of DHM in imaging optofluidic devices; detection of pathogens, cells, and bioanalytes on lab-on-chip devices; and in studying microfluidic dynamics in real time based on phase changes.

Microfluidic circuits and systems

The possibilities envisioned by the characterization of microfluidic systems cover a wide range of both scientific demands and industrial requirements, from life sciences to fine chemistry, from food quality to other microbiology applications. In these fields, the development of analytical methods and technological solutions oriented to the creation of a firm and structured link between models and experimentation on microfluidic systems, opens up the way for the study and characterization of microfluidic devices and phenomena from a point of view related to system and control theory.

Apolydimethylsiloxane (PDMS) deformable diffraction grating formonitoring of local pressure in microfluidic devices

In this paper, a novel optical method for monitoringof local pressure in microfluidic devices using a deformablediffraction grating is presented. A test device was fabricatedwith transparent silicone elastomer - polydimethylsiloxane(PDMS) - using the replica moulding technique. The moulded PDMSchip and a flat glass plate have a bonding interface, whichdefines a 2 mm×2 mm diffraction grating and a200 µm wide, 20 µm deep microchannel. The gratingconsists of 5 µm wide, 2 µm deep rectangular groovesarrayed with a period of 10 µm. All the grooves areconnected to the microchannel, and deformed by internalpressure. The optical response of the device to pressureranging from -80 to 100 kPa is presented and compared with thetheoretical prediction. It is also demonstrated that the testdevice can be used for measurement of air flow rates rangingfrom 0 to 0.3 ml min-1. The major advantages of thismethod are simple design and inexpensive fabrication. Thismethod is not only desirable for flow characterization ofmicrofluidic devices, but also opens up the possibility ofproducing new types of fibre-optic pressure sensor andpressure-driven optical modulator.

Development and Characterization of Microfluidic Devices and Systems for Magnetic Bead-Based Biochemical Detection

This paper presents the development and characterization of a generic microfluidic system for magnetic bead-based biochemical detection. Microfluidic and electrochemical detection devices such as microvalves, flow sensors, biofilters, and immunosensors have been successfully developed and individually characterized in this work. Magnetically driven microvalves, pulsed-mode microflow sensors, magnetic particle separators as biofilters, and electrochemical immunosensors have been sep-arately fabricated and tested. The fabricated microfluidic components have been surface-mounted on the microfluidic motherboard for fully integrated microfluidic biochemical detection system. A magnetic bio-bead approach has been adopted for both sampling and manipulating target biological molecules. Magnetic beads were used as both substrate of antibodies and carriers of target antigens for magnetic bead-based immunoassay, which was chosen as a proof-of-concept for the generic microfluidic bio-chemical detection system. The microfluidic and electrochemical immunosensing experiment results obtained from this work have shown that the biochemical sensing capability of the complete microfluidic subsystem is suitable for portable biochemical detection of bio-molecules. The methodology and system, which has been developed in this work, can be extended to generic bio-molecule detection and analysis systems by replacing antibody/antigen with appropriate bio receptors/reagents such as DNA fragments or oligonucleotides for application towards DNA analysis and/or high throughput protein analysis.