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Satellite data and imagery have come a long way to improving the ability to analyze and forecast intense tropical cyclone (TC) development since the use of only visual and infrared imagery. With each new generation of sensor, knowledge of how and when a TC intensifies has expanded greatly, especially when coupled with the latest numerical models. This is especially important in the ocean basins where in situ measurements cannot be routinely obtained. A brief review of these new capabilities is presented here.

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link. Open access article Measures of fMRI brain entropy have been used to investigate age and disease related neural changes. However, it is unclear if movement in the scanner is associated with brain entropy after geometric correction for movement. As age and disease can affect motor control, quantifying and correcting for the influence of movement will avoid false findings. This work examines the influence of head motion on fMRI brain entropy. Resting-state and task-based fMRI data from 281 individuals born in Aberdeen between 1950 and 1956 were analysed. The images were realigned, followed by nuisance regression of the head motion parameters. The images were either high-pass filtered (0.008 Hz) or band-pass (0.008 Hz – 0.1 Hz) filtered in order to compare the two methods; fuzzy approximate entropy (fApEn) and fuzzy sample entropy (fSampEn) were calculated for every voxel. Motion was quantified as the mean displacement and mean rotation in three dimensions. Greater mean motion was correlated with decreased entropy for all four methods of calculating entropy. Different movement characteristics produce different patterns of associations, which appear to be artefact. However, across all motion metrics, entropy calculation methods and scan conditions, a number of regions consistently show a significant negative association: the right cerebellum crus, left precentral gyrus (primary motor cortex), the left postcentral gyrus (primary somatosensory cortex), and the opercular part of the left inferior frontal gyrus. The robustness of our findings at these locations suggests that decreased entropy in specific brain regions may be a marker for decreased motor control.

We introduce the design and fabrication of a segmented, hemispherical silicon image plane for 10 mm-diameter spherical monocentric lens. In order to conform to the spherical focal plane of the lens, we create flexible gore patterns consisting of spring-connected silicon hexagons. Mechanical functionality is demonstrated by assembling 20 µm-thick, patterned silicon gores into a curved test fixture. We have also fabricated and tested a photodiode array in a CMOS compatible process. The hemispherical imager will enable a compact 160° field-of-view camera with a fill factor over 80% using a single spherical lens.

The multiband charge-coupled device (CCD) is a polychromatic image sensor fabricated on semiconductor-on-insulator substrates with multiple device layers. It can achieve a multifold improvement in efficiency compared to a conventional CCD, because photons are collected and resolved in the substrate without external optics. We present the first experimental demonstration of multiband light absorption and charge extraction for a single-pixel device. The ratio of the active layers' responsivities changes with wavelength, indicating that incident color information is captured in the multiple device layers.

A large dc bias voltage (tens of volts) is often useful for the operation of capacitive MEMS devices. Charge-biasing techniques have been demonstrated to be able to replace a bias voltage source by trapping an equivalent charge on an electrically floating electrode. This work presents a charge-biased resonator that uses an electrostatically actuated mechanical switch with a pull-in voltage of 36 V to introduce a voltage-equivalent charge of 10-15V onto a resonant body. The switch and resonator are hermetically sealed in a clean vacuum cavity, within an epitaxial polysilicon encapsulation process (epi-seal). No charge leakage has been observed, even at an elevated temperature of 125°C for weeks.

In this manuscript we present a three-component sample preparation platform for delivering proteins, with controlled orientation, purified from a complex biological sample to a sensor surface. The presented platform depletes highly abundant proteins and cells from complex biological samples, and then is capable of immobilizing the target analyte on the surface with controlled immobilization. A herringbone structure is used to mix the test sample with beads coated with antibodies against the highly abundant proteins, which is then fed into a second component, consisting of a filter trench with interdigitated electrodes above for applying dielectrophoretic force. The beads and cells are pushed down into the filter trench, thus allowing only the serum to pass through. In a third step, protein orientation and immobilization is controlled with electric field. In this manuscript we discuss the proof of concept for each of these three components separately.

By increasing the strength of the negative dielectrophoresis (DEP) force, we demonstrate a significantly improved electrokinetic actuation and filtering microsystem. A pinhole-free, nanometer-scale, thin film oxide was deposited using atomic layer deposition, as a protective layer to protect the electrodes from corrosion, when applying high AC voltages (>20 Vpp) at the electrodes. The electrodes were capacitively coupled to the electrolyte buffer by the application of a high frequency AC voltage signal, thus avoiding electric field degradation and the consequent reduction in dielectrophoresis force due to the presence of the insulating oxide layer. In this work, we demonstrated the use of this DEP-enhanced device for two microfluidic applications. First, we demonstrate an on-chip platform for the depletion of cells and highly abundant serum proteins in blood, which is a prerequisite to assay low-abundance protein biomarkers. For the second application, we show 100% detachment of anti-IgG and IgG bound beads (which is on the same order of magnitude in strength as typical antibody-antigen interactions) from the surface, upon the application of the enhanced negative DEP force. This capability offers the possibility of performing a bead-based multiplexed assay against multiple antigen targets where in a single microfluidic channel various regions are immobilized with a different antibody, each targeting a different antigen.

A novel design for a six-terminal nanoelectromechanical relay is presented. The design includes a secondary beam in the signal pathway of the device, which allows direct contact between the source and drain. The advantages of the new design include avoidance of fabrication-based contact degradation during the isolation etch, lower sensitivity to high gap variations and reduction in the number of contacts needed to close the signal pathway. Also, the new design introduces a novel anti-stiction mechanism. An analytical model is presented which compares the mechanical behavior of the new design to the older design. The devices are fabricated using a silicon nitride hard mask with an ammonium hydroxide based etchant. An inverter made using the new design is demonstrated.

We report on the modeling, fabrication and characterization of a new serpentine geometry for platinum bolometers realized with plasma-enhanced atomic layer deposition (PEALD). The measured responsivity of 7.5 · 107 VW-1 A-1 of the proposed structure is almost four times higher than that of previously published PEALD deposited platinum bolometers with a traditional square absorber design [1]. This improvement was achieved without increasing the sensor's footprint or fabrication complexity.

We evaluated the chemical and electrochemical corrosion resistance of ultra-thin films deposited via atomic layer deposition (ALD) for potential wafer-scale passivation of biomedical microdevices. A variety of ALD coatings can be deposited conformally on metal or silicon surfaces at low temperature. We were able to protect aluminum electrodes against corrosion in ionic media with a voltage stress of 1V for 200 hours using a double ALD film stack of 5nm Al2O3 and 5nm HfO2.

We present a rapid prototyping substitute for silicon MEMS Fabrication, which allows students to understand the fundamental tradeoffs in designing a planar accelerometer. The laboratory uses commercially available polymer-films and a CO2 laser cutter for device fabrication and design validation.

Laterally actuated nanoelectromechanical relays with compliant source-drain contacts are presented. The relay sidewalls are coated with a 30 nm-thick conductive layer of titanium nitride (TiN) deposited using atomic layer deposition (ALD). By hollowing the tip of the relay, a flexible sidewall is formed from the thin TiN that results in a larger contact area and therefore improves the contact properties of the relay. This modification improves the on-state resistance (RON) and also provides better stability over a larger number of switching cycles compared to a rigid contact. The results of life-time tests show that the contact resistance increases with the number of switching cycles possibly due to degradation of the contact material. However, flexible contacts show improved contact resistance stability under cyclic contact.

We report the realization of coalescent free-standing ultra-thin (as thin as 5.5 nm) platinum layers deposited via plasma-enhanced atomic layer deposition and their characterization as an uncooled infrared detector. Such thin platinum thermistors enable a responsivity as high as 2 · 107 V/WA, an estimated noise equivalent temperature difference of 163 mK and thermal time constants on the order of 1 ms.

CuPc-based organic thin-film transistor (OTFT) with high-k dielectric HfAlO as gate dielectric prepared by atomic layer deposition has been fabricated. Experimental results show that the HfAlO-OTFT has higher mobility, smaller sub-threshold slope and larger on/off ratio than the HfO 2 sample. All these should be attributed to the addition of Al into the HfO 2 film confirmed by X-ray photoelectron spectroscopy, resulting in improved dielectric and interfacial properties. Moreover, the reliablity of the device upon exposure to air is investigated.

We present the multiband charge-coupled device (CCD), a new CCD architecture that contains multiple vertically stacked active layers, capable of generating color images without the use of external filters. One of the applications is to embed the band-resolving capability of astronomical cameras into the CCD and therefore improve the overall survey speed of the telescope. As a proof of concept, we describe a three-layer, three-phase, front-illuminated prototype and simulate its multiband absorption and charge-detection performance.

We describe the fabrication of a double-layer silicon photonic crystal using self-aligned CMOS-compatible processes and its assembly on a single mode fiber using a wafer template and epoxy bonding. The fiber sensor has sharper resonances and higher temperature sensitivity than the previously-reported single-layer sensor. The new assembly method facilitates batch-production of the sensor and allows for extension to high temperature measurement.

Nano-Electro-Mechanical (NEM) relays are nano-scale switches that can be mechanically actuated by an electrical signal. Unlike conventional CMOS transistors, NEM relays exhibit zero off-state leakage and very sharp on-off transitions. As a result, NEM relays can be potentially used to design highly energy-efficient digital systems. NEM relays are also excellent candidates for programmable routing switches in Field Programmable Gate Arrays (FPGAs) due to their potentially low on-state resistances despite their long mechanical delays. Low-temperature fabrication of NEM relays creates opportunities for their integration on top of silicon CMOS circuits. Hysteresis properties of NEM relays can enable their use as FPGA programmable routing switches without requiring additional routing SRAM cells. In this talk, we will present an overview of NEM relays and their use in digital system design, and discuss design considerations for hybrid CMOS-NEM FPGAs.

This paper reports an initial prototype for microfabricated silicon carbide (SiC) thermionic energy converters (TECs), which have promise as topping stages for solar thermal electricity generation. Our initial TEC device achieved cathode temperatures of over 2000 K with incident optical intensity of approximately 1 W/mm2 (equivalent to 1000 Suns), remained structurally stable under thermal cycling, and maintained a temperature difference between the cathode and the anode of over 1000 K. In addition, our device converted the estimated 0.1 W of optical power incident on the cathode to 0.12 nW of electrical power. The low conversion efficiency is due to the high work function of SiC, which severely limits the thermionic current. According to the Richardson-Dushman equation, the thermionic current should increase by more than six orders of magnitude if we cesiate both electrodes of the converter, increasing the efficiency accordingly. In our initial experiments, the thermionic current was enhanced by ∼1.5 orders of magnitude using the cesium coating.

We investigate DNA passage through a nanofluidic transistor (NFT) composed of large diameter nanopores (~200nm) with an embedded metal gate. The nanopores are large enough to be made by currently available photolithography process for manufacturability. We observe that the NFT is capable of electrostatic control of DNA capture rate, the equivalent of current in the electron transistor, with similar operating principle as their electron device counterpart.

This paper demonstrates electrical results of an integrated Si CMOS-electrostatically actuated nanoelectromechanical (NEM) relay circuit. This is an initial step towards realizing previously proposed NEM-CMOS hybrid circuits that predict various benefits compared to CMOS-only circuits. In this work, an e-beam patterned laterally actuated Pt NEM relay is fabricated at CMOS-compatible temperatures (≤ 400 °C) on top of CMOS and is driven by an on-chip CMOS inverter at V DD = 6 V.

Most underwater images are post-processed to look pleasing to human viewers. This often results in unrealistically saturated colors. Images taken for the purpose of studying color-sensitive topics such as marine animal coloration, must represent colors as accurately as possible and should not be arbitrarily enhanced. This first requires a transformation of colors from the camera color space to a device independent space. In this paper we present a method for transforming raw camera-RGB colors to a device independent space, optimizing this transformation for a particular underwater habitat. We have conducted an extensive study of the variation of color appearance underwater at a dive site in the Aegean Sea by taking 21 sets of spectrometry and irradiance readings with corresponding photographs of four different color standards. Spectral and photographic data were collected in the presence of natural daylight at various depths and under different weather conditions. In addition to the color charts, we have built a “habitat chart” to optimize this camera-specific transformation for a given dive site.

NEM relay is a promising class of device to overcome the power crisis of CMOS circuits. To design these devices and predict their scaling properties, an analytical model highlighting the fundamental physics of the relay operation is highly desired. This work presents a new 2D analytical model for the study of NEM relay scaling. The model retains the physical insights for NEM relays and yet has the simplicity close to the commonly used 1D model. The error as compared to a finite element model is reduced from ∼25% (1D model) to ∼3% (this work) by introducing a ratio R(a) to account for 2D effects in the 1D formulation. Besides the fundamental mechanical and electrical properties, the model also takes into account surface forces in the operation of NEM relay devices. The impact of surface forces on the operation voltage as devices are scaled down is discussed.

We describe a double-layer monolithic silicon photonic crystal (PC) fiber tip sensor. The PC is fabricated using wafer-scale Si processing and epoxy bonding to the fiber. The sensor has sharper resonances and higher sensitivity to refractive index than previously-reported single-layer PC fiber tip sensors. The bonding technique enables batch production.

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link We investigated the association between individual differences in cognitive performance in old age and the approximate entropy (ApEn) measured from functional magnetic resonance imaging (fMRI) data acquired from 40 participants of the Aberdeen Birth Cohort 1936 (ABC1936), while undergoing a visual information processing task: inspection time (IT). Participants took a version of the Moray House Test (MHT) No. 12 at age 11, a valid measure of childhood intelligence. The same individuals completed a test of non-verbal reasoning (Raven’s Standard Progressive Matrices [RPM]) aged about 68 years. The IT, MHT and RPM scores were used as indicators of cognitive performance. Our results show that higher regional signal entropy is associated with better cognitive performance. This finding was independent of ability in childhood but not independent of current cognitive ability. ApEn is used for the first time to identify a potential source of individual differences in cognitive ability using fMRI data.

A general mathematical model of viral infections inside a spherical organ is presented. Transported quantities are used to represent external cells or viral particles that penetrate the organ surface to either promote or combat the infection. A diffusion mechanism is considered for the migration of transported quantities to the inner tissue of the organ. Cases that include the generation of latent infected cells and the delivery of anti-viral treatment are analyzed. Different anti-viral mechanisms are modeled in the context of spatial variation. Equilibrium conditions are also calculated to determine the radial profile after the infection progresses and therapy is delivered for a long period of time. The dynamic and equilibrium solutions obtained in this paper provide insight into the temporal and spatial evolution of viral infection for optimal therapies.

Microfabricated thermionic emitters form a crucial part of thermionic energy converters, which could find applications in future concentrated solar thermal power plants. Here we report a new stress-relieved design for p-doped and n-doped silicon carbide (SiC) emitters, measurements of their thermionic emission and work functions at temperatures of up to 2900K, and the effect of optical irradiation on both types of SiC emitters. We also report the first observation of the photon-enhanced thermionic emission (PETE) in a thin-film microfabricated emitter.

Silicon gyroscopes and resonators have motivated rapid progress in techniques for wafer-level, high-quality vacuum encapsulation. This paper reviews recent developments in this technology and describes how it provides a foundation for new microsystem applications that involve electron transport across vacuum gaps. Thermionic energy converters, as well as the recently reported photon-enhanced thermionic energy converter, involve vacuum encapsulation of microcathode arrays. These devices pose a variety of material and process challenges, due to their high operating temperatures. A second promising application is aimed at efficient generation and processing of signals in the THz region, by means of resonant-cavity vacuum oscillators.

Laterally actuated nanoelectromechanical (NEM) relays are implemented using a polysilicon structural layer with hafnium oxide (HfO 2 ) and platinum dual sidewall layers. Atomic layer deposition (ALD) HfO 2 provides electrical isolation between the polysilicon beam structure and the sputtered platinum conductive channel. Dual sidewall devices are demonstrated using a Y-shaped device with two contacts that connect source and drain upon actuation. Fabricated devices show up to 1µA current passing between source and drain without beam current flow, confirming successful isolation.

This paper describes the fabrication and testing of a one-axis polymer-based capacitive accelerometer made using a reel-to-reel/roll-to-roll compatible, printing-based process. The accelerometer is a suspended parallel-plate sense capacitor made from a laser-printed polystyrene composite material on a flexible plastic substrate. With a simple analog voltage readout circuit, device sensitivity is 58mV/g with +/−1.5g range. This device demonstrates fabrication of ultra-low-cost MEMS sensors on flexible polymer substrates.

This paper presents low-voltage, high-aspect-ratio scaled lateral electrostatic actuators based on a four-mask multi-spacer process. The set of TEOS spacers, polysilicon hardmask, and buffer LTO layer is chosen as masking materials, resulting in a multi-spacer of LTO-TEOS and a stack of LTO-polysilicon hardmask. These mask sets with a photoresist mask are then transferred to an underlying polysilicon layer, creating high-aspect-ratio (>5∶1) polysilicon structures with sublithographic beam width and gap size. Two types of scaled actuators have been successfully designed and actuated with more than an order of magnitude reduction in actuation voltage compared to the regular process: coupled and decoupled designs of springs and movable electrodes.

The surfaces of a microfabricated polysilicon test structure, designed to measure adhesion forces in MEMS, were modified with a thin (∼50 nm) silicon carbide coating to take advantage of the outstanding tribological, electrical, and chemical properties of polycrystalline SiC (polySiC). Adhesion forces in polySiC-coated interfaces as a function of apparent area of contact have been determined quantitatively and compared to those in uncoated polycrystalline silicon (polySi) contacts. A detailed study of changes in physico-chemical surface properties after >100 billion contact cycles is also presented, highlighting suppression of wear upon SiC coating.

This work demonstrates the application of pulsed-laser processing for sealing release holes in silicon membranes. Holes in the membrane are sealed without deposition, similar to the silicon surface migration sealing process. In contrast to the 1100°C furnace anneal required for the migration process, the pulsed-laser process localizes the heat to the top few microns of the substrate, with the bulk kept at near to room temperature. In addition, there is no need for special surface treatment, or for a controlled environment. Furthermore, the treatment can be applied to selected regions of the substrate.

This paper reports on the modeling, fabrication, and testing of cantilever- and parallel plate-based laterally actuated platinum-coated polysilicon nanoelectromechanical (NEM) relays. The polysilicon acts as the structural layer, while the platinum serves as a conducting contact material, as well as a local routing layer. The two-part cantilever design utilizes a source made of a compliant beam in series with a stiff bridged perimeter electrode to reduce the secondary pull-in of the source to the gate. The parallel-plate-based relay also uses stiffened electrodes in addition to serpentine structures that reduce the actuation voltage. Overdrive gate voltage in excess of 100% without failure and sharp release of the relay from output are achieved for polysilicon relays with 50nm platinum coating and 500nm actuation gap.

This paper presents an uncooled infrared bolometer using a metal thin film that is formed by atomic layer deposition (ALD). Nanometer-thick freestanding layers enabled by ALD have the potential to improve the performance of bolometers with achieving low thermal conductance and near optimal optical properties. The fabrication and characterization of the first implementation are described as well as the electrical properties of ALD platinum films.

We demonstrate a pH sensor utilizing a layout-programmed squeeze-pumped microfluidic platform. The device is fabricated via direct polydimethylsiloxane (PDMS) micromilling and utilizes an external single-actuator squeeze pump for simultaneous pumping of multiple fluids at different layout-determined flow volumes from 300–9000pL/step. The pumping system, akin to the development of Polaroid instant film, provides an inexpensive means for operating disposable microfluidic devices in the field without external power supplies, valves, or fluidic interface ports. The pH sensor demonstrates functionality of this low-cost, disposable, lab-on-a chip microfluidic detection system.

This paper considers the electromechanical response of electrostatic actuators that are driven by both voltage and charge. The model system is an electrostatic actuator in which the suspended electrode is subjected to a driving voltage and the fixed electrode, which is electrostatically floating, is loaded by charge. The response of the system is analyzed using energy methods, and it is shown that the system has two distinct pull-in voltages. It is also shown that the amplitude of charge on the floating electrode is proportional to the average of these two pull-in voltages. Test-actuators were designed, fabricated, and characterized, and their measured response validates the theoretical predictions. A nondisruptive measurement of charge is proposed and demonstrated which enables to monitor charge decay over time.

This paper presents a four-mask fabrication process of lateral nanoelectromechanical (NEM) electrostatic actuators based on spacer technology. Critical dimensions of the actuators, i.e., the beam width and the gap size between the movable and fixed electrodes can be made smaller than the lithographic resolution by creating nitride spacers on an oxide hardmask followed by selective etching of the oxide hardmask. The combined oxide hardmask, nitride spacer, and another mask (photoresist mask) is then transferred to an underlying polysilicon structural layer to create lateral NEM electrostatic actuators with narrow beam and narrow gap.

This paper reports internal dielectric transduction of the 41st radial bulk-mode of a ring resonator at 2.79GHz with a quality factor exceeding 11,500 in air. The transducer electrodes are integrated within the vibrating structure in a dense serpentine pattern, with the dielectric-filled gaps strategically placed on the nodal lines to excite the 41st order bulk radial mode. The serpentine dielectric transduction results in a low motional resistance of less than 500Ω, which can be detected by direct two-port transmission measurements. The “notched” ring design allows for anchoring this resonator at the center nodal line of the ring, resulting in higher Q and lower motional resistance. This resonator is fabricated by a double nanogap process, where 30nm silicon nitride sidewall layers are formed using a combination of optically defined trenches and deposition of a high-к dielectric followed by a doped polysilicon layer.

This paper reports on lateral nanoelectromechanical (NEM) relays based on variations of a two- or three-mask titanium nitride (TiN) sidewall stringer process. Electrically isolated TiN perimeter beams are fabricated from stringers formed on the inside walls of polysilicon trenches, yielding 200nm wide TiN fins and 200nm gaps; these dimensions are 3X smaller than the resolution limit of the optical lithography tool (600nm) utilized. The reduction in the operating voltage is about a factor of 5 compared to 600nm wide polysilicon beams. Simple scaling could potentially enable sub-1V operation. Five-terminal NEM relays demonstrate successful switching in both directions over 1000 DC-sweep cycles with low drain bias (100mV).

This paper reports internal electrostatic transduction of the 41st radial bulk-mode of a ring resonator at 2.75GHz with a quality factor of 7200 in air. The transducer electrodes are integrated within the vibrating structure in a dense serpentine pattern and strategically placed on the nodal lines to excite the 41st order bulk radial mode. The serpentine dielectric transduction results in a low motional resistance of 475Ω detected by direct two-port measurements. This resonator is fabricated by a double nanogap process, where 30nm Si 3 N 4 sidewall layers are formed using a combination of optically defined trenches and deposition of a high-к dielectric followed by a doped polysilicon layer.

We present a biasing technique and a novel oscillator architecture for the elimination of frequency drifts in resonant electrostatic MEMS that are caused by the motion of charge present within dielectrics. We demonstrate more than two orders of magnitude improvement in stability for a test device operating as a frequency reference at 1.077 MHz, reducing frequency drift from more than 100 Hz over 3 hours using traditional actuation, down to less than 1.5 Hz variation over 40 hours using the new technique.

We demonstrate that monolithic 2-dimensional photonic crystals (PCs) confined to the facet, or tip, of single-mode optical fibers can be designed as highly sensitive temperature sensors. Monolithic 2-D photonic-crystals are fabricated on silicon wafers and subsequently released and micro-assembled onto the tip of optical fibers. The PC's reflection spectrum is modulated by the temperature of the sensor and its environment and shows sensitivity comparable to Fiber Bragg Gratings (FBGs). In contrast to FBGs, the compact sensing element is localized at the tip of the fiber and the active sensor element is a disk of 10µm diameter and 480 nm thickness. The sensor system is made of robust, high-temperature dielectric materials and therefore has the potential to be used for many applications including measurements in harsh environments.