2,765 research outputs found
A Paper-Based Calorimetric Microfluidics Platform for Bio-chemical Sensing
In this report, a paper-based micro-calorimetric biochemical detection method is presented. Calorimetric detection of biochemical reactions is demonstrated as an extension of current colorimetric and electrochemical detection mechanisms of paper-based biochemical analytical systems. Reaction and/or binding temperature of glucose/glucose oxidase, DNA/hydrogen peroxide, and biotin/streptavidin, are measured by the paper-based micro-calorimeter. Commercially available glucose calibration samples of 0.05, 0.15 and 0.3% wt/vol concentration are used for comparing the device performance with a commercially available glucose meter (electrochemical detection). The calorimetric glucose detection demonstrates a measurement error less than 2%. The calorimetric detection results of DNA concentrations from 0.9 to 7.3 mg/mL and temperature changes in biotin and streptavidin reaction are presented to demonstrate the feasibility of integrating the calorimetric detection method with paper based microfluidic devices
Cooper-Pair Spin Current in a Strontium Ruthenate Heterostructure
It has been recognized that the condensation of spin-triplet Cooper pairs
requires not only the broken gauge symmetry but also the spin ordering as well.
One consequence of this is the possibility of the Cooper-pair spin current
analogous to the magnon spin current in magnetic insulators, the analogy also
extending to the existence of the Gilbert damping of the collective
spin-triplet dynamics. The recently fabricated heterostructure of the thin film
of the itinerant ferromagnet SrRuO3 on the bulk Sr2RuO4, the best-known
candidate material for the spin-triplet superconductor, offers a promising
platform for generating such spin current. We will show how such
heterostructure allows us to not only realize the long-range spin valve but
also electrically drive the collective spin mode of the spin-triplet order
parameter. Our proposal represents both a new realization of the spin
superfluidity and a transport signature of the spin-triplet superconductivity.Comment: 5 pages, 3 figure
Magnon topology and thermal Hall effect in trimerized triangular lattice antiferromagnet
The non-trivial magnon band topology and its consequent responses have been
extensively studied in two-dimensional magnetisms. However, the triangular
lattice antiferromagnet (TLAF), the best-known frustrated two-dimensional
magnet, has received less attention than the closely related Kagome system,
because of the spin-chirality cancellation in the umbrella ground state of the
undistorted TLAF. In this work, we study the band topology and the thermal Hall
effect (THE) of the TLAF with (anti-)trimerization distortion under the
external perpendicular magnetic field using the linearized spin wave theory. We
show that the spin-chirality cancellation is removed in such case, giving rise
to the non-trivial magnon band topology and the finite THE. Moreover, the
magnon bands exhibit band topology transitions tuned by the magnetic field. We
demonstrate that such transitions are accompanied by the logarithmic divergence
of the first derivative of the thermal Hall conductivity. Finally, we examine
the above consequences by calculating the THE in the hexagonal manganite
YMnO, well known to have anti-trimerization.Comment: 6 + 7 pages, 3 + 5 figures, 0 + 1 table; Journal reference adde
6.4 GHz Acoustic Sensor for In-situ Monitoring of AFM Tip Wear
This paper demonstrates an acoustic sensor that can resolve atomic force microscopy (AFM) tip blunting with a frequency sensitivity of 0.007%. The AFM tip is fabricated on a thin film piezoelectric aluminum nitride (AlN) membrane that is excited as a film bulk acoustic resonator (FBAR). We demonstrate that cutting 0.98 μm off of the tip apex results in a resonance frequency change of 0.4MHz at 6.387GHz. This work demonstrates the potential for in-situ monitoring of AFM tip wear
A Suspended Nanogap Formed by Field-Induced Atomically Sharp Tips
A sub-nanometer scale suspended gap (nanogap) defined by electric field-induced atomically sharp metallic tips is presented. A strong local electric field (\u3e109 V=m) across micro/nanomachined tips facing each other causes the metal ion migration in the form of dendrite-like growth at the cathode. The nanogap is fully isolated from the substrate eliminating growth mechanisms that involve substrate interactions. The proposed mechanism of ion transportation is verified using real-time imaging of the metal ion transportation using an in situ biasing in transmission electron microscope (TEM). The configuration of the micro/nanomachined suspended tips allows nanostructure growth of a wide variety of materials including metals, metal-oxides, and polymers. VC 2012 American Institute of Physics
Integrated Freestanding Single-Crystal Silicon Nanowires: Conductivity and Surface Treatment
Integrated freestanding single-crystal silicon nanowires with typical dimension of 100 nm × 100 nm × 5 µm are fabricated by conventional 1:1 optical lithography and wet chemical silicon etching. The fabrication procedure can lead to wafer-scale integration of silicon nanowires in arrays. The measured electrical transport characteristics of the silicon nanowires covered with/without SiO2 support a model of Fermi level pinning near the conduction band. The I–V curves of the nanowires reveal a current carrier polarity reversal depending on Si–SiO2 and Si–H bonds on the nanowire surface
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