Volume 78, Issue 7, July 2007
- special topic: instruments and methods for combinatorial science and high-throughput screening
- optics; atoms and molecules; spectroscopy; photon detectors
- particle sources, optics and acceleration; particle detectors
- nuclear physics, fusion and plasmas
- microscopy and imaging
- condensed matter; materials
- biology and medicine
- electronics; electromagnetic technology; microwaves
- thermometry; thermal diffusivity; acoustic; photothermal and photoacoustic
- general instruments
Index of content:
- SPECIAL TOPIC: INSTRUMENTS AND METHODS FOR COMBINATORIAL SCIENCE AND HIGH-THROUGHPUT SCREENING
Preface to Special Topic: Instruments and methods for combinatorial science and high-throughput screening78(2007); http://dx.doi.org/10.1063/1.2754653View Description Hide Description
78(2007); http://dx.doi.org/10.1063/1.2755569View Description Hide Description
Five designs for a miniaturized dynamic light scattering (DLS) instrument are described that incorporate microfluidic flow of the sample volume and fiber optic probes directly embedded into the sample. These instruments were demonstrated to accurately determine the size of particles dispersed in organic and aqueous solvents with most sample sizes less than . Small stir bars were incorporated directly into the instruments, and enabled blending of different solutions immediately prior to DLS measurements. Demonstration of the instruments’ capabilities include high throughput measurements of the micelle to unimer transition for poly(styrene--isoprene) in mixed toluene/hexadecane solvent, obtained by systematically blending toluene-rich and hexadecane-rich polymer solutions. The critical solvent composition was quickly identified with less than of polymer. Further capabilities include temperature control, demonstrated by identification of a critical micelle temperature of poly(ethylene oxide--propylene oxide--ethylene oxide), as well as multiangle DLS measurements.
78(2007); http://dx.doi.org/10.1063/1.2755729View Description Hide Description
This article details the design, construction, and operation of flexible system that modulates light exposure for the purpose of fabricating continuous and discrete gradient combinatorial libraries. Designed for versatility, the device combines “off the shelf” components, modular accessories, and flexible computer control, so that it can be used for a variety of combinatorial research applications. Salient aspects and capabilities of the instrument are illustrated through two practical examples. The first case demonstrates how user defined exposure functions can be used to create continuous surface energy gradient libraries with a linear profile. The second example illustrates the creation of continuous and discrete libraries for mapping exposure-property functions in a photocurable polymer system.
Model, prediction, and experimental verification of composition and thickness in continuous spread thin film combinatorial libraries grown by pulsed laser deposition78(2007); http://dx.doi.org/10.1063/1.2755783View Description Hide Description
Pulsed laser deposition was used to grow continuous spread thin film libraries of continuously varying composition as a function of position on a substrate. The thickness of each component that contributes to a library can be empirically modeled to a bimodal cosine power distribution. We deposited ternary continuous spread thin film libraries from , , and targets, at two different background pressures of : 1.3 and . Prior to library deposition, we deposited single component calibrationfilms at both pressures in order to measure and fit the thickness distribution. Following the deposition and fitting of the single component films, we predict both the compositional coverage and the thickness of the libraries. Then, we map the thickness of the continuous spread libraries using spectroscopic reflectometry and measure the composition of the libraries as a function of position using mapping wavelength-dispersive spectrometry (WDS). We then compare the compositional coverage of the libraries and observe that compositional coverage is enhanced in the case of library. Our models demonstrate linear correlation coefficients of 0.98 for and 0.98 for with the WDS.
Combinatorial materials research applied to the development of new surface coatings VI: An automated spinning water jet apparatus for the high-throughput characterization of fouling-release marine coatings78(2007); http://dx.doi.org/10.1063/1.2755965View Description Hide Description
Large numbers of coatings can be generated very quickly using a combinatorial high-throughput approach. Rapid screening assays are typically required to adequately evaluate and down select coating candidates to identify promising compositions. An automated, spinning water jet apparatus was developed to rapidly characterize the adhesion strength of marine organisms to coating surfaces. Coating arrays are cast in multiwell plates and subjected to a jet of water of controlledpressure and duration. Array plates are manipulated by a robotic arm to facilitate accurate and repeatable water jet treatments. Jet pressures of can be generated and precisely maintained by computer control. A five axis robotic arm selects plates from three plate stacking hotels yielding a total of 39 plates or 936 individual coating samples for each experimental run. All robotic instructions, process parameters, and data are stored and controlled by the computer. The large plate handling capacity offered by the robotic system enables the analysis of a wide variety of coatings for “fouling-release” properties. A brief example demonstrating the capability of the automated water jet apparatus to evaluate marine bacterial adhesion to coating surfaces is provided.
Combined micro-Raman/UV-visible/fluorescence spectrometer for high-throughput analysis of microsamples78(2007); http://dx.doi.org/10.1063/1.2755745View Description Hide Description
Combined micro-Raman/UV-visible (vis)/fluorescence spectroscopy system, which can evaluate an integrated array of more than 10 000 microsamples with a minimuma size of within a few hours, has been developed for the first time. The array of microsamples is positioned on a computer-controlled translation microstage with a spatial resolution of so that the spectra can be mapped with micron precision. Micro-Raman spectrometers have a high spectral resolution of about over the wave number range of , while UV-vis and fluorescence spectrometers have high spectral resolutions of 0.4 and over the wavelength range of , respectively. In particular, the signal-to-noise ratio of the micro-Raman spectroscopy has been improved by using a holographic Raman grating and a liquid-nitrogen-cooled charge-coupled device detector. The performance of the combined spectroscopy system has been demonstrated by the high-throughput screening of a combinatorial ferroelectric (i.e., ) library. This system makes possible the structure analysis of various materials including ferroelectrics, catalysts, phosphors, polymers, alloys, and so on for the development of novel materials and the ultrasensitive detection of trace amounts of pharmaceuticals and diagnostic agents.
78(2007); http://dx.doi.org/10.1063/1.2755776View Description Hide Description
We describe high-throughput experimentation of film synthesis by use of a linear tape transport system (similar to a web-coating system). Metal tape is fed continuously in a reel-to-reel transport system inside the vacuum depositionchamber.Ion-beam assisted deposition (IBAD) texturing is used to enable the growth of epitaxialfilms on flexible, polycrystalline metal tapes which further enhances the capability of this research. The tape that is continuously fed can be used as a sample itself, via the use of IBAD-textured templates on the tape, or can be a carrier of other smaller substrates (even nonflexible ones). Characterization of samples is done by means of in situ monitoring as well as ex situ sequential analysis. We utilize in situreflection high-energy electron diffraction for high-throughput analysis of samples. Epitaxialfilms are deposited on heated samples by evaporation and by pulsed laser deposition. Here, we explain the techniques and the methodologies developed for this type of combinatorial experimentation and show some examples of the material research completed.
78(2007); http://dx.doi.org/10.1063/1.2755761View Description Hide Description
We have designed a novel combinatorial research platform to help accelerate tissue engineering research. Combinatorial methods combine many samples into a single specimen to enable accelerated experimentation and discovery. The platform for fabricating combinatorial polymer scaffold libraries can be used to rapidly identify scaffold formulations that maximize tissue formation. Many approaches for screening cell-biomaterial interactions utilize a two-dimensional format such as a film or surface to present test substrates to cells. However, cellsin vivo exist in a three-dimensional milieu of extracellular matrix and cellsin vitro behave more naturally when cultured in a three-dimensional environment than when cultured on a two-dimensional surface. Thus, we have designed a method for fabricating combinatorial biomaterial libraries where the materials are presented to cells in the form of three-dimensional, porous, salt-leached, polymer scaffolds. Many scaffold variations and compositions can be screened in a single experiment so that optimal scaffold formulations for tissue formation can be rapidly identified. In summary, we have developed a platform technology for fabricating combinatorial polymer scaffold libraries that can be used to screen cell response to materials in a three-dimensional, scaffold format.
78(2007); http://dx.doi.org/10.1063/1.2755779View Description Hide Description
We investigate the stresses in thin films with sub-millimeter lateral spatial resolution using a dense array of prefabricated cantilever beams prepared by microelectromechanical-system techniques. Stress induced deflection of the cantilever is interrogated by an optical (laser/position sensitive detector) measurement system. Composition spread films are deposited on the cantilever array using a three gun on-axis magnetron cosputtering system. The position dependent composition is inferred using rate calibrations and verified by electron microprobe/energy dispersive spectroscopy. We demonstrate the function of this system using an Fe–Ni–Al composition spread with resolution. This approach allows for measurement of the composition dependence of other electromechanical properties such as the martensitic phase transition temperature of traditional and ferromagnetic shape-memory alloys, as well as the properties of hydrogen storagematerials and the magnetic response of magnetostrictive materials.
Combinatorial electrochemical cell array for high throughput screening of micro-fuel-cells and metal/air batteries78(2007); http://dx.doi.org/10.1063/1.2755439View Description Hide Description
An electrochemicalcell array was designed that contains a common air electrode and 16 microanodes for high throughput screening of both fuel cells (based on polymer electrolyte membrane) and metal/air batteries (based on liquid electrolyte).Electrode materials can easily be coated on the anodes of the electrochemicalcell array and screened by switching a graphite probe from one cell to the others. The electrochemicalcell array was used to study direct methanol fuel cells (DMFCs), including high throughput screening of electrode catalysts and determination of optimum operating conditions. For screening of DMFCs, there is about 6% relative standard deviation (percentage of standard deviation versus mean value) for discharge current from . The electrochemicalcell array was also used to study tin/air batteries. The effect of Cu content in the anodeelectrode on the discharge performance of the tin/air battery was investigated. The relative standard deviations for screening of metal/air battery (based on zinc/air) are 2.4%, 3.6%, and 5.1% for discharge current at 50, 100, and , respectively.
Protocols for printing thick film ceramic libraries using the London University Search Instrument (LUSI)78(2007); http://dx.doi.org/10.1063/1.2755469View Description Hide Description
Thick film combinatorial libraries can be prepared by mixingceramicsuspensions using stepper-driven syringes to control ink-jet-printing nozzles, but a more tolerant and efficient method has been devised using a simplification of the same equipment. By simplifying the printing sequence and using direct deposition from the stepper syringes, the time committed to a repetitive sequence of priming and cleaning the ink-jet printer nozzles is reduced. Polytetrafluoroethylene (PTFE) open ended tubes and commercial pipette tips are used as the printing nozzles. Calibration and corrections for the method are described. This method opens up the possibility for making ceramic libraries more rapidly with much simpler and less expensive equipment.
High-throughput reactor system with individual temperature control for the investigation of monolith catalysts78(2007); http://dx.doi.org/10.1063/1.2755781View Description Hide Description
A high-throughput parallel reactor system has been designed and constructed to improve the reliability of results from large diameter catalysts such as monoliths. The system, which is expandable, consists of eight quartz reactors, in diameter. The eight reactors were designed with separate type thermocouples and radiant heaters, allowing for the independent measurement and control of each reactor temperature. This design gives steady state temperature distributions over the eight reactors within of a common setpoint from . Analysis of the effluent from these reactors is performed using rapid-scan Fourier transform infrared (FTIR)spectroscopic imaging. The integration of this technique to the reactor system allows a chemically specific, truly parallel analysis of the reactor effluents with a time resolution of approximately . The capabilities of this system were demonstrated via investigation of catalyst preparation conditions on the direct epoxidation of ethylene, i.e., on the ethylene conversion and the ethylene oxide selectivity. The ethylene, ethylene oxide, and carbon dioxide concentrations were calibrated based on spectra from FTIR imaging using univariate and multivariate chemometric techniques. The results from this analysis showed that the calcination conditions significantly affect the ethylene conversion, with a threefold increase in the conversion when the catalyst was calcined for versus at .
78(2007); http://dx.doi.org/10.1063/1.2755967View Description Hide Description
We describe a sputtering system that can deposit composition spreads in an effectively UHV environment but which does not require the high-throughput paradigm to be compromised by a long pump down each time a target is changed. The system deploys four magnetron sputter guns in a cryoshroud (getter sputtering) which allows elements such as Ti and Zr to be deposited with minimal contamination by oxygen or other reactive background gases. The system also relies on custom substrate heaters to give rapid heating and cool down. The effectiveness of the gettering technique is evaluated, and example results obtained for catalytic activity of a pseudoternary composition spread are presented.
Combinatorial materials research applied to the development of new surface coatings VII: An automated system for adhesion testing78(2007); http://dx.doi.org/10.1063/1.2755505View Description Hide Description
An automated, high-throughput adhesion workflow that enables pseudobarnacle adhesion and coating/substrate adhesion to be measured on coating patches arranged in an array format on panels was developed. The adhesion workflow consists of the following process steps: (1) application of an adhesive to the coating array; (2) insertion of panels into a clamping device; (3) insertion of aluminum studs into the clamping device and onto coating surfaces, aligned with the adhesive; (4) curing of the adhesive; and (5) automated removal of the aluminum studs. Validation experiments comparing data generated using the automated, high-throughput workflow to data obtained using conventional, manual methods showed that the automated system allows for accurate ranking of relative coatingadhesion performance.
78(2007); http://dx.doi.org/10.1063/1.2755657View Description Hide Description
Screening of materials arrays for their viscoelastic, gas-sorbing, and dielectric properties is important in a wide variety of combinatorial materials science applications. Impedance analysis is an attractive approach to analyze these materials properties and to generate the required new knowledge. Often, these measurements are performed by applying a material onto a suitable sensor and monitoring the changes in materials properties. However, when such a sensor is positioned into a test cell, a direct-wired connection to the analyzer becomes complicated. These complications further increase dramatically when a whole array of sensors is being tested in the test cell. To eliminate these complications, we developed a wireless proximity resonant sensor array system. In the developed system, tested materials are applied onto an array of thickness-shear mode (TSM) resonators operating at and arranged for performance testing in a test chamber. Each TSM resonator is coupled to a receiver coil (antenna). An array of these coils is read with a single scanning transmitter coil or an array of transmitter coils. This high-throughput screening approach of sensing materials permits their evaluation in complex environments where additional wiring is not desirable or adds a prohibitively complex design. We demonstrated the applicability of the wireless sensormaterials screening approach for the rapid evaluation of the effects of conditioning of polymeric sensing films at different temperatures on the vapor-response patterns to several vapors of industrial, health, law enforcement, and security interest (ethanol, acetonitrile, and water vapors).
78(2007); http://dx.doi.org/10.1063/1.2755693View Description Hide Description
Combinatorial materials libraries are becoming more complicated; successful screening of these libraries requires the development of new high throughput screening methodologies. Time of flight secondary ion mass spectrometry (ToF-SIMS) is a surface analytical technique that is able to detect and image all elements (including hydrogen which is problematic for many other analysis instruments) and molecular fragments, with high mass resolution, during a single measurement. Commercial ToF-SIMS instruments can image areas by rastering the primary ion beam over the region of interest. In this work, we will show that large area analysis can be performed, in one single measurement, by rastering the sample under the ion beam. We show that an entire diameter wafer can be imaged in less than using ToF-SIMS stage (macro)rastering techniques. ToF-SIMS data sets contain a wealth of information since an entire high mass resolution mass spectrum is saved at each pixel in an ion image. Multivariate statistical analysis (MVSA) tools are being used in the ToF-SIMS community to assist with data interpretation; we will demonstrate that MVSA tools provide details that were not obtained using manual (univariate) analysis.
78(2007); http://dx.doi.org/10.1063/1.2756993View Description Hide Description
In this article we present a setup for the combinatorial vapor deposition of thin-film multilayer devices as well as methods for the fast and efficient analytic screening of the libraries obtained. The preparation setup is based on a commercially available evaporation chamber equipped with various evaporation sources for both organic and metallic materials. The combinatorial approach is realized by the combination of a rotation stage for the substrate, a five-mask sampler, and an additional mask whose position can be deliberately varied along one axis during the evaporation process. The latter is used to evaporate linear as well as step gradients by continuous or stepwise movement of a shutter mask. The mask sampler allows to define the sectors of the library and to evaporate more complex structures, e.g., an electrode layout. Finally, the simultaneous evaporation of two or more materials enables us to produce layers of varying composition ratio in general and dopedmaterials, in particular. For the control of the evaporation process we have developed an automation software, which is particularly helpful for complex library designs and which grants excellent repeatability of experiments. Efficient and fast characterization of the obtained libraries is realized by (i) a purely optical setup and (ii) an electro-optical setup. (i) The UV/vis reader FLASHScan® 530 permits to map out the UV/vis absorbance or fluorescence of the whole library. The UV/vis absorbance is primarily used to determine layer thicknesses and to confirm thickness uniformity across larger regions. The fluorescence measurements are used to determine the composition of layers containing fluorescent dyes. (ii) For a detailed short- and long-term electro-optical analysis we have developed an automated measurement system, which allows the characterization of optoelectronic devices and to study their degradation behavior. Both solar cells and organic light-emitting diodes can be tested. Finally, we have developed a data analysis software to extract characteristic values from the huge amount of data and with this facilitate the finding of systematic dependencies.
Rapid structural mapping of ternary metallic alloy systems using the combinatorial approach and cluster analysis78(2007); http://dx.doi.org/10.1063/1.2755487View Description Hide Description
We are developing a procedure for the quick identification of structural phases in thin film composition spread experiments which map large fractions of compositional phase diagrams of ternary metallic alloy systems. An in-house scanning x-ray microdiffractometer is used to obtain x-ray spectra from 273 different compositions on a single composition spread library. A cluster analysissoftware is then used to sort the spectra into groups in order to rapidly discover the distribution of phases on the ternary diagram. The most representative pattern of each group is then compared to a database of known structures to identify known phases. Using this method, the arduous analysis and classification of hundreds of spectra is reduced to a much shorter analysis of only a few spectra.
- OPTICS; ATOMS AND MOLECULES; SPECTROSCOPY; PHOTON DETECTORS
78(2007); http://dx.doi.org/10.1063/1.2755391View Description Hide Description
We analyze sources of noise in kilohertz frequency pump/probe experiments and present a method for reducing experimental noise by identifying and filtering noisy shots. The power spectrum of instrumental noise shows high frequency, small amplitude modulations which cannot be averaged out. A histogram analysis shows that low frequency, large amplitude signals pose a serious obstacle to signal averaging for improved signal to noise. In kilohertz frequency pump/probe experiments, this low frequency noise typically arises from laser scatter due to bubbles, dust, and defects. We quantify the effectiveness in analyzing and rejecting these large amplitude signals which can produce a hindrance to the effectiveness of signal averaging.
78(2007); http://dx.doi.org/10.1063/1.2754444View Description Hide Description
We present a new technique to measure absolute total collision cross sections from metastable neon atoms. The technique is based on the observation of the decay rate of trapped atoms as they collide with room temperature atoms. We present the first measurement of this kind using trapped neon atoms in the metastable state colliding with thermal ground state argon. The measured cross section has a value of .