Biomicroelectromechanical System Research Articles

Ultrasensitive detection of vital biomolecules based on a multi-purpose BioMEMS for Point of care testing: digoxin measurement as a case study

Rapid and label-free detection of very low concentrations of biomarkers in disease diagnosis or therapeutic drug monitoring is essential to prevent disease progression in Point of Care Testing. For this purpose, we propose a multi-purpose optical Bio-Micro-Electro-Mechanical-System (BioMEMS) sensing platform which can precisely measure very small changes of biomolecules concentrations in plasma-like buffer samples. This is realized by the development of an interferometric detection method on highly sensitive MEMS transducers (cantilevers). This approach facilitates the precise analysis of the obtained results to determine the analyte type and its concentrations. Furthermore, the proposed multi-purpose platform can be used for a wide range of biological assessments in various concentration levels by the use of an appropriate bioreceptor and the control of its coating density on the cantilever surface. In this study, the present system is prepared for the identification of digoxin medication in its therapeutic window for therapeutic drug monitoring as a case study. The experimental results represent the repeatability and stability of the proposed device as well as its capability to detect the analytes in less than eight minutes for all samples. In addition, according to the experiments carried out for very low concentrations of digoxin in plasma-like buffer, the detection limit of LOD = 300 fM and the maximum sensitivity of S = 5.5 × 1012 AU/M are achieved for the implemented biosensor. The present ultrasensitive multi-purpose BioMEMS sensor can be a fully-integrated, cost-effective device to precisely analyze various biomarker concentrations for various biomedical applications.

A practical approach for standardization of converse piezoelectric constants obtained from piezoresponse force microscopy

The ability to reliably measure electromechanical properties is crucial to the advancement of materials design for applications in fields ranging from biology and medicine to energy storage and electronics. With the relentless miniaturization of device technology, the ability to perform this characterization on the nanoscale is paramount. Due to its ability to probe electromechanical properties on the micro- and nano-scales, piezoresponse force microscopy (PFM) has become the premier tool for piezoelectric and ferroelectric characterization of a new generation of smart, functional materials. Despite its widespread use and popularity, PFM is a highly nuanced technique, and measurements on similar samples using different machines and/or in different laboratories often fail to agree. A comprehensive protocol for accurate quantitative measurements has not been presented in the literature, slowing the general uptake of the technique by reducing the ability of research groups to take full advantage of PFM for their characterization needs. Here, we present a procedure for PFM measurements, which outlines the practical aspects of quantitative PFM, from sample preparation to probe choice and use of control samples, and we substantiate these steps with original data on lithium niobate control samples. This quantitative characterization protocol is critical as society looks to smaller, greener alternatives to traditional piezoelectric materials for applications such as drug delivery, bio-microelectromechanical system sensors and actuators, and energy harvesting.

A Measurement Platform for Label-Free Detection of Biomolecules Based on a Novel Optical BioMEMS Sensor

In this article, a novel optical Bio-microelectromechanical system (MEMS) sensing platform is proposed based on a tunable laser and its lasing wavelength to detect the biomolecules and measure their quantities. The present biosensor consists of a BioMEMS cantilever and a proposed external cavity tunable laser. While the target samples (i.e., DNA, mRNA, or protein) are exposed to the cantilever surface, target-analyte bindings are happened. This can induce a surface stress on the MEMS cantilever and results in its bending due to the surface stress difference in each side of the cantilever. Thus, the gap size between the laser cavity and the gain medium is changed which can be measured by the wavelength variations of the proposed tunable laser source. Consequently, by analyzing the output response, one can detect the amount of target biomolecules in the sample and assign a level of contamination, infection, or bioparticles, caused by the specific disease. Various parameters of the proposed device are designed by numerical and analytical approaches. Furthermore, functional characteristics of the present BioMEMS sensor are obtained as follows: mechanical sensitivity of $1.8~\mu \text{m}$ /Nm−1, optical sensitivity of 422 nm/RIU, Q-factor of 610, and resonant frequency of 6.43 kHz. The obtained functional characteristics of the proposed device show that the present optical BioMEMS sensor can be appealing for highly sensitive diagnoses of various types of diseases and their progress level.

Development of Novel Magneto-Biosensor for Sulfapyridine Detection.

In this work, we report the development of a highly sensitive biosensor for sulfapyridine detection based on an integrated bio micro-electromechanical system (Bio-MEMS) containing four gold working electrodes (WEs), a platinum counter electrode (CE), and a reference electrode (RE). Firstly, the cleaned WEs were modified with 4-aminophenylacetic acid (CMA). Then, (5-[4-(amino)phenylsulfonamide]-5-oxopentanoic acid (SA2BSA) was immobilized onto the transducers surface by carbodiimide chemistry. The analyte was quantified by competitive detection with SA2BSA immobilized on the WE toward a mixture of Ab155 antibody (with fixed concentration) and sulfapyridine. In order to obtain a highly sensitive biosensor, Ab155 was immobilized onto magnetic latex nanoparticles surface to create a 3D architecture (Ab-MLNp). Using electrochemical impedance spectroscopy (EIS), we investigated the influence of the Ab-MLNp on the sensitivity of our approach. The optimized system was analyzed, as competitive assay, with different concentrations of sulfapyridine (40 µM, 4 µM, and 2 nM) and with phosphate buffer solution. From data fitting calculations and graphs, it was observed that the EIS showed more linearity when Ab-MLNp was used. This result indicates that the magnetic latex nanoparticles increased the sensitivity of the biosensor.

A CMOS MEMS-based Membrane-Bridge Nanomechanical Sensor for Small Molecule Detection

Small molecule compounds are necessary to detect with high sensitivity since they may cause a strong effect on the human body even in small concentrations. But existing methods used to evaluate small molecules in blood are inconvenient, costly, time-consuming, and do not allow for portable usage. In response to these shortcomings, we introduce a complementary metal-oxide-semiconductor bio-microelectromechanical system (CMOS BioMEMS) based piezoresistive membrane-bridge (MB) sensor for detecting small molecule (phenytoin) concentrations as the demonstration. Phenytoin is one of anticonvulsant drugs licensed for the management of seizures, which has a narrow therapeutic window hence a level of concentration monitoring was needed. The MB sensor was designed to enhance the structural stability and increase the sensitivity, which its signal response increased 2-fold higher than that of the microcantilever-based sensor. The MB sensor was used to detect phenytoin in different concentrations from 5 to 100 μg/mL. The limit of detection of the sensor was 4.06 ± 0.15 μg/mL and the linear detection range was 5–100 μg/mL, which was within the therapeutic range of phenytoin concentration (10–20 μg/mL). Furthermore, the MB sensor was integrated with an on-chip thermal effect eliminating modus and a reaction tank on a compact chip carrier for disposable utilization. The required amount of sample solution was only 10 μL and the response time of the sensor was about 25 minutes. The nano-mechanical MB sensing method with thermal effect compensation is specific, sensitive, robust, affordable and well reproducible; it is, therefore, an appropriate candidate for detecting small molecules.

3C-SiC/Si Heterostructure: An Excellent Platform for Position-Sensitive Detectors Based on Photovoltaic Effect.

Single-crystalline silicon carbide (3C-SiC) on the Si substrate has drawn significant attention in recent years due to its low wafer cost and excellent mechanical, chemical, and optoelectronic properties. However, the applications of the structure have primarily been focused on piezoresistive and pressure sensors, bio-microelectromechanical system, and photonics. Herein, we report another promising application of the heterostructure as a laser spot position-sensitive detector (PSD) based on the lateral photovoltaic effect (LPE) under nonuniform optical illuminations at zero-bias conditions. The LPE shows a linear dependence on spot positions, and the sensitivity is found to be as high as 33 mV/mm under an illumination of 2.8 W/cm2 (635 nm). The structure also exhibits a linear dependence of the LPE over a large distance (7 mm) between two electrodes, which is crucial for PSDs as the region with a linear dependence of LPE is only usable for PSDs. The LPE at different spot positions and under different illumination conditions have been investigated and explained based on the energy-band analysis. The temperature dependence of the LPE and position sensitivity is also investigated. Furthermore, the two-dimensional mapping of the lateral photovoltages reveals the potential for utilizing the 3C-SiC/Si heterostructure to detect the laser spot position precisely on a plane.

Development and application of a novel electrochemical immunosensor for tetracycline screening in honey using a fully integrated electrochemical Bio-MEMS

Tetracycline (TC) is a veterinary drug, wildly prescribed for prophylactic and therapeutic purposes. Consequently, its remaining residues in food products have to be regularized. We report in this paper about the development of a novel immunosensor based on an integrated bio micro-electromechanical system (Bio-MEMS) containing eight gold microelectrodes (µWEs), an integrated silver and platinum reference and counter electrodes, respectively. TC immobilization on the µWEs surface was conducted using three methods. The first through functionalization with 4-aminophenylacetic acid (CMA), the second by functionalization with CMA followed by preconcentration of a new structure of magnetic nanoparticles (MNPs) coated with poly (pyrrole-co-pyrrole-2-carboxylic acid) (Py/Py-COOH/MNPs) cross-linked with Ab-TC, and the last one directly through the functionalization with Py/Py-COOH/MNPs. The analyte was quantified by competitive detection with TC immobilized on the µWEs surface toward specific polyclonal antibody (Ab-TC), using a mixture of a fixed concentration of Ab-TC and decreasing levels of TC one from 0.1 pg mL−1 to 1000 pg mL−1. Microcontact printing, followed by fluorescence microscopy characterization were performed during the functionalization of the immunosensor surface to certify that the corresponding immune detection process is taking place. This immunosensor was found to be highly sensitive with a limit of detection of 1.2 pg mL−1 and specific in the presence of interferents. The standard addition method was exploited to detect TC in honey samples. The present immunosensor platform is up-and-coming for TC detection which can dramatically decrease the time of analysis providing a new pathway for advanced immunoassays development in industrial food control.

Novel strategy for sulfapyridine detection using a fully integrated electrochemical Bio-MEMS: Application to honey analysis

Sulfapyridine (SPy) is a sulfonamide antibiotic largely employed as veterinary drugs for prophylactic and therapeutic purposes. Therefore, its spread in the food products has to be restricted. Herein, we report the synthesis and characterization of a novel electrochemical biosensor based on gold microelectrodes modified with a new structure of magnetic nanoparticles (MNPs) coated with poly(pyrrole-co-pyrrole-2-carboxylic acid) (Py/Py-COOH) for high efficient detection of SPy. This analyte was quantified through a competitive detection procedure with 5-[4-(amino)phenylsulfonamide]-5-oxopentanoic acid-BSA (SA2-BSA) antigens toward polyclonal antibody (Ab-155). Initially, gold working electrodes (WEs) of integrated biomicro electro-mechanical system (BioMEMS) were functionalized by Ppy-COOH/MNPs, using a chronoamperometric (CA) electrodeposition. Afterward, SA2-BSA was covalently bonded to Py/Py-COOH/MNP modified gold WEs through amide bonding. The competitive detection of the analyte was made by a mixture of a fixed concentration of Ab-155 and decreasing concentrations of SPy from 50µgL−1 to 2ngL−1. Atomic Force Microscopy characterization was performed in order to ensure Ppy-COOH/MNPs electrodeposition on the microelectrode surfaces. Electrochemical measurements of SPy detection were carried out using electrochemical impedance spectroscopy (EIS). This biosensor was found to be highly sensitive and specific for SPy, with a limit of detection of 0.4ngL−1. This technique was exploited to detect SPy in honey samples by using the standard addition method. The measurements were highly reproducible for detection and interferences namely, sulfadiazine (SDz), sulfathiazole (STz) and sulfamerazine (SMz). Taking these advantages of sensitivity, specificity, and low cost, our system provides a new horizon for development of advanced immunoassays in industrial food control.

Development of a bio-microelectromechanical system device for axonal extension evaluation by PC12D patterning using a dielectrophoresis method

We developed a bio-microelectromechanical system (bio-MEMS) device by combining the dielectrophoresis (DEP) method and MEMS technology that to trap a single PC12D (rat phenocromocytoma cell) for cell pattern formation to measure the axonal extension function. Our device could trap PC12Ds to assign bicells, with designed distances between two cells of 100, 200, and 300 μm. PC12Ds were injected into our bio-MEMS device using a micropipette. We observed the axonal extension using a time-lapse microscope to study the effect of the bicell distance on the axonal extension and connection ability. An alternative electric field (frequency: 10 MHz, voltage: 5 Vp−p) was applied for the PC12D DEP patterning. To keep the patterned PC12Ds on the electrode holes, water was injected using a microsyringe to sweep out excess cells, which remained outside the holes. An average single PC12D pattern ratio of 89.3% was achieved. The axonal extension ability was affected by the cell distance. PC12D bicell distances of 100 and 200 μm showed good connection ratios of 86.7% and 91.7%, respectively, where as a bicell distance of 300 μm showed a low-connection ratio of about 40.0%. We confirmed the applicability of our bio-MEMS device to bicell patterning and evaluated the cell extension function.

Low-Temperature Silicon-to-Silicon Anodic Bonding Using Sodium-Rich Glass for MEMS Applications

In the present work, silicon-to-silicon anodic bonding has been accomplished using an intermediate sodium-rich glass layer deposited by a radiofrequency magnetron sputtering process. The bonding was carried out at low direct-current voltage of about 80 V at 365°C. The alkali ion (sodium) concentration in the deposited film, the surface roughness of the film, and the flatness of the silicon wafers were studied in detail and closely monitored to improve the bond strength of the bonded silicon wafers. The effect of chemical mechanical polishing (CMP) on the surface roughness of the deposited film was also investigated. The average roughness of the deposited film was found to be ~6 A, being reduced to 2 A after CMP. It was observed that the concentration of sodium ions in the deposited film varied significantly with the sputtering parameters. Scanning electron microscopy was used to obtain cross-sectional images of the bonded pair. The bonding energy of the bonded wafer pair was measured using the crack-opening method. The bonding energy was found to vary from 0.3 J/m2 to 2.1 J/m2 for different bonding conditions. To demonstrate the application of the process developed, a sealed cavity was created using the silicon-to-silicon anodic bonding technique, which can be used for fabrication of devices such as capacitive pressure sensors and Fabry– Perot-based pressure sensors. Also, a matrix of microwells was fabricated using this technique, which can be used in various biomicroelectromechanical system applications.

Sensing glucose concentrations at GHz frequencies with a fully embedded Biomicro-electromechanical system (BioMEMS).

The progressive scaling in semiconductor technology allows for advanced miniaturization of intelligent systems like implantable biosensors for low-molecular weight analytes. A most relevant application would be the monitoring of glucose in diabetic patients, since no commercial solution is available yet for the continuous and drift-free monitoring of blood sugar levels. We report on a biosensor chip that operates via the binding competition of glucose and dextran to concanavalin A. The sensor is prepared as a fully embedded micro-electromechanical system and operates at GHz frequencies. Glucose concentrations derive from the assay viscosity as determined by the deflection of a 50 nm TiN actuator beam excited by quasi-electrostatic attraction. The GHz detection scheme does not rely on the resonant oscillation of the actuator and safely operates in fluidic environments. This property favorably combines with additional characteristics-(i) measurement times of less than a second, (ii) usage of biocompatible TiN for bio-milieu exposed parts, and (iii) small volume of less than 1 mm3-to qualify the sensor chip as key component in a continuous glucose monitor for the interstitial tissue.

Implementation of BioMEMS for Determining Mechanical Properties of Biological Cells

ABSTRACTThis paper describes the implementation of a custom-made bio-microelectromechanical system for determining mechanical properties of biological cells, which is used for the measurement of mechanical properties of fibroblasts. Our system consists of several subcomponents: (a) actuator which deforms the cell in pre-determined, step-wise fashion, (b) force sensor that measures force applied onto the cell, (c) set of dielectrophoretic (DEP) electrodes for positioning cells in the desired position, (d) temperature sensors and (e) heater. Preliminary results of the mechanical properties of NIH3T3 cells have been determined using this tool and our cell compression techniques.

A new transparent Bio-MEMS for uni-axial single cell stretching

A novel, completely transparent bio-MEMS (bio-Micro Electro Mechanical System) device has been devised and manufactured using finite element analysis (FEA) and micro-fabrication techniques. The device has been designed to be used for testing the mechanical properties of single living cells, it is versatile and suitable for coupling with other analysis techniques. Furthermore, being completely transparent, it can be used with either transmission or reflection microscopes. The transparent bio-MEMS is based on a silicon dioxide–silicon nitride structure and, since the main goal is to test living cells, it is meant to work in a liquid environment and allow for cell stretching. Sensors for cell deformation and for platform displacement are also present and the required sensitivity for single cell analyses is granted. The device will moreover allow the recording of the stress–strain curve for single living cells.

Micronano Structure and Mechanics Behavior of Mosquito’s Proboscis Biomaterials with Applications to Microneedle Design

The mouthparts of female mosquitoes have evolved to form a special proboscis, a natural biomicroelectromechanical system, which is used for painlessly penetrating human skin and sucking blood. The structure of the mosquito fascicle is observed using a scanning electron microscope, and the mechanical property of the labrum and maxillae, two of the most important parts of the mosquito’s fascicle is studied. The micronano structure and the special biomaterials of the mosquito’s proboscis make the mosquito penetrate easily into human skin with a surprising low force, which is measured to be only tens of micro-Newton. Our obtained results are helpful for the optimum design of the microneedles and transdermal drug delivery system.

In this issue

Abstract3D cell cultures in microfluidic systemsWitte et al., Eng. Life Sci. 2011, 11, 140–147.Culturing cells in culture flasks on solid state materials does not represent a physiological situation of a vascularized tissue. Consequently, experimental results do not always represent the in vivo situation. Therefore, authors from the TU Illmenau, Germany, report a Bio‐Micro‐Electro‐Mechanical System (BioMEMS) for the cultivation of adherent 2‐D and scaffold‐based 3‐D cell cultures in a microfluidic device. The miniaturization level and system set‐up allow incubator‐independent operation modes and long‐term experiments with real‐time microscope observation. The seeding of adherent cells into the microstructure was identified as a key issue. The modular design and set‐up offer a broad application spectrum for a variety of cell types that could for example be used for cell screening.……………140http://dx.doi.org/10.1002/elsc.201000045magnified imageAnimal disease detection on a chipSeise et al., Eng. Life Sci. 2011, 11, 148–156.The global livestock trade increases the risk of spreading animal diseases and other pathogens. Hence, new diagnostic tools that enable fast on‐site analysis are needed. These systems need to be transportable, robust and reliable and should have low power and reagent consumption. Chip‐based devices meet all of these requirements and offer the possibility of automation. In this issue, scientists from Jena, Germany, describe a DNA or RNA‐based platform for selected pathogens, such as foot‐and‐mouth disease virus (FMDV). The system incorporates a stationary PCR chip coupled with a DNA chip for electrical detection of sequence‐specific interaction of the PCR products. This technology combines the accuracy of sequence analysis with the speed of chip technologies.……………148http://dx.doi.org/10.1002/elsc.201000046magnified imageEncapsulation of Langerhans' isletsWiedemeier et al., Eng. Life Sci. 2011, 11, 165–173.Transplanting Langerhans' islets that produce insulin would be an attractive treatment of type‐1 diabetes mellitus, which is caused by an autoimmune reaction against these pancreatic cells. However, to prevent the rejection of the transplants by the immune system, a lifelong immunosuppressive medication is necessary. One possible way to prevent this rejection would be the transplantation of immunoseparated Langerhans' islets, which are encapsulated in a 3‐D‐alginate matrix, allowing for transfer of nutrients while prohibiting the infiltration of immune cells. A collaboration of researchers from academia and the clinic from Heilbad Heiligenstadt, Mainz, Saarbrücken and St. Ingbert (all Germany) demonstrate a microtechnological approach for encapsulation of cells in alginate in a reproducible and well‐controlled manner that aims at GMP compliant production and clinical use.……………165http://dx.doi.org/10.1002/elsc.201000146magnified image

Integration of 3‐D cell cultures in fluidic microsystems for biological screenings

AbstractA life support system for the cultivation of adherent 2‐D and scaffold‐based 3‐D cell cultures in a microfluidic device, a Bio‐Micro‐Electro‐Mechanical System (BioMEMS) is presented. The miniaturization level and system set‐up allow incubator‐independent operation modes and long‐term experiments with real‐time microscope observation. A dedicated seeding procedure for adherent cells into the microstructures is one key issue of the BioMEMS developed. Several seeding methods for the cells were evaluated. Biocompatibility of all materials, surfaces and methods could be demonstrated. First experiments with several cell types show the feasibility of the approach employing standard laboratory protocols. At present, the modular design and set‐up offer a broad application spectrum as well as its future extension to e.g. cultivation of other cell types, coupled cultivation chambers and the implementation of other manipulation or analysis components.

Mosquito proboscis: An elegant biomicroelectromechanical system

The mouthparts of female mosquitoes have evolved to form a special proboscis, a natural biomicroelectromechanical system (BMEMS), which is used for painlessly penetrating human skin and sucking blood. Scanning electron microscope observations show that the mosquito proboscis consists of a small bundle of long, tapering, and feeding stylets that are collectively called the fascicle, and a large scaly outer lower lip called the labium. During blood feeding, only the fascicle penetrates into the skin while the labium buckles back to remain on the surface of the skin. Here, we measured the dynamic force of penetration of the fascicle into human skin to reveal the mechanical principle underlying the painless process of penetration. High-speed video observations of movements associated with insertion of the fascicle indicate that the "smart" mosquito does not directly pierce its victim's skin with the fascicle. Instead, it uses the two maxillas as variable frequency microsaws with nanosharp teeth to advance into the skin tissue. This elegant BMEMS enables the mosquito to insert its feeding fascicle into human skin using an exceedingly small force (average of 16.5 μN).

Cold plasma functionalized TeraHertz BioMEMS for enzyme reaction analysis

In this paper, we describe the development, functionalization and functionality testing of a TeraHertz (THz) Bio-MicroElectroMechanical System (BioMEMS) dedicated to enzyme reaction analysis. The microdevice was fabricated by mixing clean room microfabrication with cold plasma deposition. The first is used to build the microfluidic circuits and the THz sensor, while the later serves for the polymerization of allylamine using a homemade glow discharge plasma reactor for a subsequent immobilization of enzymatic biocatalysts. Thermal stability of the deposited plasma polymer has been investigated by infrared spectroscopy. Fluorescent detection confirmed the efficiency of the immobilization and the enzyme hydrolysis into the BioMEMS microchannels. For the first time, the progression of the hydrolysis reaction over time was monitored by the THz sensor connected to a vectorial network analyzer. Preliminary results showed that sub-THz transmission measurements are able to discriminate different solid films, various aqueous media and exhibit specific transmission behavior for the enzyme hydrolysis reaction in the spectral range 0.06–0.11 THz.

A High-Performance Droplet Routing Algorithm for Digital Microfluidic Biochips

In this paper, we propose a high-performance droplet router for a digital microfluidic biochip (DMFB) design. Due to recent advancements in the biomicro electromechanical system and its various applications to clinical, environmental, and military operations, the design complexity and the scale of a DMFB are expected to explode in the near future, thus requiring strong support from CAD as in conventional VLSI design. Among the multiple design stages of a DMFB, droplet routing, which schedules the movement of each droplet in a time-multiplexed manner, is one of the most critical design challenges due to high complexity as well as large impacts on performance. Our algorithm first routes a droplet with higher by passibility which is less likely to block the movement of the others. When multiple droplets form a deadlock, our algorithm resolves it by backing off some droplets for concession. The final compaction step further enhances timing as well as fault tolerance by tuning each droplet movement greedily. The experimental results on hard benchmarks show that our algorithm achieves over 35 x and 20 x better routability with comparable timing and fault tolerance than the popular prioritized A* search and the state-of-the-art network-flow-based algorithm, respectively.

Nanomechanical characterization of polymer beam structures for BioMEMS applications

Polymer microstructures are incorporated in biomicroelectromechanical system (BioMEMS) devices with applications ranging from drug screening to defense applications. Nanomechanical characterization of the polymer components must be carried out in order to design reliable devices. This paper presents the nanoindentation characterization of polymer beams fabricated through soft lithography-based techniques for BioMEMS applications. Poly(propyl methacrylate) (PPMA), poly(methyl methacrylate) (PMMA), polystyrene (PS) and a nanocomposite of polystyrene and clay (PS/Clay) were investigated in this study. The hardness, elastic modulus and creep behavior of microbeams made from these materials were measured using continuous stiffness measurement (CSM) nanoindentation, and the scratch resistance of thin films was measured using a nanoscratch technique. Yield and breaking strengths were determined by normal beam bending at elevated loads, in which the presence of the nanoclay filler in the composite modified the deformation behavior relative to the unfilled polystyrene. Lateral bending of PS and PS/Clay cantilever beams is demonstrated for the first time. The mechanical response of beams after soaking in deionized water or heating to human body temperature was examined.