144 research outputs found
Microfabrication and Applications of Opto-Microfluidic Sensors
A review of research activities on opto-microfluidic sensors carried out by the research groups in Canada is presented. After a brief introduction of this exciting research field, detailed discussion is focused on different techniques for the fabrication of opto-microfluidic sensors, and various applications of these devices for bioanalysis, chemical detection, and optical measurement. Our current research on femtosecond laser microfabrication of optofluidic devices is introduced and some experimental results are elaborated. The research on opto-microfluidics provides highly sensitive opto-microfluidic sensors for practical applications with significant advantages of portability, efficiency, sensitivity, versatility, and low cost
Evaluation of Miniaturized Mixer and Integrated Optical Components for Cell Sorting
Conventional cell cytometers are often bulky and thus not convenient for bio-medical analysis where portable devices are desired. They also suffer from the drawback of high cost due to the complicated and expensive optical detection system involved. Therefore miniaturizing conventional cell cytometer is highly demanded as it offers an opportunity to transform the conventional bulky systems to more cost-efficient and portable microfluidic cell sorting devices. In addition to the advantages reduced cost and enhanced portability, microfluidic cell sorting devices require only a tiny amount of sample for analysis. In this thesis, one common microfluidic cell sorting device is developed using similar conventional functions and concepts but different sorting method. Unlike most of the conventional cell cytometers in which an electrical field or magnetic field is employed to deflect the charged target cells to the collecting container, microfluidic cell sorting devices use the fluid flow to control the movement of the targeted cells to the collecting reservoir. By using an electroosmitic pump, the response time of the flow switch is significantly lowered, leading to a much higher sorting efficiency. Despite the advantages of microfluidic cell sorting devices, there are some issues need to be addressed before realization of such devices. For example, more studies are required on the successful integration of the optical elements in the devices. In microfluidic, the transport phenomena is also different from that in macroscopic. Unlike that in macroscopic, surface forces are important in microfluidics. They result in pressure-induced flow which gives the parabolic profile of the velocity along the channel. Also, a plug-like velocity which is generated by the electoosmitic flow is required for the more controllable and accurate detection. To suppress the pressure-driven flow, hydro-resistance elements (Shallow channel network) are implemented on the microfluidic devices. Fabrication of optical elements by deposition of optical materials on glass or silicon wafer has been reported. However, this Micro Electro-Mechanical (MEM) technique requires special equipment and cleanroom facilities used in the semiconductor industry. A good alternative to the MEMS technique is soft lithography where optical elements can be created using polymers. In this work, ultraviolet-sensitive photo resists SU8 is used to fabricate the microfluidic cell sorting devices and the optical elements. By using the mask with the patterns of the microchannel network and optical elements, the optical elements can be fabricated with the microchannel, eliminating the problem of alignment. Experiments are also conducted to evaluate the integrated optical elements. To prevent cross-contamination, samples are usually prepared and are only mixed inside the microfluidic devices by the embedded mixers. Such embedded mixers, however, pose a great challenge as the small characteristic length of a microfluidic device tends to give a laminar flow and diffusion-dominated mixing. A simple passive micromixer is investigated to find the possibilities to integrate it to the microfluidic devices. To truly understand the diffusional mixing, a Y channel mixer is studied through the numerical and experimental investigations. Based on the results found, a possible design is also proposed and evaluated by experiments
Advances in Optofluidics
Optofluidics a niche research field that integrates optics with microfluidics. It started with elegant demonstrations of the passive interaction of light and liquid media such as liquid waveguides and liquid tunable lenses. Recently, the optofluidics continues the advance in liquid-based optical devices/systems. In addition, it has expanded rapidly into many other fields that involve lightwave (or photon) and liquid media. This Special Issue invites review articles (only review articles) that update the latest progress of the optofluidics in various aspects, such as new functional devices, new integrated systems, new fabrication techniques, new applications, etc. It covers, but is not limited to, topics such as micro-optics in liquid media, optofluidic sensors, integrated micro-optical systems, displays, optofluidics-on-fibers, optofluidic manipulation, energy and environmental applciations, and so on
A Customer Programmable Microfluidic System
Microfluidics is both a science and a technology offering great and perhaps even revolutionary capabilities to impact the society in the future. However, due to the scaling effects there are unknown phenomena and technology barriers about fluidics in microchannel, material properties in microscale and interactions with fluids are still missing. A systematic investigation has been performed aiming to develop A Customer Programmable Microfluidic System . This innovative Polydimethylsiloxane (PDMS)-based microfluidic system provides a bio-compatible platform for bio-analysis systems such as Lab-on-a-chip, micro-total-analysis system and biosensors as well as the applications such as micromirrors. The system consists of an array of microfluidic devices and each device containing a multilayer microvalve. The microvalve uses a thermal pneumatic actuation method to switch and/or control the fluid flow in the integrated microchannels. It provides a means to isolate samples of interest and channel them from one location of the system to another based on needs of realizing the customers\u27 desired functions. Along with the fluid flow control properties, the system was developed and tested as an array of micromirrors. An aluminum layer is embedded into the PDMS membrane. The metal was patterned as a network to increase the reflectivity of the membrane, which inherits the deformation of the membrane as a mirror. The deformable mirror is a key element in the adaptive optics. The proposed system utilizes the extraordinary flexibility of PDMS and the addressable control to manipulate the phase of a propagating optical wave front, which in turn can increase the performance of the adaptive optics. Polydimethylsiloxane (PDMS) has been widely used in microfabrication for microfluidic systems. However, few attentions were paid in the past to mechanical properties of PDMS. Importantly there is no report on influences of microfabrication processes which normally involve chemical reactors and biologically reaction processes. A comprehensive study was made in this work to study fundamental issues such as scaling law effects on PDMS properties, chemical emersion and temperature effects on mechanical properties of PDMS, PDMS compositions and resultant properties, as well as bonding strength, etc. Results achieved from this work will provide foundation of future developments of microfluidics utilizing PDMS
Microelectromechanical Systems and Devices
The advances of microelectromechanical systems (MEMS) and devices have been instrumental in the demonstration of new devices and applications, and even in the creation of new fields of research and development: bioMEMS, actuators, microfluidic devices, RF and optical MEMS. Experience indicates a need for MEMS book covering these materials as well as the most important process steps in bulk micro-machining and modeling. We are very pleased to present this book that contains 18 chapters, written by the experts in the field of MEMS. These chapters are groups into four broad sections of BioMEMS Devices, MEMS characterization and micromachining, RF and Optical MEMS, and MEMS based Actuators. The book starts with the emerging field of bioMEMS, including MEMS coil for retinal prostheses, DNA extraction by micro/bio-fluidics devices and acoustic biosensors. MEMS characterization, micromachining, macromodels, RF and Optical MEMS switches are discussed in next sections. The book concludes with the emphasis on MEMS based actuators
BioMEMS
As technological advancements widen the scope of applications for biomicroelectromechanical systems (BioMEMS or biomicrosystems), the field continues to have an impact on many aspects of life science operations and functionalities. Because BioMEMS research and development require the input of experts who use different technical languages and come from varying disciplines and backgrounds, scientists and students can avoid potential difficulties in communication and understanding only if they possess a skill set and understanding that enables them to work at the interface of engineering and biosciences. Keeping this duality in mind throughout, BioMEMS: Science and Engineering Perspectives supports and expedites the multidisciplinary learning involved in the development of biomicrosystems. Divided into nine chapters, it starts with a balanced introduction of biological, engineering, application, and commercialization aspects of the field. With a focus on molecules of biological interest, the book explores the building blocks of cells and viruses, as well as molecules that form the self-assembled monolayers (SAMs), linkers, and hydrogels used for making different surfaces biocompatible through functionalization. The book also discusses: Different materials and platforms used to develop biomicrosystems Various biological entities and pathogens (in ascending order of complexity) The multidisciplinary aspects of engineering bioactive surfaces Engineering perspectives, including methods of manufacturing bioactive surfaces and devices Microfluidics modeling and experimentation Device level implementation of BioMEMS concepts for different applications. Because BioMEMS is an application-driven field, the book also highlights the concepts of lab-on-a-chip (LOC) and micro total analysis system (ÎĽTAS), along with their pertinence to the emerging point-of-care (POC) and point-of-need (PON) applications
Optofluidic components for biomedical applications
In the last years the term Optofluidics has popped up in a large amount of scientific publications. The goal of this thesis is to prove Optofluidics as an applicable, powerful tool for distinct biological and medical applications. In the main part of this work, an optofluidic sensing unit for the determination of liquid concentration is presented. In an experimental evaluation, the sensor was tested with different dissolved molecules including phosphate and lactose. Depending on the analyte, a smallest detectable change in concentration of 10 to 40mmol/L was determined. Besides the sensing device, a new subfield of optofluidics was introduced for the very first time. Thermo-optofluidics deals with the integration of thermal elements in optofluidic systems. Compared to solely solid based realizations more than twice the theoretical switching frequency can be achieved. In conclusion, the applicability of optofluidics for different sensor as well as actuator systems was experimentally proven. All the devices were fabricated applying low-cost, rapid-prototyping fabrication techniques which allow the realization of cost-effective hand-held devices
Opto-microfluidic devices with femtosecond laser microfabrication
Opto-microfluidics is a novel technology that integrates optical devices and systems with microchannels to investigate the properties of fluids. Opto-microfluidic devices have been increasingly recognized as important miniaturized devices for optical measurements, biological analyses, and chemical syntheses. These devices significantly reduce reagent consumption, waste production, analysis time and labour costs. Common fabrication techniques include soft lithography, microelectromechanical systems (MEMS) and hot embossing.
In this dissertation, opto-microfluidic devices fabricated by two-photon polymerization (TPP) technique with femtosecond lasers and standard soft lithography are proposed. After analyzing the fabrication properties of the femtosecond laser, we choose optimal parameters to fabricate optical structures in photoresist material SU-8, and integrate them with microchannels which are produced by a standard soft lithographic technique. Diffractive grating, Mach-Zehnder interferometer (MZI) and optical microring resonators based refractive index (RI) and temperature sensors are designed, fabricated and demonstrated. The sensitivities in different conditions are thoroughly investigated. By combining fluid mechanics and optics, two functional opto-microfluidic devices realizing simultaneous particle sorting and RI sensing are successfully proved. In these devices, filters fabricated by femtosecond lasers are used to sieve and control the flow of particles in suspension, and then the purified liquid is induced into the optical structures to measure the RI. The opto-microfluidic devices described in this dissertation verify the practicability and effectiveness as a lab-on-a-chip platform
BioMEMS
As technological advancements widen the scope of applications for biomicroelectromechanical systems (BioMEMS or biomicrosystems), the field continues to have an impact on many aspects of life science operations and functionalities. Because BioMEMS research and development require the input of experts who use different technical languages and come from varying disciplines and backgrounds, scientists and students can avoid potential difficulties in communication and understanding only if they possess a skill set and understanding that enables them to work at the interface of engineering and biosciences. Keeping this duality in mind throughout, BioMEMS: Science and Engineering Perspectives supports and expedites the multidisciplinary learning involved in the development of biomicrosystems. Divided into nine chapters, it starts with a balanced introduction of biological, engineering, application, and commercialization aspects of the field. With a focus on molecules of biological interest, the book explores the building blocks of cells and viruses, as well as molecules that form the self-assembled monolayers (SAMs), linkers, and hydrogels used for making different surfaces biocompatible through functionalization. The book also discusses: Different materials and platforms used to develop biomicrosystems Various biological entities and pathogens (in ascending order of complexity) The multidisciplinary aspects of engineering bioactive surfaces Engineering perspectives, including methods of manufacturing bioactive surfaces and devices Microfluidics modeling and experimentation Device level implementation of BioMEMS concepts for different applications. Because BioMEMS is an application-driven field, the book also highlights the concepts of lab-on-a-chip (LOC) and micro total analysis system (ÎĽTAS), along with their pertinence to the emerging point-of-care (POC) and point-of-need (PON) applications
- …