A hybrid approach to solar cells is demonstrated in which a silicon p–n junction, used in conventional silicon‐based photovoltaics, is replaced by a room‐temperature fabricated silicon/organic ...heterojunction. The unique advantage of silicon/organic heterojunction is that it exploits the cost advantage of organic semiconductors and the performance advantages of silicon to enable potentially low‐cost, efficient solar cells.
The KZN strain family of Mycobacterium tuberculosis is a highly virulent strain endemic to the KwaZulu-Natal region of South Africa, which has recently experienced an outbreak of extensively-drug ...resistant tuberculosis. To investigate the causes and evolution of drug-resistance, we determined the DNA sequences of several clinical isolates--one drug-susceptible, one multi-drug resistant, and nine extensively drug-resistant--using whole-genome sequencing. Analysis of polymorphisms among the strains is consistent with the drug-susceptibility profiles, in that well-known mutations are observed that are correlated with resistance to isoniazid, rifampicin, kanamycin, ofloxacin, ethambutol, and pyrazinamide. However, the mutations responsible for rifampicin resistance in rpoB and pyrazinamide in pncA are in different nucleotide positions in the multi-drug-resistant and extensively drug-resistant strains, clearly showing that they acquired these mutations independently, and that the XDR strain could not have evolved directly from the MDR strain (though it could have arisen from another similar MDR strain). Sequencing of eight additional XDR strains from other areas of KwaZulu-Natal shows that they have identical drug resistant mutations to the first one sequenced, including the same polymorphisms at sites associated with drug resistance, supporting the theory that this represents a case of clonal expansion.
We report on a microfluidic particle-separation device that makes use of the asymmetric bifurcation of laminar flow around obstacles. A particle chooses its path deterministically on the basis of its ...size. All particles of a given size follow equivalent migration paths, leading to high resolution. The microspheres of 0.8, 0.9, and 1.0 micrometers that were used to characterize the device were sorted in 40 seconds with a resolution of ~10 nanometers, which was better than the time and resolution of conventional flow techniques. Bacterial artificial chromosomes could be separated in 10 minutes with a resolution of ~12%.
Reconfigurable antennas introduce unique and dynamic system capabilities for wireless communication and sensing, by enabling controllable radiation pattern, frequency response, and polarization of ...electromagnetic (EM) waves. The antenna's physical dimensions are critical to enhancing control of radiative characteristics, making it necessary to distribute RF control devices across a large-area aperture. Previous reconfigurable antennas have been limited in scale and performance by the need to assemble discrete active components. Large-area electronics (LAE) is a technology that can enable monolithic reconfigurable antennas, with flexible and large form factors. However, conventionally the speed of LAE, specifically of thin-film transistors (TFTs), has been restricted to 10-100 MHz. In this work, a reconfigurable antenna based on LAE RF TFTs is achieved through a combination of: 1) materials and device enhancements pushing fundamental TFT performance metrics to the giga-Hertz regime and 2) an architecture that employs the TFTs as passive switches, rather than active amplifiers, to enable aggressive biasing for high-frequency operation, yet within the breakdown limits. A 9 <inline-formula> <tex-math notation="LaTeX">\times </tex-math></inline-formula> 9 cm2 reconfigurable antenna consisting of an 11 <inline-formula> <tex-math notation="LaTeX">\times </tex-math></inline-formula> 11 array of metal patches as sub-radiators controlled by 208 TFT-based RF switches is demonstrated. Far-field and <inline-formula> <tex-math notation="LaTeX">S </tex-math></inline-formula>-parameter measurements show reconfigured beam steering by 90° and resonant-frequency tuning by 200 MHz.
Circulating tumor cells (CTCs) and circulating clusters of cancer and stromal cells have been identified in the blood of patients with malignant cancer and can be used as a diagnostic for disease ...severity, assess the efficacy of different treatment strategies and possibly determine the eventual location of metastatic invasions for possible treatment. There is thus a critical need to isolate, propagate and characterize viable CTCs and clusters of cancer cells with their associated stroma cells. Here, we present a microfluidic device for mL/min flow rate, continuous-flow capture of viable CTCs from blood using deterministic lateral displacement (DLD) arrays. We show here that a DLD array device can isolate CTCs from blood with capture efficiency greater than 85% CTCs at volumetric flow rates of up to 10 mL/min with no effect on cell viability.
Damage significantly influences response of a strain sensor only if it occurs in the proximity of the sensor. Thus, two-dimensional (2D) sensing sheets covering large areas offer reliable early-stage ...damage detection for structural health monitoring (SHM) applications. This paper presents a scalable sensing sheet design consisting of a dense array of thin-film resistive strain sensors. The sensing sheet is fabricated using flexible printed circuit board (Flex-PCB) manufacturing process which enables low-cost and high-volume sensors that can cover large areas. The lab tests on an aluminum beam showed the sheet has a gauge factor of 2.1 and has a low drift of 1.5 μ ϵ / d a y . The field test on a pedestrian bridge showed the sheet is sensitive enough to track strain induced by the bridge's temperature variations. The strain measured by the sheet had a root-mean-square (RMS) error of 7 μ ϵ r m s compared to a reference strain on the surface, extrapolated from fiber-optic sensors embedded within the bridge structure. The field tests on an existing crack showed that the sensing sheet can track the early-stage damage growth, where it sensed 600 μ ϵ peak strain, whereas the nearby sensors on a damage-free surface did not observe significant strain change.
Electrically-driven soft robots based on piezoelectric actuators may enable compact form factors and maneuverability in complex environments. In most prior work, piezoelectric actuators are used to ...control a single degree of freedom. In this work, the coordinated activation of five independent piezoelectric actuators, attached to a common metal foil, is used to implement inchworm-inspired crawling motion in a robot that is less than 0.5 mm thick. The motion is based on the control of its friction to the ground through the robot's shape, in which one end of the robot (depending on its shape) is anchored to the ground by static friction, while the rest of its body expands or contracts. A complete analytical model of the robot shape, which includes gravity, and contact is developed to quantify the robot shape, friction, and displacement. After validation of the model by experiments, the robot's five actuators are collectively sequenced for inchworm-like forward and backward motion.
The classical SiO2/Si interface, which is the basis of integrated circuit technology, is prepared by thermal oxidation followed by high temperature (>800 °C) annealing. Here we show that an interface ...synthesized between titanium dioxide (TiO2) and hydrogen-terminated silicon (H:Si) is a highly efficient solar cell heterojunction that can be prepared under typical laboratory conditions from a simple organometallic precursor. A thin film of TiO2 is grown on the surface of H:Si through a sequence of vapor deposition of titanium tetra(tert-butoxide) (1) and heating to 100 °C. The TiO2 film serves as a hole-blocking layer in a TiO2/Si heterojunction solar cell. Further heating to 250 °C and then treating with a dilute solution of 1 yields a hole surface recombination velocity of 16 cm/s, which is comparable to the best values reported for the classical SiO2/Si interface. The outstanding performance of this heterojunction is attributed to Si–O–Ti bonding at the TiO2/Si interface, which was probed by angle-resolved X-ray photoelectron spectroscopy. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) showed that Si–H bonds remain even after annealing at 250 °C. The ease and scalability of the synthetic route employed and the quality of the interface it provides suggest that this surface chemistry has the potential to enable fundamentally new, efficient silicon solar cell devices.
This paper presents an electroencephalogram (EEG) acquisition and biomarker-extraction system based on flexible, thin-film electronics. There exist commercial, single-use, flexible, pre-gelled ...electrode arrays; however, these are fully passive, requiring cabling to transfer sensitive, low-amplitude signals to external electronics for readout and processing. This work presents an active EEG acquisition system on flex, based on amorphous silicon (a-Si) thin-film transistors (TFTs). The system incorporates embedded chopper-stabilized a-Si TFT low-noise amplifiers, to enhance signal integrity, and a-Si TFT compressive-sensing scanning circuits, to enable reduction of EEG data from many channels onto a single interface, for subsequent processing by a CMOS IC. Further, the system uses an algorithm, by which spectral-energy features, a key EEG biomarker, are extracted directly from the compressed signals. We demonstrate a prototype, performing EEG acquisition from a human subject, and compressed EEG data. The TFT amplifier achieves a noise PSD of 230 nV/√Hz. reconstruction and seizure detection via analog replay of patient Seizure detection, at up to 64× compression, achieves error rates <;8%. Reconstruction is demonstrated at up to 8× compression.
Deterministic hydrodynamics: Taking blood apart Davis, John A; Inglis, David W; Morton, Keith J ...
Proceedings of the National Academy of Sciences - PNAS,
10/2006, Letnik:
103, Številka:
40
Journal Article
Recenzirano
Odprti dostop
We show the fractionation of whole blood components and isolation of blood plasma with no dilution by using a continuous-flow deterministic array that separates blood components by their hydrodynamic ...size, independent of their mass. We use the technology we developed of deterministic arrays which separate white blood cells, red blood cells, and platelets from blood plasma at flow velocities of 1,000 μm/sec and volume rates up to 1 μl/min. We verified by flow cytometry that an array using focused injection removed 100% of the lymphocytes and monocytes from the main red blood cell and platelet stream. Using a second design, we demonstrated the separation of blood plasma from the blood cells (white, red, and platelets) with virtually no dilution of the plasma and no cellular contamination of the plasma. cells plasma separation microfabrication
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