In a complex field such as bio-molecular diagnostics it is significant to know the behaviour of molecules in each assay before they are available for real time testing on devices. With numerous deadly diseases around mankind, behaviour of bio-molecules associated with each of these diseases becomes a first priority for the molecular diagnostics. The purpose of this review is to highlight the behaviour of enzymatic molecules using vibrations in conjunction with Micro-Electro-Mechanical Systems (MEMS) structures, which can be used as a diagnostic tool in a rapidly growing field of medical discipline. The authors introduce piezo-electric actuators in the experimental set-up that is used to accelerate the enzymatic molecular reaction in minute quantities of the reactant. The discussion for the above method is well supported by a body of literature from both biomedical and mechanical engineering. These enzymes are made to interact with their respective anti-bodies, whose reaction can be detected using many methods among which fluorescence spectroscopy is of preference and further detected using specific MEMS structures whose changes are detected through optical means. The results described here are intended to give a methodological approach to the creation of device in the future in the medical field for the detection of bio-molecules. Experimental results include pictures taken during shaking with piezo-electric stacks; fluorescence spectrometer results confirming a reaction between the enzyme and its anti-body and the biochemical reaction-taking place on the surface of the cantilever beams. The intent of this review is to better understand the behaviour of an enzymatic molecule under the influence of vibrations. With insight into the principles underlying the operation of the vibration experiment, the results could help to evaluate the value of a device that could be used in the molecular diagnostics in a simpler, faster and less expensive way.
This paper presents modeling, design, and prototyping of a z-axis micro-platform actuator fabricated by MicraGEM (Micralyne GEneralized MEMS) process. With 4 crossly arranged rotational serpentine springs and 12 μm of gap between the circular disk and the bottom electrode underneath it, this platform demonstrates its simple actuation, easy control and capability of fine tuning the vertical displacement in the range of 0.5 μm to 3.0 μm through varying the applied electrical bias. Positioning sensitivity and repeatability of the platform with respect to the applied voltage have been estimated and verified by mathematical model. With proper selection of springs and their geometric parameters, high sensitivity of the z-axis platform actuators can be obtained. The proposed electrostatically actuated micro-platform will gain importance in micro-positioning for optical MEMS and microphotonic devices.
Medical applications often require the detection of specific peptides that are indicators of patients' specific medical conditions. The identification of such peptides is to some extent cumbersome and requires specialized equipment, specialized personnel and the results of the test may come as false negative or false positive. This paper presents the experimental results that directed towards the developments of a device and measurement system that is precisely detecting the reaction time between a peptide and a corresponding reaction match. A series of reaction signatures are identified and presented in the paper. Besides, SEM analysis of the peptides after the reaction confirms the existence of the signatures as the ones recorded by the authors. The proposed device could be miniaturized and a potential solution of the optical-based measurement system is presented and discussed. Serious challenges such as packaging or peptide manipulation are also discussed. The configuration of the sensing element is essential in producing the desired sensitivity of the device. A sensitivity analysis is carried out to prove that concentrations of fraction of ppm are detectable through this method.
Diagnosis and monitoring of critical diseases such as acute myocardial infarction (AMI) require a quantitative analysis of biological molecules. A high-throughput identification of these biological molecules can be generated by using micro-electro-mechanical systems (MEMS) structures like simple cantilever beams, which respond to the intermolecular forces resulting from binding these molecules. Biochemical markers like troponin C are considered the primary markers for myocardial injury and have generated considerable interest. A 26-residue lytic membrane protein of bee venom melittin (ME) is chosen to interact with rabbit skeletal muscle troponin C (TnC) on the surface of the cantilever beams. An optical beam deflection method is employed to identify the enzymatic reaction on the surface of the cantilever due to these proteins. Identification of these proteins is also done using fluorescence spectroscopy (FS) to compliment the optical monitored deflection method. A second set of proteins like horse raddish peroxide (HRP) and hydrogen peroxide (H2O2) are applied to atomic force microscopy (AFM) cantilever beams to study their behavior under the enzymatic reactions of proteins. Identification of these proteins is done using Fourier transform infrared spectroscopy (FTIR). An analytical model of the cantilever beam is developed, and its mode shapes are studied by employing orthogonal polynomials in the classic Rayleigh-Ritz method. The surface stress caused by the enzymatic reaction of the proteins that leads to pure bending on the top surface of the cantilever is evaluated. The information provided by the experimental and analytical modeling reported in this work will be useful in the development of a portable biosensor for the detection of AMI.
Miniaturization and highly accurate detection technologies are key factors to advancing sensor performance and utility and the search for such technologies promises accomplishments with the advent of Micro Electro Mechanical Systems (MEMS) structures. MEMS is an enabling technology that can create integrated devices with mechanical, optical and electronic components. One of the fields where these micro-devices are successfully widespread is that of medical care where micro-machined cantilever sensors are found to be the ideal candidates for bio-sensing applications. These micro-machined cantilevers have been proposed as mechanical transducers for different sensing applications. These sensing surfaces are of interest in the development of novel cantilever-based biosensors. The fascinating aspect about these transducers is that they bend due to modifications in nano-mechanical interactions between neighboring molecules which curve the beam and that curvature can be optically detected. In this paper, PVDF-cantilevers are coated with 2 sets of antibody and antigen on one side, which respond with specific deflection signatures to each other and their intermolecular nano-mechanics bend the cantilever. The first set of antibody and antigen used here are rabbit skeletal muscle Troponin C (TnC) and Honey Bee Venom Melittin (ME) prepared in 50mM KCl and 50mM Tris-HCl buffer at a pH of 7.5 in a 1:1 ratio. The next set used were Horse Raddish Peroxide (HRP) and Hydrogen Peroxide (H2O2) prepared to get 10mg per 1ml of 0.1M Potassium Phosphate dibasic (K2HPO4) and diluted hydrochloric acid to get pH of 6.0. The optical system includes a laser source and a Position Sensitive Detector (PSD) which is used to readout deflections of the PVDF-cantilevers. The behavior of the cantilevers was also monitored with the enzymes under the influence of voltage. The classical problem of evaluating the tip deflection of the cantilever beam is analyzed involving the relation between movement recorded by the PSD, the tip deflection and angle of incidence. The combined results provide valuable information on the development of an optimizing sensing element that would enable life saving treatments of patients suffering from Acute Myocardial Infarction (AMI).
The static and dynamic characteristics of micro-electro-mechanical-systems (MEMS) can be influenced through the application of an electrostatic field or thermal gradient. Both of these mechanisms will affect the performance of the MEMS device significantly. The thermal effects manifest themselves by varying the structural characteristics, Young's modulus of elasticity of the waveguide structure, and the material properties. These types of influences will affect the mechanical integrity through an increase in the flexibility leading to variations in the static deflections and also to the dynamic frequency eigenvalues, and changes to the device geometry can lead to faulty measurements where capacitive sensing is employed. Hence, thermal variations in the operating environment can result in unwanted thermal noise and degradation of signal integrity.
Electrostatic fields or forces can be used to correct for thermal influences, for example, or as stand-alon microsystem performance tuners. The corrector characteristics can be achieved by the integration of a suspended electrode over the waveguide, for example where the induced electrostatic stiffness is aligned with the mechanical stiffness of the waveguide and are opposite in direction to the thermally induced "softening". The "stand-alone" characteristics of an applied electrostatic field can be used to selectively deflect the waveguide through an applied bias voltage and hence the static and dynamic performance can be trimmed or tuned by the application of an electrostatic field. This paper presents an experimental and theoretical investigation into coupled thermo-electrical influences on a microcantilever structure. These combined influences are typical of the operating characteristics and environments of microsystems currently in use.
Micro-electro-mechanical systems (MEMS) by definition are coupled electrical and mechanical microsystems. Additionally, microfabrication tolerances, device geometry and thermal effects, for example, will further cloud the performance characteristics. Hence, the consolidation of these individual parameters into a single output based upon "forward-step" modeling will allow for a complete performance characterization in a manner where changes to the static and dynamic outputs are monitored in a step wise fashion through the addition of the individual parameters separately. This deterministic approach aims to synthesize the "parameter-matrix" under which the microsystem is constrained, both by device design and by the eventual operating conditions. The theoretical modeling of the synthesized parameters into an output determinant would be a valuable design tool especially when targeting specific performance characteristics at the design stage of the microsystem that are tied to both the device design and operating conditions. This paper presents a method for microsystem performance modeling based on the solution of a parameter-matrix into a deterministically synthesized output response. The mathematical modeling is based upon the Rayleigh-Ritz energy method using boundary characteristic orthogonal polynomials. The synthesized output models the static and dynamic response of the step-forward addition of individual microsystem parameters, which when they have been evaluated can be used to specify design criteria under a given set of operating conditions. This analysis method will not only allow the designers of microsystems to determine the influence of intrinsic and extrinsic limitations and conditions, but also to establish viable MEMS platforms based on predetermined output performance characteristics.
One of the major goals of biosensor technology is to detect and quantify in detail analytes with very high accuracy. To achieve this, much of the emphasis in sensor fabrication has been laid on antibody-antigen interaction. The consequence of this focus of enzyme biosensor studies is the development of critical techniques which can be extended in the detection of Acute Myocardial Infarction (AMI). Biosensors for AMI have attracted considerable interest in the last few years since the monitoring of a specific substance is central in enzymatic reactions. This interest has led to the investigation of biochemical markers of myocardial injury. These biomarkers facilitate the diagnosis and treatment of patients with AMI. Serial measurements of biochemical markers are now universally accepted as an important determinant in AMI diagnosis. Due to their high sensitivity and specificity over other biomarkers, the troponins are the markers of choice for the diagnosis or exclusion of AMI. The present techniques used in the identification of the troponins are lengthy and require large amount of specimen solution. The present research is directed towards the identification of optical detection procedures that are compatible to the miniaturization. In the present study an effort has been made to study the antigen-antibody reaction of rabbit skeletal muscle troponin C (TnC) and bee venom melittin (ME). Fluorescence energy transfer experiments were done to investigate the Ca 2+ -dependant interaction of TnC-ME in a 1:1 complex. Experiments were also conducted on TnC-ME binding at different ratios. These results validate the biosensor technology and illustrate how a biosensor can be developed based on the study of interaction between monoclonal antibody and antigen reaction in real time. The reported experimental results provide valuable information that will be useful in the development of a biosensor for the detection of AMI.
A simple and novel way of attenuation is presented to investigate the feasibility of affecting the coupling cylindrical waveguides. Piezoelectric polymers such as PVDF (Poly Vinyledene Fluoride) are very attractive for many applications as they exhibit good piezoelectric and pyroelectric responses and low acoustic impedance. Moreover, their properties can be tailored according to the desired requirements. PVDF actuators are proposed because of their low cost and simple process of fabrication. In this paper, cylindrical waveguides are actuated by means of a piezoelectric actuator using PVDF (Poly Vinylidene Fluoride) material. The presented results include the design and analysis of a new cylindrical waveguide based attenuator with PVDF actuation. The presented results include the influence of PVDF (Poly Vinylidene Fluoride) actuation on the optical coupling efficiency. The paper also includes the parametric study on the variation of the geometry of PVDF film with respect to the coupling efficiency. The results also include the variation of deflection and power loss through cylindrical waveguides for various applied voltages. The paper demonstrates a simple and novel application of PVDF film for optical microsystem.
This paper describes the design of a novel electrostatically actuated optical attenuator that uses the electrostatic actuation of a cylindrical waveguide. The optical MEMS device consists of an electrostatically actuated waveguide positioned in a V-groove and overhanging at the end to act as a cantilever. The optical fiber waveguide can be sputtered with a thin film of gold that acts as a good electrode. The electrostatic force between the electrodes actuates the input fiber under the application of a voltage and causes misalignment between the input and output fibers and thereby attenuates the amount of light transmitted to the output fiber. Electrostatic modeling of the system presented in this paper is simple and sufficiently accurate. The proposed analytical model takes into consideration the geometry of the cylindrical electrodes. The geometrical relationship of the cantilever beam to the range of the biasing voltage is also discussed. The paper presents the variation of deflection of the waveguide and the variation of power loss with respect to the applied voltages. The obtained results clearly demonstrate the efficient use of the proposed method and modeling approach.
This paper explores a novel way of sensing the angular velocity rate change of MEMS based gyroscopes with optical methods. In the capacitive sensing mechanism, displacement due to angular rate induces differential capacitance, requiring many supporting filtering and amplification sub-systems and circuits in the device to eliminate the noise. One of the most important aspects of using optical sensing elements with MEMS technology is the elimination of capacitive sensing used in conventional MEMS based gyroscopes. Conventional bulky optical gyroscopes based on Sagnac effect, with very small drift-rate parameters, is difficult to be implemented with MEMS technology due to the requirement of large area enclosed by the laser ring and fiber optic paths. Light interference effect of optical properties can permit the phase shift measurement of the light wavelength. In this paper, the combination of optical and mechanical systems is studied for estimating angular acceleration rate by Coriolis Effect.
Micro-electro-mechanical-systems (MEMS) offer many advantages for sensing a variety of physical parameters such as accceleration, pressure and temperature. Their small size allows them to operate in close proximity where conventional sensors cannot be introduced especially for thermal measurements. Temperature measurement and control is of fundamental importance to the optimal operating conditions of materials and machinery such as gas turbine engines, space exploration, etc. The temperature characterization will allow proper diagnosis of operating conditions and hence the optimization of controls and environment in order to augment performance and useful lifetime. MEMS based thermal measurements will be very useful as they are sensitive to small fluctuations in the operating conditions. Here, this paper proposes a novel MEMS based bimorph optical device as a thermal sensor. The paper includes the theoretical and experimental analysis on the thermal behavior of optical MEMS devices under different geometrical and parametric conditions. The paper also presents the static and dynamic behavior of optical MEMS based devices under different thermal environments. The results obtained verify the validity of the proposed designs for thermal sensing.
Biomedical applications of MOEMS are limited only by the humankind imagination. Precision measurements are minute amounts of biological material could be performed by optical means with a remarkable accuracy. Although available in medical laboratories, such analyzers are making their way directly to the users. Such an example is the test kit to detect the existence of cardiac enzymes in the blood stream. Apart from the direct users, the medical personnel will make use of such tools given the practicality of the kit. In a large proportion of patients admitted to hospital suspected of Acute Myocardial Infarction (AMI), the symptoms and electrocardiographic changes are inconclusive. This necessitates the use of biochemical markers of myocardial damage for correct exclusion or conformation of AMI. New cardiac-specific markers have recently been introduced into the detection of AMI. The cardiac troponins, because of their extraordinary high specificity for myocardial cell injury, have gained particular interest.
Experimental setup involves the use of a rectangle shaped AFM cantilevers, optical lenses, laser source, oscilloscope and a charged coupled device (CCD) to detect the cantilever deflection. When specific biomolecular binding occurs on one surface of a microcantilever beam, intermolecular nanomechanics bend the cantilever, which can be detected optically. Based upon the above concept, troponin I was detected optically by depositing it on the microcantilever containing anti-troponin I. The laser beam was directed on the cantilever and the deflection noted on the CCD.
The control of environmental conditions, such as temperature, pressure, and humidity, are important in many applications ranging from bio-medical to space exploration. Proper humidity control is also important in the conservation of organic materials. Therefore an accurate and sensitive method to characterize the moisture content of the particular environment is of valuable importance.
This paper proposes a humidity sensitive polyimide material as a fiber optic sensor for humidity measurements. The spectral analysis and the intensity of transmitted light through the polyimide sensor will represent the humidity measure. The paper also presents the absorption characteristics of the proposed humidity sensitive material.
The experimental values on the spectral shift and light intensities are measured at different humidity conditions. This paper will also present the feasibility study for using the proposed fiber optic sensor for humidity measurements.
Early enzymatic identification and confirmation is essential for diagnosis and prevention as in the case of Acute Myocardial Infarction (AMI). Biochemical markers continue to be an important clinical tool for the enzymatic detection. The advent of MEMS devices can enable the use of various microstructures for the detection of enzymes. In this study, the concept of MEMS is applied for the detection of enzyme reaction, in which microcantilevers undergo changes in mechanical behavior that can be optically detected when enzyme molecules adsorb on their surface. This paper presents the static behavior of microcantilevers under Horse Radish Peroxide (HRP) enzyme reaction. The reported experimental results provide valuable information that will be useful in the development of MEMS sensors for enzymatic detection. The surface stress produced due to enzyme reactions results in the bending of cantilevers as similar to the influencing of thermal stress in the cantilevers. This paper also reports the influence of thermal gradient on the microcantilevers.
Modeling, manipulating and testing of the dynamic performances of micro-electro-mechanical systems (MEMS) devices are very important in building successful microsystems. However, MEMS devices pose several significant difficulties in characterization. The physical dimensions of MEMS devices are such that conventional measurement and characterization techniques cannot be used since the sensor would interfere with the measurement. Hence, non-contact sensing systems offer many advantages for MEMS characterization. One important issue in characterizing and troubleshooting MEMS devices is the differentiation between electrical and mechanical effects. By definition, MEMS devices are comprised of electrical and mechanical components forming integrated electro-mechanical systems. The dynamic response of these devices is often difficult to determine because of the coupled electro-mechanical behavior. It is also known that the dynamic response is influenced by the limitation of fabrication processes and the material conditions. Hence, this paper proposes a simpler method to verify the dynamic behavior of MEMS structures using Laser Doppler Velocimeter (LDV). Non-contact vibration measurements are thus possible with such a testing system that can lead to significant improvements in the accuracy and precision of MEMS testing. The dynamic experiments are conducted on different devices and the test results are compared with prediction.
This paper presents and applies the concept of micro-boundary conditioning to the design synthesis of microsystems in order to quantify the influence of inherent limitations of the fabrication process and the operating conditions on both static and dynamic behavior of microsystems. The predicted results on the static and dynamic behavior of a capacitive MEMS device, fabricated through MUMPs process, under the influence of the fabrication limitation and operating environment are presented along with the test results. The comparison between the predicted and experimental results shows a good agreement.
Measurement of acoustic intensity provides information not only on the sound intensity level at the point but on the direction of sound propagation also. Acoustic intensity calculation needs the pressure information and pressure gradient information at a point. Pressure gradient at a point is obtained using pressure measurements from two closely spaced microphones and employing finite difference technique. Presently, two condenser microphones placed at a small distance apart are used for acoustic intensity measurements. These transducers require a pre-amplifier and a signal processing unit making the assembly cumbersome and possibly interfering with the sound field in view of their size. Micromachined sensors are ideal under these circumstances in view of their miniature size, low cost, high reliability and the convenience of heaving the signal processing circuitry in the same microchip close to the sensor.
This paper presents evidence of the influence of the state of stress on anisotropic etching of (100) oriented Si in KOH water solution. External load is applied to strips of Si which modifies the initial internal stress state actually generated by a patterned SiO2 masking film. Results obtained for circular patterns indicate that the etch patterns on the strips subjected to negative and positive stresses are different from each other and are different from strips which have not been subjected to external loads. These observations indicate that the etching process is influenced by the presence of stresses in the silicon. A technique to analyze the stress is proposed. The resulting variations of etched features with applied stress is significant.
The paper presents the process planning and scheduling of two types of micromachined capacitive transducers for pressure measurements. The fabrication process includes micromachined silicon and glass components. The different stages, process parameters and the required time to obtain devices with flat and corrugated membranes, are presented. The information generated from a laboratory scale experiment is extended to an industrial system. A process that involves the manufacturing of 4,800 devices once on 100 three-layer sandwich structures is studied. A total of 47 activities and 9 alternate operations are identified. For each of them, the time period is established using the acquired experience of the laboratory process. All the techniques and their parameters, the resources are screened and the time necessary to accomplish the above mentioned devices, starting from the si and glass wafers are determined. The activities are considered according to their priorities and two process networks are considered for the two types of devices for flat plate and for corrugated plate. The critical activities and the necessary resources at each step are established. An optimum activities' scheduling for the processes is proposed, in which the priorities and the critical processes are identified. The resource allocations and their capacity are also determined.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.