Plasmomechanical Systems: Principles and Applications

AbstractExtreme confinement of electromagnetic waves and mechanical displacement fields to nanometer dimensions through plasmonic nanostructures offers unprecedented opportunities for greatly enhanced interaction strength, increased bandwidth, lower power consumption, chip‐scale fabrication, and efficient actuation of mechanical systems at the nanoscale. Conversely, coupling mechanical oscillators to plasmonic nanostructures introduces mechanical degrees of freedom to otherwise static plasmonic structures thus giving rise to the generation of extremely large resonance shifts even for minor position changes. This nanoscale marriage of plasmonics and mechanics has led to the emergence of a new field of study called plasmomechanics that explores the fundamental principles underneath the coupling between light and plasmomechanical nanoresonators. In this review, both the fundamental concepts and applications of plasmomechanics as an emerging field of study are discussed. After an overview of the basic principles of plasmomechanics, the active tuning mechanisms of plasmonic nano‐mechanical systems are extensively analyzed. Moreover, the recent developments on the practical implications of plasmomechanic systems for such applications as biosensing and infrared detection are highlighted. Finally, an outlook on the implications of the plasmomechanical nanosystems for development of point‐of‐care diagnostic devices that can help early and rapid detection of fatal diseases are forwarded

Sensitive thermal transitions of nanoscale polymer samples using the bimetallic effect: Application to ultra-thin polythiophene

A sensitive nanocalorimetric technology based on microcantilever sensors is presented. The tech- nology, which combines very short response times with very small sample consumption, uses the bimetallic effect to detect thermal transitions. Specifically, abrupt variations in the Young’s modu- lus and the thermal expansion coefficient produced by temperature changes have been employed to detect thermodynamic transitions. The technology has been used to determine the glass transition of poly(3-thiophene methyl acetate), a soluble semiconducting polymer with different nanotechno- logical applications. The glass transition temperature determined using microcantilevers coated with ultra-thin films of mass = 10 − 13 gis5.2 ◦ C higher than that obtained using a conventional differential scanning calorimeter for bulk powder samples of mass = 5 × 10 − 3 g. Atomistic molecular dynamics simulations on models that represent the bulk powder and the ultra-thin films have been carried out to provide understanding and rationalization of this feature. Simulations indicate that the film-air in- terface plays a crucial role in films with very small thickness, affecting both the organization of the molecular chains and the response of the molecules against the temperature.Peer ReviewedPostprint (published version

Monitoring CO Concentration in Fuel Cells Using Microcantilever Sensors

Estimating the concentration of gases including carbon monoxide (CO) in the hydrogen fuel exiting the reformer and entering the fuel cell is imperative. A high concentration of CO can cause fuel-cell catalyst poisoning, which permanently destroys the cell. Current practices call for utilizing expensive and bulky spectral analyzers to achieve this task. In addition to their high cost, these methodologies, undoubtedly, hinder the portability and self-containment of the cell. To overcome these problems and achieve the desired objectives of a portable, self-contained, and real-time measurement module, this thesis presents and experimentally investigates a new enabling technology based on utilizing an array of microcantilever sensors to detect minute concentrations of CO in the fuel cell. Results of this study indicate that microcantilevers can be spin coated with homogenous layers of copper-exchanged Y zeolite (CuY). This zeolite is capable of adsorbing CO over a range pressures and fuel cell operating temperatures. As a result of this adsorption, the sensor experiences a shift in its resonance frequency, which can be measured and related to the concentration of CO. It is determined that maximum adsorption capacity of the sensor occurs at 40 oC using CuY zeolite that is loaded with 10 wt% Cu. Furthermore, experimental findings indicate that the sensitivity of the sensor increases as the number of zeolite layers is increased up to a certain threshold (4 layers). Beyond this threshold, adding more layers will only result in a less sensitive sensor. In the experiments described in this thesis, a maximum repeatable shift of 275 Hz in the first modal frequency of the microcantilevers is measured. Ultimately, such frequency shifts can be iii related to the concentration of CO in the gas mixture, allowing closed-loop, real-time control and diagnosis of the flow of gases into and out of the fuel cell. This can help avoid fuel-cell starvation and prevent catastrophic deactivation of the necessary fuel cell catalyst

Novel Cantilever Sensor for Antibody-based and hlyA gene-based Sensitive Detection of Foodborne Pathogen: Listeria monocytogenes

The objectives of this research can be broadly categorized as: 1) Cantilever sensor design and characteristics, 2) Improved surface chemistry for immobilization of recognition molecules and 3) Sensing of contaminants in food and cell-culture matrix.A novel asymmetrically anchored piezoelectric millimeter-sized cantilever (aPEMC) design was developed. The new cantilever design is simpler and has lesser fabrication variables that improved the reproducibility of these devices. The sensor design was corroborated and characterized using finite element modeling and these were shown to be highly sensitive (~1 fg/Hz) via molecular chemisorption studies. The importance of the binding strength between the sensor and the added mass was shown to govern the type of resonance frequency change exhibited by the cantilever sensors and the high-order resonance oscillation modes were characterized by comparing responses to that quartz crystal microbalance (QCM) and finite element modeling.A novel and dry method for grafting reactive amine groups on polyurethane surfaces using pulsed-plasma generation of ammonia gas was demonstrated. Grafting of amine groups was corroborated by FTIR studies and SEM micrographs in addition to the cantilever sensor responses to protein immobilization. A method using tris(2-carboxyethyl)phosphine (TCEP) to reduce the disulfide bridges in antibody molecules, without affecting the antigen binding activity, to expose their native thiol groups for immobilization of gold surfaces was developed. The half antibody fragments were shown to improve the detection sensitivity of QCM biosensors without loss of selectivity.Piezoelectric millimeter-sized cantilever (PEMC) sensors were used to demonstrate detection of cell-culture mycoplasmas in buffer and cell-culture matrix at 103 CFU/mL. The detection responses were confirmed by using a second antibody binding step, much like ELISA sandwich format. aPEMC sensors were used to show detection of foodborne pathogen, Listeria monocytogenes (LM), in buffer and milk at concentration of 103/mL. The detection sensitivity was limited by commercially available low-avidity antibody. The single copy, virulence hlyA gene of LM was used to design a DNA probe that was used to detect genomic DNA extracted from LM in the presence of ~104 times higher non-target genomic DNA. Detection of genomic DNA equivalent to 7×102 LM was achieved within ~90 min.Ph.D., Chemical Engineering -- Drexel University, 201

MICROMANIPULATOR-RESONATOR SYSTEM FOR SELECTIVE WEIGHING OF INDIVIDUAL MICROPARTICLES

Over the past decade, MEMS-based cantilever sensors have been widely used in the detection of biomolecules, environmental pollutants, chemicals and pathogens. Cantilever-based sensors rely on attachment of target entities on their surface. The attachment causes either change in surface stress or resonance frequency of the cantilever, which is detected using various schemes that range from optical to piezoelectric. The majority of these sensors rely on probabilistic attachment of multiple target entities to the sensor surface. This introduces uncertainties since the location of the adsorbed target entity can modify the signal generated by the sensor. In addition, it does not allow the measurement of individually selected target entities. The goal of this dissertation is to exploit the cantilever-based sensors\u27 mass sensing capability to develop a supermarket weight scale for the micro world: a scheme that can enable the user to pick an individual target entity and weigh only that particular entity by precisely positioning it on a micro- weight scale

Gradient Field Transduction of Nanomechanical Resonators

Das Forschungsgebiet nanomechanischer Systeme betrachtet die Bewegung von Strukturen, deren Länge in mindestens einer Richtung deutlich unter einem Mikrometer liegt. Meist werden dabei Auslenkungen untersucht, die in der Nähe einer mechanischen Resonanz angetrieben werden. Das wissenschaftliche Interesse an solchen Strukturen hat mehrere Gründe: aufgrund der kleinen Masse und oftmals geringen Dämpfung (d.h. hohe Güte) reagieren solche nanomechanischen Systeme sehr empfindlich auf Änderungen ihrer Umgebung oder ihrer eigenen Eigenschaften wie etwa ihrer Masse. Die große Vielfalt der nanomechanischen Systeme erlaubt die Kopplung an verschiedenste physikalische Größen wie (Umgebungs-)Druck, Licht, elektrische/magnitische Felder. Dies ermöglicht, die Wechselwirkung selbst zu untersuchen oder entsprechende Änderungen empfindlich zu detektieren. Im Rahmen der vorliegenden Arbeit wurde die Resonator Bewegung von doppelseitig eingespannten Balken untersucht; diese wurden mit konventioneller Mikrofabrikation aus verspanntem Silizium-Nitrid gefertigt. Die große Zugspannung in den Balken führt zu einer hohen mechanischen Stabilität und ebenso zu hohen mechanischen Güten. Ein Teil der Arbeit befasste sich mit der Entwicklung neuer Detektions- und Antriebsmechanismen. Unter Ausnutzung der Polarisierbarkeit des Resonators wurde ein lokaler Antrieb realisiert, der sich durch besondere Einfachkeit auszeichnet. Ebenso wurden Fortschritte in der optischen Detektion erzielt. Ein Photodetektor konnte innerhalb einer optischen Wellenlänge Abstand zum Resonator plaziert werden; dies ermöglicht die lokale Detektion seiner Bewegung. Hochempfindliche Messungen nutzen oft optische Resonanzen; bisherige Umsetzungen basieren auf Reflexionen und sind daher auf Objekte beschränkt, die größer als die verwendete Wellenlänge sind. In einer Zusammenarbeit mit Prof. Kippenberge konnte diese Beschränkung umgangen werden, indem geführtes Licht in einem Mikro-Toroiden verwendet wurde. Weiter wurde in der Arbeit die resonante Bewegung selbst untersucht. Im Bereich hoher Amplituden zeigt die rücktreibende Kraft nichtlineares Verhalten. Das sich dadurch ergebende bistabile Verhalten des Resonators wurde mit Hilfe von kurzen, resonanten Pulsen untersucht; schnelles Schalten wurde erreicht. Die mechanische Dämpfung der Siliziumnitrid Resonatoren wurde untersucht. Die hohen Güten von Systemen unter Zugspannung konnte erklärt werden durch die sich ergebende erhöhte gespeicherte elastische Energie; im Gegensatz zu einem veränderten Dämpfungsverhalten

Nanomechanical motion transducers for miniaturized mechanical systems

Reliable operation of a miniaturized mechanical system requires that nanomechanical motion be transduced into electrical signals (and vice versa) with high fidelity and in a robust manner. Progress in transducer technologies is expected to impact numerous emerging and future applications of micro- and, especially, nanoelectromechanical systems (MEMS and NEMS); furthermore, high-precision measurements of nanomechanical motion are broadly used to study fundamental phenomena in physics and biology. Therefore, development of nanomechanical motion transducers with high sensitivity and bandwidth has been a central research thrust in the fields of MEMS and NEMS. Here, we will review recent progress in this rapidly-advancing area. © 2017 by the authors

Doctor of Philosophy

dissertationFor the past two decades, tip-based thermal engineering has made remarkable advances to realize unprecedented nanoscale thermal applications, such as thermomechanical data storage, thermophysical/chemical property characterization of materials in nanomet

Doctor of Philosophy

dissertationFor the past two decades, tip-based thermal engineering has made remarkable advances to realize unprecedented nanoscale thermal applications, such as thermomechanical data storage, thermophysical/chemical property characterization of materials in nanometer scale, and scanning thermal imaging and analysis. All these applications involve localized heating with elevated temperature, generally in the order of mean free paths of heat carriers, thus necessitates fundamental understanding of sub-continuum thermal transport across point constrictions and within thin films. Considering the demands, this dissertation is divided into three main scopes providing: (1) a numerical model that provides insight onto nanoscale thermal transport, (2) an electrothermal characterization of a heated microcantilever as a localized heating source, and (3) qualitative measurement of tip-substrate thermal transport using high resolution nanothermometer/heater. This dissertation starts with a literature review on the three aforementioned scopes followed by a numerical model for two-dimensional transient ballistic-diffusive heat transfer combining finite element analysis with discrete ordinate method (DOM-FEA), seeking to provide insight on subcontinuum thermal transport. The phonon Boltzmann transport equation (BTE) under grey relaxation time approximation is solved for different Knudsen numbers. Next, a thermal microcantilever, as one of the main tools in tip-based thermal engineering, is characterized under periodic heating operation in air and vacuum using 3ï·ï€ technique. A three-dimensional FEA simulation of a thermal microcantilever is used to model heat transfer in frequency domain resulting in good agreement with the experiment. Next, quantitative thermal transport is measured by a home-built nanothermometer fabricated using combination of electron-beam lithography and photolithography. An atomic force microscope (AFM) cantilever is used to scan over the sensing probe of the nanothermometer at an elevated temperature causing local cooling. The experiment is done in air resulting in a tip-substrate effective thermal conductance of 32.5 nW/K followed by theoretical calculations predicting contribution of solid-solid thermal conduction to be 48%. Finally, the same experiment is conducted in vacuum with similar operating condition, showing 50% contribution of solid-solid conductance, which is in good agreement with the theory, assuming no water meniscus in vacuum condition. The outcomes of these studies provide a strong platform to fundamentally understand thermal transport at the micro/nanometer scale