Development Of Microsensors Research Articles

Nanometrology based control: taming radical grafting reactions with attoliter precision.

Precisely controlled micropatterning with organic moieties is a promising route for designing smart surfaces, enabling the development of microsensors and actuators with optimal usage of reactants. Such applications require fine control over the surface modification process, which in turn demands detailed knowledge about the surface modification process. As complex surface kinetics often emerge as a result of even slight modifications of the grafting entity, non-invasive, sensitive and precise closed loop control strategies are highly desirable. In this paper we demonstrate that a nanometrology approach based on quantitative phase imaging (QPI) fulfill all these requirements. We first use the technique to monitor surface photografting kinetics of aryl radicals, comprehensively analyzing the effect of substituents on surface addition reactions. We demonstrate that several aspects of the grafting process are affected in complex ways, rendering open-loop strategies impossible to implement precisely. Then, we show that the operando optical phase signal can be used as a direct feedback, guiding the grafting reaction process. Using relatively simple instrumentation, we demonstrate that general and precise control strategies can be designed and used to control the volume of the grafting material with attoliter precision, in spite of radically different surface modification kinetics spanning several orders of magnitude.

Heterodyne detection of backscattering for whispering-gallery-mode sensors.

Whispering-gallery-mode (WGM) microcavities have shown significant applications in nanoparticle sensing for environmental monitoring and biological analysis. However, the enhancement of detection resolution often calls for active cavities or elaborate structural designs, leading to an increase of fabrication complexity and cost. Herein, heterodyne amplification is implemented in WGM microsensors based on backscattering detection mechanism. By interfering with an exotic reference laser, the reflecting light backscattered by perturbation targets can be strongly enlarged, yielding an easy-to-resolve and consequently sensitive microsensor. The dependence of detection laser frequency has also been characterized with the assistance of optothermal dynamics. We show that exploiting heterodyne interferometry boosts the detection of weak signals in microresonator systems and provides a fertile ground for optical microsensor development.

Direct Printing of Micropatterned Plasmonic Substrates of Size‐Controlled Gold Nanoparticles by Precision Photoreduction

AbstractAlthough the extraordinary optical property of gold nanoparticles (AuNPs) has been known for a long time, the anticipated applications of AuNPs in plasmonically enhanced substrates and photonic microdevices are still under development. In this paper, a method for the direct printing of micrometer‐scale patterns of size‐controlled AuNPs is presented for plasmonic substrates and microsensor development. Using in‐house digital ultraviolet lithography, a precision photoreduction technology is developed for light‐controlled growth of AuNPs to create micrometer‐scale micropatterns on a titanium dioxide photocatalytic layer. The titanium dioxide thin layer not only enables a photocatalytic reduction process for high‐precision printing of size‐controlled AuNPs in an additive manner, but also introduces a Fano resonance that can sharpen spectral width of localized surface plasmon resonance peak and increase its peak‐to‐valley value. This printing technology can be used to cost‐effectively fabricate size‐scalable micropatterned plasmonic substrates of size‐controlled AuNPs and thus offers new opportunities to develop various types of miniature plasmonic devices ranging from plasmonic biochemical sensors to plasmonically enhanced photothermal and photovoltaic microdevices.

Robust Functionalization of Large Microelectrode Arrays by Using Pulsed Potentiostatic Deposition.

Surface modification of microelectrodes is a central step in the development of microsensors and microsensor arrays. Here, we present an electrodeposition scheme based on voltage pulses. Key features of this method are uniformity in the deposited electrode coatings, flexibility in the overall deposition area, i.e., the sizes and number of the electrodes to be coated, and precise control of the surface texture. Deposition and characterization of four different materials are demonstrated, including layers of high-surface-area platinum, gold, conducting polymer poly(ethylenedioxythiophene), also known as PEDOT, and the non-conducting polymer poly(phenylenediamine), also known as PPD. The depositions were conducted using a fully integrated complementary metal-oxide-semiconductor (CMOS) chip with an array of 1024 microelectrodes. The pulsed potentiostatic deposition scheme is particularly suitable for functionalization of individual electrodes or electrode subsets of large integrated microelectrode arrays: the required deposition waveforms are readily available in an integrated system, the same deposition parameters can be used to functionalize the surface of either single electrodes or large arrays of thousands of electrodes, and the deposition method proved to be robust and reproducible for all materials tested.

(Invited) Fluorescent Frequency Domain Oxygen Sensing and Gradient Imaging within Microfluidic Structures

Development of microsensors and microfluidics have proceeded in parallel for a number of decades. The incorporation of chemical sensing within microfluidic structures presents specific challenges, however. As one of the most important electron acceptors in biology, oxygen is of particular interest as a as a factor many processes, down to the pore scale. Microfluidic structures offer unique opportunities to create microenvironments that set up gradients and environmental conditions that are relevant to biomedical or natural biogeochemical systems. Gradients of molecular oxygen are of particular interest due to the fact that many important biological processes either occur at interfaces or are regulated by the flux of oxygen and other resources. Here we describe approaches to sense oxygen concentrations and gradients within microfluidic structures, using localized films of fluorescent oxygen sensing dyes and frequency domain fluorescent lifetime imaging. Of particular interest is to design systems where the fluorescent images also match the microfluidic spatial structure within the device. This is a concern because the simplest conventional approach, sandwiching a polymer film containing an oxygen sensing dye between a cover plate and a structured base plate produces a fluorescent signal across the entire device, including (mostly) areas that have nothing to do with the microfluidic structure. By contrast, we are pursuing approaches where the fluorescent signal is only seen in microchannel areas. Diverse approaches will be contrasted for fabricating and imaging oxygen sensing microfluidic structures, including pore network structures as models for natural systems at the pore scale.

Low-cost disposable ALT electrochemical microsensors for in-vitro hepatotoxic assessment

Liver-on-chip systems are widely seen as having the potential to replace animal testing for long-term liver toxicity assessments. However, such systems necessitate solutions, such as electrochemical microsensors, to provide information about the cells exposed to chemical compounds in a confined space. This study describes the development of microsensors for the detection of alanine-aminotransferase (ALT), an intracellular enzyme found in hepatocytes, for monitoring the viability of in-vitro hepatic cell cultures. The electrochemical sensors were developed by using screen printed electrodes functionalized by drop-casting. These technologies are intended to produce disposable and low-cost sensors that can easily be exchanged once their performance is degraded. The sensors are capable of measuring ALT in a microfluidic environment through the detection of changes in glutamate concentration. The microsensors were found to be stable for more than 60 days and were successfully tested using hepatocellular lysates to assess their capability to quantify ALT activity in a hepatic cell culture. These results open the way to their integration in liver bioreactors to assess hepatocellular toxicity in-vitro.

(Invited) Nano-Derived Microsensors for Monitoring Gas Species in Harsh-Environments

The objective of our work is to develop nano-derived, micro-scale sensors to monitor various gases within extreme or harsh-environments. These environments include high temperature and pressure applications, where sensors are required to monitor emissions in applications such as coal gasifiers and turbine generators. The environment may also include applications in extreme cold and low-pressure applications, where sensors are required to monitor chemical leaks, as possible on the International Space Station and satellite servicing operations. Our research focuses on the development of microsensors for both of these extreme temperatures and pressure environments, but the current paper will only focus upon the high-temperature sensor application. In the case of the high-temperature gas sensing, nanomaterials for detecting gases such as H2 and SO2 within high-temperature environments were investigated at 1000°C. The microsensors developed in this work are based upon a resistive-type (chemiresistive) sensor platform.

Surface Enhanced Raman Scattering (SERS) Studies of Gold and Silver Nanoparticles Prepared by Laser Ablation.

Gold and silver nanoparticles (NPs) were prepared in water, acetonitrile and isopropanol by laser ablation methodologies. The average characteristic (longer) size of the NPs obtained ranged from 3 to 70 nm. 4-Aminobenzebethiol (4-ABT) was chosen as the surface enhanced Raman scattering (SERS) probe molecule to determine the optimum irradiation time and the pH of aqueous synthesis of the laser ablation-based synthesis of metallic NPs. The synthesized NPs were used to evaluate their capacity as substrates for developing more analytical applications based on SERS measurements. A highly energetic material, TNT, was used as the target compound in the SERS experiments. The Raman spectra were measured with a Raman microspectrometer. The results demonstrate that gold and silver NP substrates fabricated by the methods developed show promising results for SERS-based studies and could lead to the development of micro sensors.

A Novel Hierarchical Information Fusion Method for Three-Dimensional Upper Limb Motion Estimation

Motion capture provides the best interface to the understanding of trajectory planning and formations in the central nervous system, which has enormously benefited the research in interactive game and learning, animation, film special effects, health care, and navigation. The existing human motion capture techniques, which use structured multiple high-resolution cameras in a dedicated studio, are complicated and expensive. With the rapid development of microsensors on chip, a ubiquitous real-time low-cost human motion capture system that uses wearable microsensors becomes possible. Because of the agility in movement, upper limb motion estimation has been regarded as the most difficult problem in human motion capture. In this paper, we take the upper limb as our research subject and present a novel upper limb motion estimation algorithm by hierarchical fusion of sensor data and human skeleton constraints. Our method represents the orientations of upper limb segments in quaternion, which is computationally effective and can avoid the singularity problem. To address the nonlinear human body segment motion, a particle filter is proposed to fuse inertial and magnetic sensor data. To compensate for the drift, which is the most challenging issue in motion estimation using inertial sensors, we present a novel solution by modeling the geometrical constraint in elbow joint and fuse the constraint in the framework of particle filter to revise the sensor fusion results and improve the estimation accuracy. The experimental results have shown that the proposed algorithm can provide accurate results compared to the ground truth.

Direct Grafting of Long-Lived Luminescent Indicator Dyes to GaN Light-Emitting Diodes for Chemical Microsensor Development

Two new methods for covalent functionalization of GaN based on plasma activation of its surface are presented. Both of them allow attachment of sulfonated luminescent ruthenium(II) indicator dyes to the p- and n-type semiconductor as well as to the surface of nonencapsulated chips of GaN light-emitting diodes (blue LEDs). X-ray photoelectron spectroscopy analysis of the functionalized semiconductor confirms the formation of covalent bonds between the GaN surface and the dye. Confocal fluorescence microscopy with single-photon-timing (SPT) detection has been used for characterization of the functionalized surfaces and LED chips. While the ruthenium complex attached to p-GaN under an oxygen-free atmosphere gives significantly long mean emission lifetimes for the indicator dye (ca. 2000 ns), the n-GaN-functionalized surfaces display surprisingly low values (600 ns), suggesting the occurrence of a quenching process. A photoinduced electron injection from the dye to the semiconductor conduction band, followed by a fast back electron transfer, is proposed to be responsible for the excited ruthenium dye deactivation. This process invalidates the use of the n-GaN/dye system for sensing applications. However, for p-GaN/dye materials, the luminescence decay accelerates in the presence of O(2). The moderate sensitivity is attributed to the fact that only a monolayer of indicator dye is anchored to the semiconductor surface but serves as a demonstrator device. Moreover, the luminescence decays of the functionalized LED chip measured with excitation of either an external (laser) source or the underlying LED emission (from p-GaN/InGaN quantum wells) yield the same mean luminescence lifetime. These results pave the way for using advanced LEDs to develop integrateable optochemical microsensors for gas analysis.

Comprehensive study of an optical fiber plasmonic microsensor in a microfluidic device

In the last decade, surface plasmon resonance (SPR) has become a very sensitive technique for real-time detection of chemical and biochemical targets in many application areas. Considering the important needs for analyzing biomolecular reactions through automated and miniaturized components, optical fiber sensors based on the SPR effects are presently considered as an alternative in the development of microsensors. In the present work, a microfluidic system associated with an optical fiber SPR sensor is developed and evaluated to monitor in real-time the sensitivity of optical fiber sensor to each kinetic reaction occurring at the surface. From the kinetic parameters obtained by our experimental measurements and then implemented in the numerical model, modeling allows us to demonstrate the potential of SPR optical fiber sensors for biological analysis.

Applied breath analysis: an overview of the challenges and opportunities in developing and testing sensor technology for human health monitoring in aerospace and clinical applications

The aerospace industry requires the development of a range of chemical sensor technologies for such applications as leak detection, emission monitoring, fuel leak detection, environmental monitoring, and fire detection. A family of chemical sensors are being developed based on micromachining and microfabrication technology to fabricate microsensors with minimal size, weight, and power consumption, and the use of nanomaterials and structures to develop sensors with improved stability combined with higher sensitivity. However, individual sensors are limited in the amount of information that they can provide in environments that contain multiple chemical species. Thus, sensor arrays are being developed to address detection needs in such multi-species environments. These technologies and technical approaches have direct relevance to breath monitoring for clinical applications. This paper gives an overview of developing cutting-edge sensor technology and possible barriers to new technology implementation. This includes lessons learned from previous microsensor development, recent work in development of a breath monitoring system, and future directions in the implementation of cutting edge sensor technology. Clinical applications and the potential impact to the biomedical field of miniaturized smart gas sensor technology are discussed.

1206 金属成形金型内蔵マイクロセンサーの開発に関する研究

1206 金属成形金型内蔵マイクロセンサーの開発に関する研究

New Development of Microsensors and Microactuators

New Development of Microsensors and Microactuators

Microsensors vs. ICs: a study in contrasts

Significant differences between microsensors and micromechanisms, on the one hand, and integrated circuits, on the other, are examined from the design viewpoint. Microelectronic sensors, micromachining processes, and micromechanisms and micro-actuators are discussed. The principal technological forces driving microsensor development, namely lithography and planar technology, are considered, and some cautionary advice is given regarding the development of so-called smart sensors. Two issues in regard to the partitioning of measurement systems-device partitioning and calibration-are addressed. Technology constraints and packaging considerations are examined. >

Chemically responsive microelectrochemical devices based on platinized poly(3-methylthiophene): variation in conductivity with variation in hydrogen, oxygen, or pH in aqueous solution

Abstract : In this paper we wish to show that metal impregnated conducting polymers can be useful as the active material in microelectrochemical devices that respond to certain chemical changes in aqueous solution. We report here the impregnation of poly(3-methylthiophene) with metallic Pt in order to make the conducting polymer responsive to oxidizing and reducing species, O2 and H2, respectively, in a reversible and reproducible manner at room temperature in aqueous solution. As recently described, poly(3-methylthiophene)-based transistors can be used in aqueous solution to reproducibly respond to a redox signal, e.g. 10 to the -16 power moles of IrC16(2-) can be detected. In principle, any oxidant capable of oxidizing poly(3-methylthiophene) can be detected. However, only those redox reagents capable of equilibrating with the poly(3-methylthiophene) can be useful in turning the transistor on or off. Since the poly(3-methylthiophene)-based transistor has impressive durability to aqueous solutions, rapid response, and excellent transconductance, this chemically sensitive device is an ideal candidate for microsensor development, provided that it can be made responsive to reagents of interest. Impregnation of the polymer with a noble metal capable of equilibrating with aqueous O2 and H2 is our first step in device modification that yields potentially useful functions for the device.