All matter has density. The recorded uses of density to characterize matter date back to as early as ca. 250 BC, when Archimedes was believed to have solved “The Puzzle of The King's Crown” using ...density.1 Today, measurements of density are used to separate and characterize a range of materials (including cells and organisms), and their chemical and/or physical changes in time and space. This Review describes a density‐based technique—magnetic levitation (which we call “MagLev” for simplicity)—developed and used to solve problems in the fields of chemistry, materials science, and biochemistry. MagLev has two principal characteristics—simplicity, and applicability to a wide range of materials—that make it useful for a number of applications (for example, characterization of materials, quality control of manufactured plastic parts, self‐assembly of objects in 3D, separation of different types of biological cells, and bioanalyses). Its simplicity and breadth of applications also enable its use in low‐resource settings (for example—in economically developing regions—in evaluating water/food quality, and in diagnosing disease).
A density‐based technique—magnetic levitation (MagLev)—developed and used to solve problems in the fields of chemistry, materials science, and biochemistry is described in this Review. MagLev has two principal characteristics: i) it is density‐based, and thus in principle applicable to all materials, and ii) it is simple—a characteristic that makes it useful for a number of applications.
This paper describes an inexpensive, handheld device that couples the most common forms of electrochemical analysis directly to “the cloud” using any mobile phone, for use in resource-limited ...settings. The device is designed to operate with a wide range of electrode formats, performs on-board mixing of samples by vibration, and transmits data over voice using audio—an approach that guarantees broad compatibility with any available mobile phone (from low-end phones to smartphones) or cellular network (second, third, and fourth generation). The electrochemical methods that we demonstrate enable quantitative, broadly applicable, and inexpensive sensing with flexibility based on a wide variety of important electroanalytical techniques (chronoamperometry, cyclic voltammetry, differential pulse voltammetry, square wave voltammetry, and potentiometry), each with different uses. Four applications demonstrate the analytical performance of the device: these involve the detection of (i) glucose in the blood for personal health, (ii) trace heavy metals (lead, cadmium, and zinc) in water for in-field environmental monitoring, (iii) sodium in urine for clinical analysis, and (iv) a malarial antigen (Plasmodium falciparum histidine-rich protein 2) for clinical research. The combination of these electrochemical capabilities in an affordable, handheld format that is compatible with any mobile phone or network worldwide guarantees that sophisticated diagnostic testing can be performed by users with a broad spectrum of needs, resources, and levels of technical expertise.
This paper describes the design and fabrication of a “pop-up” electrochemical paper-based analytical device (pop-up-EPAD) to measure beta-hydroxybutyrate (BHB)a biomarker for diabetic ...ketoacidosisusing a commercial combination BHB/glucometer. Pop-up-EPADs are inspired by pop-up greeting cards and children’s books. They are made from a single sheet of paper folded into a three-dimensional (3D) device that changes shape, and fluidic and electrical connectivity, by simply folding and unfolding the structure. The reconfigurable 3D structure makes it possible to change the fluidic path and to control timing; it also provides mechanical support for the folded and unfolded structures that enables good registration and repeatability on folding. A pop-up-EPAD designed to detect BHB shows performance comparable to commercially available plastic test strips over the clinically relevant range of BHB in blood when used with a commercial glucometer that integrates the ability to measure glucose and BHB (combination BHB/glucometer). With simple modifications of the electrode and the design of the fluidic path, the pop-up-EPAD also detects BHB in buffer using a simple glucometera device that is more available than the combination BHB/glucometer. Strategies that use a “3D pop-up”that is, large-scale changes in 3D structure and fluidic pathsby folding/unfolding add functionality to EPADs (e.g., controlled timing, fluidic handling and path programming, control over complex sequences of steps, and alterations in electrical connectivity) and should enable the development of new classes of paper-based diagnostic devices.
In oxide semiconductors, such as those based on indium zinc oxide (IXZO), a strong oxygen binding metal ion (“oxygen getter”), X, functions to control O vacancies and enhance lattice formation, hence ...tune carrier concentration and transport properties. Here we systematically study, in the IXZO series, the role of X = Ga3+ versus the progression X = Sc3+ → Y3+ → La3+, having similar chemical characteristics but increasing ionic radii. IXZO films are prepared from solution over broad composition ranges for the first time via low-temperature combustion synthesis. The films are characterized via thermal analysis of the precursor solutions, grazing incidence angle X-ray diffraction (GIAXRD), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and scanning transmission electron microscopy (STEM) with high angle annular dark field (HAADF) imaging. Excellent thin-film transistor (TFT) performance is achieved for all X, with optimal compositions after 300 °C processing exhibiting electron mobilities of 5.4, 2.6, 2.4, and 1.8 cm2 V–1 s–1 for Ga3+, Sc3+, Y3+, and La3+, respectively, and with I on/I off = 107–108. Analysis of the IXZO TFT positive bias stress response shows X = Ga3+ to be superior with mobilities (μ) retaining >95% of the prestress values and threshold voltage shifts (ΔV T) of <1.6 V, versus <85% μ retention and ΔV T ≈ 20 V for the other trivalent ions. Detailed microstructural analysis indicates that Ga3+ most effectively promotes oxide lattice formation. We conclude that the metal oxide lattice formation enthalpy (ΔH L) and metal ionic radius are the best predictors of IXZO oxygen getter efficacy.
Polymer semiconductors have received great attention for organic electronics due to the low fabrication cost offered by solution-based printing techniques. To enable the desired ...solubility/processability and carrier mobility, polymers are functionalized with hydrocarbon chains by strategically manipulating the alkylation patterns. Note that head-to-head (HH) linkages have traditionally been avoided because the induced backbone torsion leads to poor π–π overlap and amorphous film microstructures, and hence to low carrier mobilities. We report here the synthesis of a new building block for HH linkages, 4,4′-dialkoxy-5,5′-bithiazole (BTzOR), and its incorporation into polymers for high performance organic thin-film transistors. The small oxygen van der Waals radius and intramolecular S(thiazolyl)···O(alkoxy) attraction promote HH macromolecular architectures with extensive π-conjugation, low bandgaps (1.40–1.63 eV), and high crystallinity. In comparison to previously reported 3,3′-dialkoxy-2,2′-bithiophene (BTOR), BTzOR is a promising building block in view of thiazole geometric and electronic properties: (a) replacing (thiophene)C–H with (thiazole)N reduces steric encumbrance in –BTzOR–Ar– dyads by eliminating repulsive C–H···H–C interactions with neighboring arene units, thereby enhancing π–π overlap and film crystallinity; and (b) thiazole electron-deficiency compensates alkoxy electron-donating characteristics, thereby lowering the BTzOR polymer HOMO versus that of the BTOR analogues. Thus, the new BTzOR polymers show substantial hole mobilities (0.06–0.25 cm2/(V s)) in organic thin-film transistors, as well as enhanced I on:I off ratios and greater ambient stability than the BTOR analogues. These geometric and electronic properties make BTzOR a promising building block for new classes of polymer semiconductors, and the synthetic route to BTzOR reported here should be adaptable to many other bithiazole-based building blocks.
We report the implementation of amorphous indium yttrium oxide (a-IYO) as a thin-film transistor (TFT) semiconductor. Amorphous and polycrystalline IYO films were grown via a low-temperature solution ...process utilizing exothermic “combustion” precursors. Precursor transformation and the IYO films were analyzed by differential thermal analysis, thermogravimetric analysis, X-ray diffraction, atomic force microscopy, X-ray photoelectron spectroscopy, and optical transmission, which reveal efficient conversion to the metal oxide lattice and smooth, transparent films. a-IYO TFTs fabricated with a hybrid nanodielectric exhibit electron mobilities of 7.3 cm2 V–1 s–1 (T anneal = 300 °C) and 5.0 cm2 V–1 s–1 (T anneal = 250 °C) for 2 V operation.
Significance Red blood cells with a high density (ρ > 1.120 g/cm ³) are characteristic of sickle cell disease. This paper demonstrates a density-based separation of red blood cells in a system of ...aqueous multiphase polymers that enables a visual test that identifies sickle cell disease, starting from samples of whole blood, in less than 12 min. This low-cost, simple test could provide a means to enable diagnosis of sickle cell disease in low-resource settings and enable life-saving interventions for children with the disease. The method itself provides a demonstration of the use of a biophysical indicator (here, density) rather than a biochemical marker (e.g., proteins separated by gel electrophoresis) as a means to do point-of-care hematology.
Although effective low-cost interventions exist, child mortality attributable to sickle cell disease (SCD) remains high in low-resource areas due, in large part, to the lack of accessible diagnostic methods. The presence of dense (ρ > 1.120 g/cm ³) cells is characteristic of SCD. The fluid, self-assembling step-gradients in density created by aqueous multiphase systems (AMPSs) identifies SCD by detecting dense cells. AMPSs separate different forms of red blood cells by density in a microhematocrit centrifuge and provide a visual means to distinguish individuals with SCD from those with normal hemoglobin or with nondisease, sickle-cell trait in under 12 min. Visual evaluation of a simple two-phase system identified the two main subclasses of SCD homozygous (Hb SS) and heterozygous (Hb SC) with a sensitivity of 90% (73–98%) and a specificity of 97% (86–100%). A three-phase system identified these two types of SCD with a sensitivity of 91% (78–98%) and a specificity of 88% (74–98%). This system could also distinguish between Hb SS and Hb SC. To the authors’ knowledge, this test demonstrates the first separation of cells by density with AMPSs, and the usefulness of AMPSs in point-of-care diagnostic hematology.
A solution-processed small molecule utilizing a novel 5,10-bis((2-ethylhexyl)oxy)-naphtho2,3-b:6,7-b0dithiophene corrected "zig-zag" core (zNDT) exhibits high hole mobility, upshifted frontier MO ...energies, and enhanced photovoltaic cell short-circuit currents, fill-factors, and power conversion efficiencies (4.7%) versus the linear NDT isomer.
Recent advances in polymer solar cell (PSC) performance have resulted from compressing the bandgap to enhance the short-circuit current while lowering the highest occupied molecular orbital to ...increase the open-circuit voltage. Nevertheless, PSC power conversion efficiencies are still constrained by low fill factors, typically below 70%. Here, we report PSCs with exceptionally high fill factors by combining complementary materials design, synthesis, processing and device engineering strategies. The donor polymers, PTPD3T and PBTI3T, when incorporated into inverted bulk-heterojunction PSCs with a PC71 BM acceptor, result in PSCs with fill factors of 76-80%. The enhanced performance is attributed to highly ordered, closely packed and properly oriented active-layer microstructures with optimal horizontal phase separation and vertical phase gradation. The result is efficient charge extraction and suppressed bulk and interfacial bimolecular recombination. The high fill factors yield power conversion efficiencies of up to 8.7% from polymers with suboptimal bandgaps, suggesting that efficiencies above 10% should be realizable by bandgap modification.
Organic thin film transistor (OTFT) performance is highly materials interface-dependent, and dramatic performance enhancements can be achieved by properly modifying the semiconductor/gate dielectric ...interface. However, the origin of these effects is not well understood, as this is a classic “buried interface” problem that has traditionally been difficult to address. Here we address the question of how n-octadecylsilane (OTS)–derived self-assembled monolayers (SAMs) on Si/SiO2 gate dielectrics affect the OTFT performance of the archetypical small-molecule p-type semiconductors P-BTDT (phenylbenzod,dthieno3,2-b;4,5-bdithiophene) and pentacene using combined in situ sum frequency generation spectroscopy, atomic force microscopy, and grazing incidence and reflectance X-ray scattering. The molecular order and orientation of the OTFT components at the dielectric/semiconductor interface is probed as a function of SAM growth mode in order to understand how this impacts the overlying semiconductor growth mode, packing, crystallinity, and carrier mobility, and hence, transistor performance. This understanding, using a new, humidity-specific growth procedure, leads to a reproducible, scalable process for highly ordered OTS SAMs, which in turn nucleates highly ordered p-type semiconductor film growth, and optimizes OTFT performance. Surprisingly, the combined data reveal that while SAM molecular order dramatically impacts semiconductor crystalline domain size and carrier mobility, it does not significantly influence the local orientation of the overlying organic semiconductor molecules.
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