Motion video image processing (MVIP) method for measuring microfluidic–structure interactions (original) (raw)

PDMS Microcantilever-Based Flow Sensor Integration for Lab-on-a-Chip

IEEE Sensors Journal, 2013

In this paper, a simple practical method is presented to fabricate a high aspect ratio horizontal polydimethylsiloxane (PDMS) microcantilever-based flow sensor integrated into a microfluidic device. A multilayer soft lithography process is developed to fabricate a thin PDMS layer involving the PDMS microcantilever and the microfluidics network. A three-layer fabrication technique is explored for the integration of the microflow meter. The upper and lower PDMS layers are bonded to the thin layer to release the microcantilever for free deflection. A 3-D finite element analysis is carried out to simulate fluid-structure interaction and estimate cantilever deflection under various flow conditions. The dynamic range of flow rates that is detectable using the flow sensor is assessed by both simulation and experimental methods and compared. Limited by the accuracy of the 1.76-µm resolution of the image acquisition method, the present setup allows for flow rates as low as 35 µL/min to be detected. This is equal to 0.8-µN resolution in equivalent force at the tip. This flow meter can be integrated into any type of microfluidicbased lab-on-a-chip in which flow measurement is crucial, such as flow cytometry and particle separation applications.

Microcantilever: Dynamical Response for Mass Sensing and Fluid Characterization

Sensors

A microcantilever is a suspended micro-scale beam structure supported at one end which can bend and/or vibrate when subjected to a load. Microcantilevers are one of the most fundamental miniaturized devices used in microelectromechanical systems and are ubiquitous in sensing, imaging, time reference, and biological/biomedical applications. They are typically built using micro and nanofabrication techniques derived from the microelectronics industry and can involve microelectronics-related materials, polymeric materials, and biological materials. This work presents a comprehensive review of the rich dynamical response of a microcantilever and how it has been used for measuring the mass and rheological properties of Newtonian/non-Newtonian fluids in real time, in ever-decreasing space and time scales, and with unprecedented resolution.

Evaluation of micromechanical manufacturing processes for microfluidic devices

2010

In this paper several micro-mechanical manufacturing technologies were studied in order to characterize their performance for prototyping miniaturized geometries known as micro-channels, which are the main geometric features of micro-fluidic devices. The technologies used were Micro-End Milling, Wire Electro Discharge Machining/Sandblasting and Abrasive Water Jet.

Fabrication of a cantilever-based microfluidic flow meter with nL min-1 resolution

Journal of Micromechanics and Microengineering, 2011

A microfluidic flow meter based on cantilever deflection is developed, showing a resolution down to 3 nL min-1 for flows in the microliter range. The cantilevers are fabricated in SU-8 and have integrated holes with dimensions from 5 × 5 to 20 × 20 µm2. The holes make it possible to measure in a liquid environment. With a lithography optimization,

Geometrical and flow configurations for enhanced microcantilever detection within a fluidic cell

2005

This work focuses on studying the effect of the flow conditions and the geometric variation of the microcantilever's supporting system on the microcantilever detection capabilities within a fluidic cell for various pertinent parameters. Such parameters include Reynolds number, height of the fluidic cell, surface reaction constant, and the Schmidt number. The results of this investigation show that the flow direction has a profound effect on the normal velocity across the microcantilever due to the presence of the supporting mechanism.

Hybrid macro-micro fluidics system for a chip-based biosensor

Journal of Micromechanics and Microengineering, 2002

We describe the engineering of a hybrid fluidics platform for a chip-based biosensor system that combines high-performance microfluidics components with powerful, yet compact, millimeter-scale pump and valve actuators. The microfluidics system includes channels, valveless diffuser-based pumps, and pinch-valves that are cast into a poly(dimethylsiloxane) (PDMS) membrane and packaged along with the sensor chip into a palm-sized plastic cartridge. The microfluidics are driven by pump and valve actuators contained in an external unit (with a volume ∼30 cm 3) that interfaces kinematically with the PDMS microelements on the cartridge. The pump actuator is a simple-lever, flexure-hinge displacement amplifier that increases the motion of a piezoelectric stack. The valve actuators are an array of cantilevers operated by shape memory alloy wires. All components can be fabricated without the need for complex lithography or micromachining, and can be used with fluids containing micron-sized particulates. Prototypes have been modeled and tested to ensure the delivery of microliter volumes of fluid and the even dispersion of reagents over the chip sensing elements. With this hybrid approach to the fluidics system, the biochemical assay benefits from the many advantages of microfluidics yet we avoid the complexity and unknown reliability of immature microactuator technologies.

On-chip characterization of the viscoelasticity of complex fluids using microcantilevers

Measurement Science and Technology, 2012

Due to the need for a microrheometer monitoring the high-frequency viscoelasticity of soft matter in situ, we describe a cantilever-based microrheometer to achieve this purpose. The elastic and viscous moduli of complex fluids can be measured with an acceptable accuracy over a high frequency bandwidth of 1-100 kHz. Some preliminary data on small samples (~10-100 μL) of simple Newtonian and viscoelastic polymer and surfactant solutions showed the ability to measure the dynamic moduli in the range of 0.01-10 kPa. This approach will provide a new way to characterize in situ, dynamic microrheology of minute and trace materials and will advance the field of biorheology, microfluidics, and polymer processing.

Parametric study on fluid structure interaction of a 3D suspended polymeric microfluidics (SPMF3)

Microsystem Technologies-micro-and Nanosystems-information Storage and Processing Systems, 2018

Embedding microfluidic channel inside a microcantilever has drastically improved the sensitivity of microcantilever biosensors. The sensing principles in suspended microfluidics have been either stress induced deflections or mass based frequency variations. However, the suspended microfluidics can be designed to use flow forces as the sensing principle. In this study, a 3D suspended polymeric microfluidics (SPMF 3) is designed with flow plane orthogonal to bending plane. This design innovation, enables the SPMF 3 to detect physical properties of bioelements through microcantilever deflections induced by flow force variations inside the embedded suspended microfluidics. Here, the earlier approaches in design and modeling of suspended microfluidics are presented and explained in detail. First, a 2D suspended microfluidics is modeled and its sensitivity to flow forces is analyzed. Modifying the microchannel plane position with respect to cantilever neutral plane results in different microcantilever deflections and consequently biodetection sensitivity. In order to verify the concept of the 3D suspended polymeric microfluidics (SPMF 3) for physical study of bioelements, first, a finite element analysis (FEA) of a sample flow inside the microfluidic system is performed. In this modeling, microfluidic-microcantilever interactions and the system sensitivity to flow forces are studied. The SPMF 3 deflections with different aperture design is modeled and the sensitivity of each design is analyzed. Three different types of apertures namely, straight aperture, nozzle and diffuser have been modeled and the results show that the diffuser aperture has better sensitivity to flow forces under same working conditions. According to the FEA results, flow force can be employed as a sensing principle of 2D suspended microfluidics. However, sensitivity of the 3D suspended microfluidics is drastically increased and can be tuned for any specific biodiagnostic application using different aperture designs.

Image Analysis of Microfluidics: Visualization of Flow at the Microscale

2013 ASEE Annual Conference & Exposition Proceedings

Microfluidics is the study and application of fluid flow at the microscale. As a representative example, many microfluidic devices and systems are based on a polymer substrate ('chips') in which a miniaturized fluidic network of channels, conduits, chambers, filters, packed beds, valves, and fluid actuators is fabricated using various prototyping methods. Feature sizes (e.g., channel widths) range from 0.1 to several millimeters. Fluid actuation and flow control can be effected by a number of different mechanisms to implement a process comprised of metering, heat transfer, mixing, reaction, and separation steps, monitored with sensors such as pressure gauges, thermocouples, RTDs, and photodetectors. Furthermore, fluid flow in the chips is highly amenable to image capture, processing, and analysis using visible and thermal (infrared) cameras. The interdisciplinary nature of microfluidics, its relative low cost and accessible technology, and its importance in emerging technologies suggest a wider use of microfluidicsbased systems in engineering education. Our aims are to develop a series of microfluidics-based experiments to demonstrate concepts in fluid mechanics and heat/mass transfer, as well as develop student skills in CAD, prototyping, sensors, instrumentation and control, and image analysis. Chips can be designed, fabricated, and operated in time frames of hours, and such projects provide students with an opportunity for conceptualization, design, prototyping, implementation, and analysis of fluidic and thermal systems in a readily accessible and easilyinterpretable format. Here we report approaches and techniques to provide resources for instruction and experimentation in microfluidics-based fluid mechanics, with emphasis on characterizing various flow modes with image capture, processing, and analysis.

Piezoresistive cantilever based nanoflow and viscosity sensor for microchannels

2006

Microfluidic channels are microreactors with a wide range of applications, including molecular separations based upon micro/nanoscale physicochemical properties, targeting and delivery of small amount of fluids and molecules, and patterned/directed growth. Their successful applications would require a detailed understanding of phenomena associated with the microscale flow of liquids through these channels, including velocity, viscosity and miscibility. Here we demonstrate a highly sensitive piezoresistive cantilever to measure flow properties in microfluidic channels. By milling down the legs of the piezoresistive cantilevers, we have achieved significantly higher mechanical sensitivity and a smaller spring constant, as determined by AFM. These cantilevers were used in microchannels to measure the viscosity and flow rate of ethylene glycol mixtures in water over a range of concentrations, as well as of low viscosity biologically relevant buffers with different serum levels. The sensor can be used alone or can be integrated in AFM systems for multidimensional study in micro and nanochannels.