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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
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
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
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
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
Tijana Maric, Muhammad Zafir Mohamad Nasir, Yong Wang, Bahareh Khezri, Martin Pumera
Autonomous self-propelled nano and microrobots are in the forefront of materials research. The micromachines are typically prepared in batches, stored and subsequently used. We show here that the storage of platinum tubular catalytic microrobots in water causes their corrosion which results in their lower mobility and performance. This has important implications for the construction and storage of these autonomous micromotors.
January 3, 2018: Nanoscale
Tatsuya Takeshita, Michihiro Hara
Azobenzene (1) and the complex resulting from the incorporation of 1 with cyclodextrin (1/CD) are attractive for light-driven applications such as micromachining and chemical biology tools. The highly sensitive photoresponse of 1 is crucial for light-driven applications containing both 1 and 1/CD to reach their full potential. In this study, we investigated the photoionization and trans-to-cis isomerization of 1/CD induced by one- and two-color two-laser pulse excitation. Photoionization of 1/CD, which was induced by stepwise two-photon absorption, was observed using laser pulse excitation at 266nm...
December 21, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Xiao Zhang, Xun Wu, Oluwafemi Joel Adelegan, Feysel Yalcin Yamaner, Omer Oralkan
In this paper, we describe a capacitive micromachined ultrasonic transducer (CMUT) with improved transparency for photoacoustic imaging (PAI) with backside illumination. The CMUT was fabricated on a glass substrate with indium-tin oxide bottom electrodes. The plate was a 1.5- silicon layer formed over the glass cavities by anodic bonding, with a 1- silicon nitride passivation layer on top. The fabricated device shows approximately 30%-40% transmission in the wavelength range from 700 to 800 nm and approximately 40%-60% transmission in the wavelength range from 800 to 900 nm, which correspond to the wavelength range commonly used for in vivo PAI...
January 2018: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
Hayrettin Koymen, Abdullah Atalar, Saadettin Guler, Itir Koymen, A Sinan Tasdelen, Asli Unlugedik
An energy-consistent lumped-element equivalent circuit model for charged circular capacitive micromachined ultrasonic transducer (CMUT) cell is derived and presented. It is analytically shown and experimentally verified that a series dc voltage source at the electrical terminals is sufficient to model the charging in CMUT. A model-based method for determining this potential from impedance measurements at low bias voltages is presented. The model is validated experimentally using an airborne CMUT, which resonates at 103 kHz...
January 2018: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
Bernard Shieh, Karim G Sabra, F Levent Degertekin
A hybrid boundary element model is proposed for the simulation of large piezoelectric micromachined ultrasonic transducer (PMUT) arrays in immersion. Multiphysics finite element method (FEM) simulation of a single-membrane structure is used to determine stiffness and piezoelectrically induced actuation loading of the membranes. To simulate the arrays of membranes in immersion, a boundary element method is employed, wherein membrane structures are modeled by a surface mesh that is coupled mechanically by mass, stiffness, and damping matrices, and acoustically by a mutual impedance matrix...
January 2018: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
Martin Pekař, Nenad Mihajlović, Harm Belt, Alexander F Kolen, Jeannet van Rens, Frank Budzelaar, Bas Jacobs, Johan G Bosch, Hendrik J Vos, Debbie Rem-Bronneberg, Gijs van Soest, Antonius F W van der Steen
Commercially available intracardiac echo (ICE) catheters face a trade-off between viewing depth and resolution. Frequency-tunable ICE probes would offer versatility of choice between penetration or resolution imaging within a single device. In this phantom study, the imaging performance of a novel, frequency-tunable, 32-element, 1-D CMUT array integrated with front-end electronics is evaluated. Phased-array ultrasound imaging with a forward-looking CMUT probe prototype operated beyond collapse mode at voltages up to three times higher than the collapse voltage (-65 V) is demonstrated...
December 14, 2017: Ultrasonics
Liwei Hua, Yang Song, Baokai Cheng, Wenge Zhu, Qi Zhang, Hai Xiao
This paper presents a new optical fiber distributed sensing concept based on coherent microwave-photonics interferometry (CMPI), which uses a microwave modulated coherent light source to interrogate cascaded interferometers for distributed measurement. By scanning the microwave frequencies, the complex microwave spectrum is obtained and converted to time domain signals at known locations by complex Fourier transform. The amplitudes of these time domain pulses are a function of the optical path differences (OPDs) of the distributed interferometers...
December 11, 2017: Optics Express
Maria C Ramello, Eric B Haura, Daniel Abate-Daga
Cancer immunotherapies are dramatically reshaping the clinical management of oncologic patients. For many of these therapies, the guidelines for administration, monitoring, and management of associated toxicities are still being established. This is especially relevant for adoptively transferred, genetically-modified T cells, which have unique pharmacokinetic properties, due to their ability to replicate and persist long-term, following a single administration. Furthermore, in the case of CAR-T cells, the use of synthetic immune receptors may impact signaling pathways involved in T cell function and survival in unexpected ways...
December 1, 2017: Pharmacological Research: the Official Journal of the Italian Pharmacological Society
Chao Zhou, Leilei Zhao, Mengshi Wei, Wei Wang
Micromotors powered by megahertz ultrasound, first reported about 5 years ago, have lately been considered a promising platform for a wide range of microscale applications, yet we are only at the early stage of understanding their operating mechanisms. Through carefully designed experiments, and by comparing the results to acoustic theories, we present here an in-depth study of the behaviors of particles activated by ultrasound, especially their in-plane orbiting and spinning dynamics. Experiments suggest that metallic micro-rods orbit in tight circles near the resonance ultrasound frequency, likely driven by localized acoustic streaming due to slightly bent particle shapes...
November 28, 2017: ACS Nano
Jun Woo Bae, Hee Reyoung Kim
BACKGROUND: Anti-scattering grid has been used to improve the image quality. However, applying a commonly used linear or parallel grid would cause image distortion, and focusing grid also requires a precise fabrication technology, which is expensive. OBJECTIVE: To investigate and analyze whether using CO2 laser micromachining-based PMMA anti-scattering grid can improve the performance of the grid at a lower cost. Thus, improvement of grid performance would result in improvement of image quality...
November 16, 2017: Journal of X-ray Science and Technology
Tural Khudiyev, Jefferson Clayton, Etgar Levy, Noémie Chocat, Alexander Gumennik, Alexander M Stolyarov, John Joannopoulos, Yoel Fink
Microelectromechanical systems (MEMS) enable many modern-day technologies, including actuators, motion sensors, drug delivery systems, projection displays, etc. Currently, MEMS fabrication techniques are primarily based on silicon micromachining processes, resulting in rigid and low aspect ratio structures. In this study, we report on the discovery of MEMS functionality in fibres, thereby opening a path towards flexible, high-aspect ratio, and textile MEMS. The method used for generating these MEMS fibres leverages a preform-to-fibre thermal drawing process, in which the MEMS architecture and materials are embedded into a preform and drawn into kilometers of microstructured multimaterial fibre devices...
November 10, 2017: Nature Communications
Sandeep Keshavan, Shovan Naskar, Alberto Diaspro, Laura Cancedda, Silvia Dante
Interfacing neurons with a single atomic layer of graphene, single atomic layer of sp2 hybridized C-atoms, is a key paradigm in understanding how to exploit the unique properties of such a two-dimensional system for neural prosthetics and biosensors development. In order to fabricate graphene-based circuitry, a reliable large area patterning method is a requirement. Following a previously developed protocol, we monitored the in vitro neuronal development of geometrically ordered neural network growing onto patterned Single Layer Graphene (SLG) coated with poly-D-lysine...
November 6, 2017: Acta Biomaterialia
Jian Zhang, Sio Hang Pun, Yuanyu Yu, Duyang Gao, Jiujiang Wang, Peng Un Mak, Kin Fong Lei, Ching-Hsiang Cheng, Zhen Yuan
Photoacoustic tomography (PAT) as a hybrid technology combines the high optical contrast and high acoustic resolution in a single imaging modality. However, most of the available PAT systems cannot comprehensively or accurately characterize biological systems at multiple length scales due to the use of narrow bandwidth commercial ultrasonic transducers. In this study, we fabricated a novel multi-band capacitive micromachined ultrasonic transducer (CMUT) array, and first developed a CMUT-based multi-band photoacoustic tomography (MBPAT) imaging system...
May 10, 2017: Applied Optics
Maëva Vallet, François Varray, Jérôme Boutet, Jean-Marc Dinten, Giosuè Caliano, Alessandro Stuart Savoia, Didier Vray
Photoacoustic (PA) signals are short ultrasound (US) pulses typically characterized by a single-cycle shape, often referred to as N-shape. The spectral content of such wideband signals ranges from a few hundred kilohertz to several tens of megahertz. Typical reception frequency responses of classical piezoelectric US imaging transducers, based on PZT technology, are not sufficiently broadband to fully preserve the entire information contained in PA signals, which are then filtered, thus limiting PA imaging performance...
December 2017: Photoacoustics
Tyler A Morhart, Bipinlal Unni, Michael J Lardner, Ian J Burgess
Thin, micromachined Si wafers, designed as internal reflection elements (IREs) for attenuated total reflectance infrared spectroscopy, are adapted to serve as substrates for electrochemical ATR surface enhanced infrared absorption spectroscopy (ATR-SEIRAS). The 500 μm thick wafer IREs with groove angles of 35° are significantly more transparent at long mid-IR wavelengths as compared to conventional large Si hemisphere IREs. The appeal of greater transparency is mitigated by smaller optical throughput at larger grazing angles and steeper angles of incidence at the reflecting plane that reduce the enhancement factor...
November 7, 2017: Analytical Chemistry
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