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https://www.readbyqxmd.com/read/29651523/simple-and-inexpensive-micromachined-aluminum-microfluidic-devices-for-acoustic-focusing-of-particles-and-cells
#1
Gayatri P Gautam, Tobias Burger, Andrew Wilcox, Michael J Cumbo, Steven W Graves, Menake E Piyasena
We introduce a new method to construct microfluidic devices especially useful for bulk acoustic wave (BAW)-based manipulation of cells and microparticles. To obtain efficient acoustic focusing, BAW devices require materials that have high acoustic impedance mismatch relative to the medium in which the cells/microparticles are suspended and materials with a high-quality factor. To date, silicon and glass have been the materials of choice for BAW-based acoustofluidic channel fabrication. Silicon- and glass-based fabrication is typically performed in clean room facilities, generates hazardous waste, and can take several hours to complete the microfabrication...
April 12, 2018: Analytical and Bioanalytical Chemistry
https://www.readbyqxmd.com/read/29627889/nonenzymatic-determination-of-glucose-at-near-neutral-ph-values-based-on-the-use-of-nafion-and-platinum-black-coated-microneedle-electrode-array
#2
Somasekhar R Chinnadayyala, Ilhwan Park, Sungbo Cho
The authors report on a microneedle-based amperometric nonenzymatic glucose sensor for painless and continuous monitoring of glucose. It consists of 3 × 5 sharp stainless steel microneedles micromachined from a stainless steel substrate. The microneedles are 600 and 100 μm in height and width, respectively. Nafion and platinum black were sequentially coated onto the tip of gold-coated microneedles and used for nonenzymatic (direct) sensing of glucose. Attractive features of the modified microneedle electrode include (a) a low working potential (+0...
April 7, 2018: Mikrochimica Acta
https://www.readbyqxmd.com/read/29617566/simultaneous-printing-of-two-inks-by-contact-lithography
#3
David Moore, Ravi F Saraf
Microcontact printing (µCP) is a valuable technique used to fabricate complex patterns on surfaces for applications such as sensors, cell seeding, self-assembled monolayers of proteins and nanoparticles, and micromachining. The process is very precise but is typically confined to depositing a single type of ink per print, which limits the complexity of using multifunctionality patterns. Here we describe a process by which two inks are printed concomitantly in a single operation to create an alternating pattern of hydrophobic and hydrophilic characteristics...
April 4, 2018: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/29615768/anomalous-transparency-in-photonic-crystals-and-its-application-to-point-by-point-grating-inscription-in-photonic-crystal-fibers
#4
Tigran Baghdasaryan, Thomas Geernaert, Karima Chah, Christophe Caucheteur, Kay Schuster, Jens Kobelke, Hugo Thienpont, Francis Berghmans
It is common belief that photonic crystals behave similarly to isotropic and transparent media only when their feature sizes are much smaller than the wavelength of light. Here, we counter that belief and we report on photonic crystals that are transparent for anomalously high normalized frequencies up to 0.9, where the crystal's feature sizes are comparable with the free space wavelength. Using traditional photonic band theory, we demonstrate that the isofrequency curves can be circular in the region above the first stop band for triangular lattice photonic crystals...
April 3, 2018: Scientific Reports
https://www.readbyqxmd.com/read/29610091/performance-evaluation-of-cmut-based-ultrasonic-transformers-for-galvanic-isolation
#5
Jacques Heller, Audren Boulme, Daniel Alquier, Sophie Ngo, Dominique Certon
This paper presents the development of a novel acoustic transformer with high galvanic isolation dedicated to power switch triggering. The transformer is based on two capacitive micromachined ultrasonic transducers layered on each side of a silicon substrate; one is the primary circuit, and the other is the secondary circuit. The thickness mode resonance of the substrate is leveraged to transmit the triggering signal. The fabrication and characterization of an initial prototype is presented in this paper. All experimental results are discussed, from the electrical impedance measurements to the power efficiency measurements, for different electrical load conditions...
April 2018: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
https://www.readbyqxmd.com/read/29604786/note-making-tens-of-centimeter-long-uniform-microfluidic-channels-using-commercial-glass-pipette
#6
Neil Ou, Huang-Ming Lee, Jong-Ching Wu
Producing microchannels with diameters between 10 and 20 μm and with lengths in the tens of centimeters is reported. The method can be modified to obtain diameters as narrow as 350 nm. Length-to-diameter aspect ratios that surpass 104 can be produced for a fraction of current production costs. The controllable channel is produced by applying a flame to the narrow end of a commercial pipette that is made from a soda-lime silicate. In combination with a pulling mechanism, applying heat to the composite material lengthens the pipette in a highly uniform way...
March 2018: Review of Scientific Instruments
https://www.readbyqxmd.com/read/29604776/hypersonic-force-measurements-using-internal-balance-based-on-optical-micromachined-fabry-perot-interferometry
#7
Huacheng Qiu, Fu Min, Shaolong Zhong, Xin Song, Yanguang Yang
Force measurements using wind tunnel balance are necessary for determining a variety of aerodynamic performance parameters, while the harsh environment in hypersonic flows requires that the measurement instrument should be reliable and robust, in against strong electromagnetic interference, high vacuum, or metal (oxide) dusts. In this paper, we demonstrated a three-component internal balance for hypersonic aerodynamic force measurements, using novel optical micromachined Fabry-Perot interferometric (FPI) strain gauges as sensing elements...
March 2018: Review of Scientific Instruments
https://www.readbyqxmd.com/read/29603624/design-and-realization-of-3d-printed-afm-probes
#8
Nourin Alsharif, Anna Burkatovsky, Charles Lissandrello, Keith M Jones, Alice E White, Keith A Brown
Atomic force microscope (AFM) probes and AFM imaging by extension are the product of exceptionally refined silicon micromachining, but are also restricted by the limitations of these fabrication techniques. Here, the nanoscale additive manufacturing technique direct laser writing is explored as a method to print monolithic cantilevered probes for AFM. Not only are 3D printed probes found to function effectively for AFM, but they also confer several advantages, most notably the ability to image in intermittent contact mode with a bandwidth approximately ten times larger than analogous silicon probes...
March 30, 2018: Small
https://www.readbyqxmd.com/read/29570441/restricted-exchange-microenvironments-for-cell-culture
#9
Jan H Hoh, Jeffrey L Werbin, William F Heinz
Metabolite diffusion in tissues produces gradients and heterogeneous microenvironments that are not captured in standard 2D cell culture models. Here we describe restricted exchange environment chambers (REECs) in which diffusive gradients are formed and manipulated on length scales approximating those found in vivo. In REECs, cells are grown in 2D in an asymmetric chamber (<50 μL) formed between a coverglass and a glass bottom cell culture dish separated by a thin (~100 μm) gasket. Diffusive metabolite exchange between the chamber and bulk media occurs through one or more openings micromachined into the coverglass...
March 1, 2018: BioTechniques
https://www.readbyqxmd.com/read/29548071/three-bead-steering-microswimmers
#10
Mohd Suhail Rizvi, Alexander Farutin, Chaouqi Misbah
The self-propelled microswimmers have recently attracted considerable attention as model systems for biological cell migration as well as artificial micromachines. A simple and well-studied microswimmer model consists of three identical spherical beads joined by two springs in a linear fashion with active oscillatory forces being applied on the beads to generate self-propulsion. We have extended this linear microswimmer configuration to a triangular geometry where the three beads are connected by three identical springs in an equilateral triangular manner...
February 2018: Physical Review. E
https://www.readbyqxmd.com/read/29532785/radiation-characterization-and-dosimetric-measurements-of-a-femto-second-pulsed-laser-ablation-system
#11
Juan Prieto-Pena, Faustino Gomez, Diego M Gonzalez-Castano, Maria Teresa Flores Arias, Justo Arines, Carmen Bao-Varela, Ferran Cambronero-López, Alejandra Martínez Maqueira
Present work describes the radiation quality and dosimetric characterization performed on the micromachining station of the femtosecond STELA (Santiago TErawattLAser) of the University of Santiago de Compostela (Spain). For this aim, ionisation chambers, solid state detectors and radiochromic films were used. The results show the emission of pulsed X-ray produced by laser-accelerated electrons from the ablated material exhibiting both bremsstrahlung and characteristic radiation. Although this radiation was produced unintentionally, a high superficial dose rate can be achieved...
March 13, 2018: Journal of Radiological Protection: Official Journal of the Society for Radiological Protection
https://www.readbyqxmd.com/read/29521972/extended-focus-depth-for-gaussian-beam-using-binary-phase-diffractive-optical-elements
#12
Bencheikh Abdelhalim, Michael Fromager, Kamel Aït-Ameur
A novel technique to improve the focus depth of a Gaussian beam is presented in this paper. The improvement is based on two-step beam shaping using a cascade of binary phase diffractive optical elements (BPDOEs). The first BPDOE transforms the incident Gaussian beam into a high-order radial Laguerre-Gaussian beam (LGp0 ). Then the second BPDOE rectifies the obtained LGp0 beam and gives rise to a quasi-Gaussian one in the focal plane of a converging lens. This resulting quasi-Gaussian beam exhibits a lower divergence and larger focus depth compared to the pure Gaussian beam having the same beam waist...
March 10, 2018: Applied Optics
https://www.readbyqxmd.com/read/29520991/magnesium-based-micromotors-water-powered-propulsion-multifunctionality-and-biomedical-and-environmental-applications
#13
REVIEW
Chuanrui Chen, Emil Karshalev, Jianguo Guan, Joseph Wang
The new capabilities and functionalities of synthetic micro/nanomotors open up considerable opportunities for diverse environmental and biomedical applications. Water-powered micromachines are particularly attractive for realizing many of these applications. Magnesium-based motors directly use water as fuel to generate hydrogen bubbles for their propulsion, eliminating the requirement of common toxic fuels. This Review highlights the development of new Mg-based micromotors and discusses the chemistry that makes it extremely attractive for micromotor applications...
March 9, 2018: Small
https://www.readbyqxmd.com/read/29505413/monolithic-multiband-cmuts-for-photoacoustic-computed-tomography-with-in-vivo-biological-tissue-imaging
#14
Sio Hang Pun, Yuanyu Yu, Jian Zhang, Jiujiang Wang, Ching-Hsiang Cheng, Kin Fong Lei, Zhen Yuan, Peng Un Mak
Among the biomedical imaging modalities, photoacoustic computed tomography (PACT) was one of the emerging hybrid techniques in recent years. In designing the PACT imaging system, a finite-bandwidth transducer is one of the limited factors for the overall performance. As the target size is inversely proportional to the dominant frequency components of the generated photoacoustic (PA) signal, a broad bandwidth transducer is desired for different scales' imaging. In this paper, a monolithic multiband capacitive micromachined ultrasonic transducer (CMUT) array was designed and fabricated for the reception of the wideband PA signals so as to provide high-resolution images with high-frequency CMUT arrays and present the high signal-to-noise-ratio major structure with low-frequency CMUT arrays...
March 2018: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
https://www.readbyqxmd.com/read/29487375/enhanced-intracellular-delivery-via-coordinated-acoustically-driven-shear-mechanoporation-and-electrophoretic-insertion
#15
J Mark Meacham, Kiran Durvasula, F Levent Degertekin, Andrei G Fedorov
Delivery of large and structurally complex target molecules into cells is vital to the emerging areas of cellular modification and molecular therapy. Inadequacy of prevailing in vivo (viral) and in vitro (liposomal) gene transfer methods for delivery of proteins and a growing diversity of synthetic nanomaterials has encouraged development of alternative physical approaches. Efficacy of injury/diffusion-based delivery via shear mechanoporation is largely insensitive to cell type and target molecule; however, enhanced flexibility is typically accompanied by reduced gene transfer effectiveness...
February 27, 2018: Scientific Reports
https://www.readbyqxmd.com/read/29436833/photochemically-powered-agcl-janus-micromotors-as-a-model-system-to-understand-ionic-self-diffusiophoresis
#16
Chao Zhou, Hepeng Zhang, Jinyao Tang, Wei Wang
Micromotors are an emerging class of micromachines that could find potential applications in biomedicine, environmental remediation and microscale self-assembly. Understanding their propulsion mechanisms holds the key to their future development. This is especially true for a popular category of micromotors that are driven by asymmetric surface photochemical reactions. Many of these micromotors release ionic species, and are propelled via a mechanism termed ionic self-diffusiophoresis. But exactly how it operates remains vague...
February 13, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/29425440/tailoring-mechanically-tunable-strain-fields-in-graphene
#17
M Goldsche, J Sonntag, T Khodkov, Gerard Verbiest, S Reichardt, C Neumann, T Ouaj, Nils von den Driesch, Dan Buca, Christoph Stampfer
There are a number of theoretical proposals based on strain engineering of graphene and other two-dimensional materials, however purely mechanical control of strain fields in these systems has remained a major challenge. The two approaches mostly used so far either couple the electrical and mechanical properties of the system simultaneously or introduce some unwanted disturbances due to the substrate. Here, we report on silicon micromachined comb-drive actuators to controllably and reproducibly induce strain in a suspended graphene sheet, in an entirely mechanical way...
February 9, 2018: Nano Letters
https://www.readbyqxmd.com/read/29401382/micromachined-chip-scale-thermal-sensor-for-thermal-imaging
#18
Gajendra S Shekhawat, Srinivasan Ramachandran, Hossein Jiryaei Sharahi, Souravi Sarkar, Karl Hujsak, Yuan Li, Karl Hagglund, Seonghwan Kim, Gary Aden, Ami Chand, Vinayak P Dravid
The lateral resolution of scanning thermal microscopy (SThM) has hitherto never approached that of mainstream atomic force microscopy, mainly due to poor performance of the thermal sensor. Herein, we report an innovative nanomechanical system based thermal sensor (thermocouple) that enables high lateral spatial resolution that is often required in nanoscale thermal characterization in wide range of applications. This thermocouple-based probe technology delivers excellent lateral resolution (~ 20 nm), extended high temperature measurements greater than 700°C without cantilever bending, and a very high thermal sensitivity (̃~0...
February 5, 2018: ACS Nano
https://www.readbyqxmd.com/read/29393916/design-optimization-and-fabrication-of-a-novel-structural-soi-piezoresistive-pressure-sensor-with-high-accuracy
#19
Chuang Li, Francisco Cordovilla, R Jagdheesh, José L Ocaña
This paper presents a novel structural piezoresistive pressure sensor with four-grooved membrane combined with rood beam to measure low pressure. In this investigation, the design, optimization, fabrication, and measurements of the sensor are involved. By analyzing the stress distribution and deflection of sensitive elements using finite element method, a novel structure featuring high concentrated stress profile (HCSP) and locally stiffened membrane (LSM) is built. Curve fittings of the mechanical stress and deflection based on FEM simulation results are performed to establish the relationship between mechanical performance and structure dimension...
February 2, 2018: Sensors
https://www.readbyqxmd.com/read/29351210/a-high-sensitivity-electric-field-microsensor-based-on-torsional-resonance
#20
Zhaozhi Chu, Chunrong Peng, Ren Ren, Biyun Ling, Zhouwei Zhang, Hucheng Lei, Shanhong Xia
This paper proposes a high sensitivity electric field microsensor (EFM) based on torsional resonance. The proposed microsensor adopts torsional shutter, which is composed of shielding electrodes and torsional beams. The movable shielding electrodes and the fixed sensing electrodes are fabricated on the same plane and interdigitally arranged. Push-pull electrostatic actuation method is employed to excite the torsional shutter. Simulation results proved that the torsional shutter has higher efficiency of charge induction...
January 19, 2018: Sensors
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