Magnetic forces are now being utilised in an amazing variety of microfluidic applications. Magnetohydrodynamic flow has been applied to the pumping of fluids through microchannels. Magnetic materials such as ferrofluids or magnetically doped PDMS have been used as valves. Magnetic microparticles have been employed for mixing of fluid streams. Magnetic particles have also been used as solid supports for bioreactions in microchannels. Trapping and transport of single cells are being investigated and recently, advances have been made towards the detection of magnetic material on-chip. The aim of this review is to introduce and discuss the various developments within the field of magnetism and microfluidics.

Magnetism and microfluidics

Micro total analysis systems. Recent developments.

Part I: Background and Fundamentals Introduction, Mohamed Gad-el-Hak, University of Notre Dame Scaling of Micromechanical Devices, William Trimmer, Standard MEMS, Inc., and Robert H. Stroud, Aerospace Corporation Mechanical Properties of MEMS Materials, William N. Sharpe, Jr., Johns Hopkins University Flow Physics, Mohamed Gad-el-Hak, University of Notre Dame Integrated Simulation for MEMS: Coupling Flow-Structure-Thermal-Electrical Domains, Robert M. Kirby and George Em Karniadakis, Brown University, and Oleg Mikulchenko and Kartikeya Mayaram, Oregon State University Liquid Flows in Microchannels, Kendra V. Sharp and Ronald J. Adrian, University of Illinois at Urbana-Champaign, Juan G. Santiago and Joshua I. Molho, Stanford University Burnett Simulations of Flows in Microdevices, Ramesh K. Agarwal and Keon-Young Yun, Wichita State University Molecular-Based Microfluidic Simulation Models, Ali Beskok, Texas A&M University Lubrication in MEMS, Kenneth S. Breuer, Brown University Physics of Thin Liquid Films, Alexander Oron, Technion, Israel Bubble/Drop Transport in Microchannels, Hsueh-Chia Chang, University of Notre Dame Fundamentals of Control Theory, Bill Goodwine, University of Notre Dame Model-Based Flow Control for Distributed Architectures, Thomas R. Bewley, University of California, San Diego Soft Computing in Control, Mihir Sen and Bill Goodwine, University of Notre Dame Part II: Design and Fabrication Materials for Microelectromechanical Systems Christian A. Zorman and Mehran Mehregany, Case Western Reserve University MEMS Fabrication, Marc J. Madou, Nanogen, Inc. LIGA and Other Replication Techniques, Marc J. Madou, Nanogen, Inc. X-Ray-Based Fabrication, Todd Christenson, Sandia National Laboratories Electrochemical Fabrication (EFAB), Adam L. Cohen, MEMGen Corporation Fabrication and Characterization of Single-Crystal Silicon Carbide MEMS, Robert S. Okojie, NASA Glenn Research Center Deep Reactive Ion Etching for Bulk Micromachining of Silicon Carbide, Glenn M. Beheim, NASA Glenn Research Center Microfabricated Chemical Sensors for Aerospace Applications, Gary W. Hunter, NASA Glenn Research Center, Chung-Chiun Liu, Case Western Reserve University, and Darby B. Makel, Makel Engineering, Inc. Packaging of Harsh-Environment MEMS Devices, Liang-Yu Chen and Jih-Fen Lei, NASA Glenn Research Center Part III: Applications of MEMS Inertial Sensors, Paul L. Bergstrom, Michigan Technological University, and Gary G. Li, OMM, Inc. Micromachined Pressure Sensors, Jae-Sung Park, Chester Wilson, and Yogesh B. Gianchandani, University of Wisconsin-Madison Sensors and Actuators for Turbulent Flows. Lennart Loefdahl, Chalmers University of Technology, and Mohamed Gad-el-Hak, University of Notre Dame Surface-Micromachined Mechanisms, Andrew D. Oliver and David W. Plummer, Sandia National Laboratories Microrobotics Thorbjoern Ebefors and Goeran Stemme, Royal Institute of Technology, Sweden Microscale Vacuum Pumps, E. Phillip Muntz, University of Southern California, and Stephen E. Vargo, SiWave, Inc. Microdroplet Generators. Fan-Gang Tseng, National Tsing Hua University, Taiwan Micro Heat Pipes and Micro Heat Spreaders, G. P. "Bud" Peterson, Rensselaer Polytechnic Institute Microchannel Heat Sinks, Yitshak Zohar, Hong Kong University of Science and Technology Flow Control, Mohamed Gad-el-Hak, University of Notre Dame) Part IV: The Future Reactive Control for Skin-Friction Reduction, Haecheon Choi, Seoul National University Towards MEMS Autonomous Control of Free-Shear Flows, Ahmed Naguib, Michigan State University Fabrication Technologies for Nanoelectromechanical Systems, Gary H. Bernstein, Holly V. Goodson, and Gregory L. Snider, University of Notre Dame Index

The MEMS Handbook

Rapid and accurate measurement of biomarkers in tissue and fluid samples is a major challenge in medicine. Here we report the development of a new, miniaturized diagnostic magnetic resonance (DMR) system for multiplexed, quantitative and rapid analysis. By using magnetic particles as a proximity sensor to amplify molecular interactions, the handheld DMR system can perform measurements on unprocessed biological samples. We show the capability of the DMR system by using it to detect bacteria with high sensitivity, identify small numbers of cells and analyze them on a molecular level in real time, and measure a series of protein biomarkers in parallel. The DMR technology shows promise as a robust and portable diagnostic device.

/pdf/chip-nmr-biosensor-for-detection-and-molecular-analysis-of-3h7yxudmsx.pdf

Chip–NMR biosensor for detection and molecular analysis of cells

Significant progress has been made recently in demonstrating that silicon photonics is a promising technology for low-cost optical detectors, modulators and light sources1,2,3,4,5,6,7,8,9,10,11,12. It has often been assumed, however, that their performance is inferior to InP-based devices. Although this is true in most cases, one of the exceptions is the area of avalanche photodetectors, where silicon's material properties allow for high gain with less excess noise than InP-based avalanche photodetectors and a theoretical sensitivity improvement of 3 dB or more. Here, we report a monolithically grown germanium/silicon avalanche photodetector with a gain–bandwidth product of 340 GHz, a keff of 0.09 and a sensitivity of −28 dB m at 10 Gb s−1. This is the highest reported gain–bandwidth product for any avalanche photodetector operating at 1,300 nm and a sensitivity that is equivalent to mature, commercially available III–V compound avalanche photodetectors. This work paves the way for the future development of low-cost, CMOS-based germanium/silicon avalanche photodetectors operating at data rates of 40 Gb s−1 or higher. A monolithically grown Ge/Si avalanche photodetectors (APD) with a gain–bandwidth product of 340 GHz, the highest value for any APDs operating at 1,300 nm, and a sensitivity equivalent to commercially available III-V compound APDs is reported. The excellent performance paves the way to achieving low-cost, CMOS-based, Ge/Si APDs operating at data rates of 40 Gb s−1 or higher, where the performance of III-V APDs is severely limited.

https://www.nature.com/articles/nphoton.2008.247.pdf?proof=t

Monolithic germanium/silicon avalanche photodiodes with 340 GHz gain-bandwidth product

We study driving conditions to improve the extinction ratios in 2/spl times/2 and 1/spl times/2 all-optical switches based on semiconductor optical amplifiers in Mach-Zehnder configuration. In 2/spl times/2 switches, the optimization of the relative phases of both arms of the interferometer together with the introduction of an optical push-pull lead to enhanced and symmetrical extinctions. In 1/spl times/2 switches, perfect extinctions can theoretically be obtained by adapting the splitting ratios of the input and output couplers to the saturation behavior of the amplifiers.

All-optical switches based on Mach-Zehnder configuration with improved extinction ratios

We have realized metallic profile and coin imaging using a miniaturized inductive proximity sensor. The sensor is a microsystem composed of a 1 mm diameter coil and a new ASIC interface based on the principle of a differential relaxation oscillator. We successfully acquired wellrecognizable images of various coins with different geometrical, electrical and magnetic properties. The integration of such sensor microsystems on a line will open the way to fast and safe coin pattern recognition.

Metallic profile and coin imaging using an inductive proximity sensor microsystem

A resolution better than 50 nm has been achieved with a new miniaturized inductive proximity sensor. This sensor microsystem is made of a 1 mm diameter coil connected to a new and highly sensitive ASIC based on a differential relaxation oscillator. Lateral as well as axial resolutions have been characterized. A microsystem for step-motor control with an accuracy better than 2 ° is demonstrated. This application is not affected by the temperature behaviour of the sensor.

High-resolution miniaturized inductive proximity sensor: characterization and application for step-motor control

We analyse the problem of scaling down an inductive proximity sensor made of superposed multiple-turn flat coils. We scale down linearly all the geometrical dimensions. Then the nominal inductance is scaled down proportionally to the scale factor. The coupling factor of the superposed coils remains constant. However, for both ferromagnetic and non-ferromagnetic targets, the sensitivity remains constant when the frequency is scaled by the inverse square of the reduction factor. But the parasitic effects in the sensor coil become more important for small device dimensions. Therefore these effects are expected to set the ultimate limit in the miniaturization of the integrated inductive proximity sensors.

Scaling down an inductive proximity sensor

We present a new type of lateral backward silicon diode intended to be used as a strain sensor. The devices are fabricated using a close-to-conventional silicon technology. The diodes have a prevailing tunnelling current around zero bias. They exhibit a high strain sensitivity and a low temperature coefficient of opposite sign to that of conventional piezoresistors.

P.-A. Besse

Papers

All-optical switches based on Mach-Zehnder configuration with improved extinction ratios

Metallic profile and coin imaging using an inductive proximity sensor microsystem

High-resolution miniaturized inductive proximity sensor: characterization and application for step-motor control

Scaling down an inductive proximity sensor

Lateral backward diodes as strain sensors