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Spatially offset Raman spectroscopy (SORS) offers the prospect of collecting spectral information detailing the molecular composition of biomaterials at greater depths below the surface layers than are normally probed by conventional Raman spectroscopy. By collecting off-axial scattered light, the technique overcomes the large background from in-line light within scattering media. In this paper we present a configuration which enables the highly efficient collection of spectral markers, indicative of bone health, including Raman signatures to assess phosphate, collagen and carbonate content, at millimeter depths. We demonstrate the effectiveness of the technique by performing spectral decompositions to analyze the molecular distribution of these markers non-invasively, using in vitro model systems, comprising bone and tissue, in situ.

The field of microfluidics promises new portable, low-cost sensing systems, as well as the capabilities to measure the physical or chemical properties of precious samples, for which only small volumes are available. However, when using microfluidic channels with millimeter to micron scale dimensions, together with optical sensing methods, these configurations result in short path lengths over which the signal can be acquired. Whilst polarimetry would greatly benefit from using small volumes, providing important information on the structure of chiral biomarkers in life sciences, the small interrogation volumes associated with the use of minute samples decreases the numbers of molecules in the light path that cause an optical rotation and reduces the sensitivity of the technique. Here, we show that when an optical beam, passing through a chiral sample, undergoes multiple reflections from suitably aligned external micromirrors, the usual cancelling out of the optical rotation, that occurs when the rotated polarized beam is passed back through a solution following reflection at a single mirror, can be negated. This enables the chirality of molecular species present in a microfluidic sample to be measured with increased sensitivity. This approach was validated experimentally using solutions of D-(+)-glucose as a model system, by investigating the effect of multiple reflections of a linearly polarized He-Ne laser beam and a 403 nm diode laser beam across the microfluidic channel. It was found that there was a 30-fold enhancement in the limit of detection with as few as 11 reflections through the sample.

It is well known that extracellular matrix stiffness can affect cell fate and change dynamically during many biological processes. Existing experimental means for in situ matrix stiffness modulation often alters its structure, which could induce additional undesirable effects on cells. Inspired by the phenomenon of depth sensing by cells, we introduce here core–shell microfibers with a thin collagen core for cell growth and an alginate shell that can be dynamically stiffened to deliver mechanical stimuli. This allows for the maintenance of biochemical properties and structure of the surrounding microenvironment, while dynamically modulating the effective modulus “felt” by cells. We show that simple addition of Sr2+ in media can easily increase the stiffness of initially Ca2+ cross-linked alginate shells. Thus, despite the low stiffness of collagen cores (

Optical-based microfluidic cell sorting has become increasingly attractive for applications in life and environmental sciences due to its ability of sophisticated cell handling in flow. The majority of these microfluidic cell sorting devices employ two-dimensional fluid flow control strategies, which lack the ability to manipulate the position of cells arbitrarily for precise optical detection, therefore resulting in reduced sorting accuracy and purity. Although three-dimensional (3D) hydrodynamic devices have better flow-focusing characteristics, most lack the flexibility to arbitrarily position the sample flow in each direction. Thus, there have been very few studies using 3D hydrodynamic flow focusing for sorting. Herein, we designed a 3D hydrodynamic focusing sorting platform based on independent sheath flow-focusing and pressure-actuated switching. This design offers many advantages in terms of reliable acquisition of weak Raman signals due to the ability to precisely control the speed and position of samples in 3D. With a proof-of-concept demonstration, we show this 3D hydrodynamic focusing-based sorting device has the potential to reach a high degree of accuracy for Raman activated sorting.

Raman activated cell sorting has emerged as a label-free technology that can link phenotypic function with genotypic properties of cells. However, its broad implementation is limited by challenges associated with throughput and the complexity of biological systems. Here, we describe a three-dimensional hydrodynamic focusing microfluidic system for a fully automated, continuous Raman activated cell sorting (3D-RACS). The system consists of a 3D printed detection chamber (1 mm3) that is integrated with a PDMS based sorting unit, optical sensors and an in-line collection module. It has the ability to precisely position cells in the detection chamber for Raman measurements, effectively eliminating spectroscopic interference from the device materials. This enables the sorting of a range of cell sizes (from 1 μm bacteria to 10's μm mammalian cells) with stable operation over >8 hours and high throughput. As a proof-of-concept demonstration, Raman-activated sorting of mixtures of Chlorella vulgaris and E. coli has demonstrated a purity level of 92.0% at a throughput of 310 cells per min. The platform employed in this demonstration features a simple “Raman window” detection system, enabling it to be built on a standard, inverted microscope. Together with its facile and robust operation, it provides a versatile tool for function-based flow cytometry and sorting applications in the fields of microbiology, biotechnology, life science and diagnostics.

We present a fully automated laser system with low-intensity noise for coherent Raman scattering microscopy. The robust two-color system is pumped by a solid-state oscillator, which provides Stokes pulses fixed at 1043 nm. The tunable pump pulses of 750 to 950 nm are generated by a frequency-doubled fiber-feedback femtosecond optical parametric oscillator. The resulting pulse duration of 1.2 ps provides a viable compromise between optimal coherent Raman scattering signal and the necessary spectral resolution. Thus a spectral range of 1015 to 3695 cm − 1 with spectral resolution of

The specific and multiplexed detection of DNA underpins many analytical methods, including the detection of microorganisms that are important in the medical, veterinary, and environmental sciences. To achieve such measurements generally requires enzyme-mediated amplification of the low concentrations of the target nucleic acid sequences present, together with the precise control of temperature, as well as the use of enzyme-compatible reagents. This inevitably leads to compromises between analytical performance and the complexity of the assay. The hybridization chain reaction (HCR) provides an attractive alternative, as a route to enzyme-free DNA amplification. To date, the linear nucleic acid products, produced during amplification, have not enabled the development of efficient multiplexing strategies, nor the use of label-free analysis. Here, we show that by designing new DNA nanoconstructs, we are able, for the first time, to increase the molecular dimensionality of HCR products, creating highly branched amplification products, which can be readily detected on label-free sensors. To show that this new, branching HCR system offers a route for enzyme-free, label-free DNA detection, we demonstrate the multiplexed detection of a target sequence (as the initiator) in whole blood. In the future, this technology will enable rapid point-of-care multiplexed clinical analysis or in-the-field environmental monitoring., DNA detection: enzyme-free amplification A hybridization chain reaction permits multiplexed and label-free DNA detection. Nucleic acid detection generally requires a suitable enzyme to amplify the typically low concentration of target nucleic acid sequences, as well as careful control of temperature. However, this limits the ability for multiplexing strategies. Now, a team led by Jonathan M. Cooper at University of Glasgow in the UK report the use of DNA nanoconstructs to enhance the molecular dimensionality of hybridization chain reaction (HCR) products, enabling label-free multiplexed detection; the use of a 3-arm DNA construct creates additional sites to initiate a chain reaction with high efficiency, removing the need for otherwise complex labeling approaches.

Spatially offset Raman spectroscopy is integrated with a fiber-coupled spatial heterodyne spectrometer to collect Raman spectra from deep within opaque or scattering materials. The method, named spatial heterodyne offset Raman spectroscopy generates a wavenumber-dependent spatial phase shift of the optical signal as a "spectral" image on a charge-coupled device detector. The image can be readily processed from the spatial domain using a single, simple, and "on-the-fly" Fourier transform to generate Raman spectra, in the frequency domain. By collecting all of the spatially offset Raman scattered photons that pass through the microscope's collection objective lens, the methodology gives an improvement in the Raman sensitivity by an order of magnitude. The instrumentation is both mechanically robust and "movement-free," which when coupled with the associated advantages of highly efficient signal collection and ease of data processing, enables rapid interfacial analysis of complex constructs based on established biomaterials models.

In creating mirrored silicon structures for micro-optics, the smoothness of the surface and etch rate are crucial parameters. We demonstrate a method of creating both 45° and 90° etch-planes from monocrystalline silicon for use as retro-reflective sidewalls in a microfluidic device. The technique uses the same photolithographic pattern orientation, but with two different etchants. Etching on direction in Si(100) with potassium hydroxide (KOH) gives vertical surfaces (where e.g. the high surface tension influences etching of crystallographic silicon planes), whilst tetramethylammonium hydroxide (TMAH) gives 45° sidewalls. We illustrate the use of these fabricated structures by creating arrays of micromirrors that enable an optical beam to be reflected parallel back and forth from 45° and −45° tilted vertical structures. This device has potential uses in optofluidic spectroscopic applications, where there is a need to increase the effective pathlength of a beam through a sample whilst keeping the device as small as possible.

Single cell Raman spectroscopy measures a spectral fingerprint of the biochemistry of cells, and provides a powerful method for label-free detection of living cells without the involvement of a chemical labelling strategy. However, as the intrinsic Raman signals of cells are inherently weak, there is a significant challenge in discriminating and isolating cells in a flowing stream. Here we report an integrated Raman-microfluidic system for continuous sorting of a stream of cyanobacteria, Synechocystis sp. PCC6803. These carotenoid-containing microorganisms provide an elegant model system enabling us to determine the sorting accuracy using the subtly different resonance Raman spectra of microorganism cultured in a (12)C or (13)C carbon source. Central to the implementation of continuous flow sorting is the use of "pressure dividers" that eliminate fluctuations in flow in the detection region. This has enabled us to stabilise the flow profile sufficiently to allow automated operation with synchronisation of Raman acquisition, real-time classification and sorting at flow rates of ca.

We report on the design and fabrication of a hybrid sensor that integrates transmission-mode localized surface plasmonic resonance (LSPR) into a quartz crystal microbalance (QCM) for studying biochemical surface reactions. The coupling of LSPR nanostructures and a QCM allows optical spectra and QCM resonant frequency shifts to be recorded simultaneously and analyzed in real time for a given surface adsorption process. This integration simplifies the conventional combination of SPR and QCM and has the potential to be miniaturized for application in point-of-care (POC) diagnostics. The influence of antibody-antigen recognition effect on both the QCM and LSPR has been analyzed and discussed.

A new approach is described herein, where neutron reflectivity measurements that probe changes in the density profile of thin films as they absorb material from the gas phase have been combined with a Love wave based gravimetric assay that measures the mass of absorbed material. This combination of techniques not only determines the spatial distribution of absorbed molecules, but also reveals the amount of void space within the thin film (a quantity that can be difficult to assess using neutron reflectivity measurements alone). The uptake of organic solvent vapours into spun cast films of polystyrene has been used as a model system with a view to this method having the potential for extension to the study of other systems. These could include, for example, humidity sensors, hydrogel swelling, biomolecule adsorption or transformations of electroactive and chemically reactive thin films. This is the first ever demonstration of combined neutron reflectivity and Love wave-based gravimetry and the experimental caveats, limitations and scope of the method are explored and discussed in detail.

An artificial olfactory system (or “electronic nose”) has been developed to investigate the interactions between polymer-modified sensors with odorant vapors from the headspace of primary alcohol samples. Complementary pairs of polymer-coated quartz crystal microbalance sensors and polymer/carbon black-coated micro-resistance sensors have been used to produce a characteristic value for the odorants (Sfr), related to the odorant molecular density, which can be used in electronic nose applications for odor discrimination. An application-specific integrated circuit (ASIC) is also described which controls and collects data from the quartz crystal microbalance-based sensors, enabling the future development of a hand-held/miniaturized detection system utilizing these types of sensor.

This paper describes studies of a combined electrochemical/acoustic wave sensor for detection of metal ions in aqueous solutions. The sensor is based upon surface complexation of the metal ions at thiodisuccinic acid (TDS) functionalised self-assembled monolayer (SAM) modified electrodes on 10 MHz AT-cut quartz resonators, functioning as a quartz crystal microbalance (QCM). The SAM-modified electrodes were employed for the detection of Cd(II) ions in single and mixed metal ion solutions, with Pb(II) or Cu(II) as the interferants. Acoustic determination was based on the QCM frequency change associated with the binding to the surface-immobilised ligand of metal ions as a function of their concentration. Frequency response data were acquired under emersed and immersed conditions for ligand binding to the Au electrode and, subsequently, metal ion binding to the ligand. In the latter case, the data were interpreted according to a range of isotherms, of which the Temkin isotherm was found empirically best to describe the concentration dependence. The acoustic wave data yielded information on equilibrium binding stoichiometry and energetics. The extent of metal ion binding was also determined by coulometric assay (upon reduction to the zero-valent metal) after transfer to metal ion-free electrolyte solution. XPS studies of surface-bound metal-TDS ligand complexes confirmed the binding stoichiometry obtained from the electrochemical and acoustic wave responses, and provided information on the ligand–substrate binding and bound analyte oxidation state.

Background In cancer cells in vitro, the glycolytic pathway and the mitochondrial tricarboxylic acid (TCA) cycle are programmed to produce more precursor molecules, and relatively less ATP, than in differentiated cells. We address the questions of whether and where these changes occur in vivo in glioblastomas grown from C6 cells in rat brain. These gliomas show some spatial organization, notably in the upregulation of membrane proton transporters near the rim. Results We immunolabeled pairs of proteins (as well as DNA) on sections of rat brains containing gliomas, measured the profiles of fluorescence intensity on strips 200 µm wide and at least 3 mm long running perpendicular to the tumor rim, and expressed the intensity in the glioma relative to that outside. On averaged profiles, labeling of a marker of the glycolytic pathway, glyceraldehyde 3-phosphate dehydrogenase (GAPDH), was, as expected, greater in the glioma. Over distances up to 2.5 mm into the glioma, expression of a marker of the TCA cycle, Tom20, a pre-protein receptor on the translocation complex of the mitochondrial outer membrane, was also upregulated. The ratio of upregulation of Tom20 to upregulation of GAPDH was, on average, slightly greater than one. Near the rim (0.4–0.8 mm), GAPDH was expressed less and there was a peak in the mean ratio of 1.16, SEM = 0.001, N = 16 pairs of profiles. An antibody to V-ATPase, which, by pumping protons into vacuoles contributes to cell growth, also indicated upregulation by about 40%. When compared directly with GAPDH, upregulation of V-ATPase was only 0.764, SD = 0.016 of GAPDH upregulation. Conclusions Although there was considerable variation between individual measured profiles, on average, markers of the glycolytic pathway, of mitochondria, and of cell proliferation showed coherent upregulation in C6 gliomas. There is a zone, close to the rim, where mitochondrial presence is upregulated more than the glycolytic pathway, in agreement with earlier suggestions that lactate is taken up by cells near the rim. Electronic supplementary material The online version of this article (doi:10.1186/s13104-015-1191-z) contains supplementary material, which is available to authorized users.

This paper describes the development and evaluation of a custom-built impedance analyzer, which uses a multiplexing bridge circuit to characterize an array of polymer-coated quartz crystal microbalance (QCM) sensors. The analyzer is constructed on a single printed circuit board with minimum components and is sufficiently compact for integration into a handheld format. The custom-built device is used to observe the changes that occur in QCM sensors when experimental conditions such as polymer coating film thickness, odorant vapor pressure, and relative molecular mass are varied. An equivalent electric circuit for a QCM is used to model the conductance and susceptance data captured by the analyzer. The measured response of an array of QCM sensors demonstrates that the custom-built device is a suitable instrument for detecting different gases and understanding polymer–vapor interactions.

We describe the development of an integrated lensed Arrayed Waveguide Grating (AWG) microspectrometer for localized multiplexing fluorescence measurements. The device, which has a footprint that is only 1 mm wide and 1 cm long, is capable of spectroscopic measurements on chip. Multiple fluorescence signals were measured simultaneously based upon simple intensity readouts from a CCD camera. We also demonstrate the integration of the AWG spectrometer with a microfluidic platform using a lensing function to confine the beam shape for focused illumination. This capability enhances signal collection, gives better spatial resolution, and provides a route for the analysis of small volume samples (e.g. cells) in flow. To show these capabilities we developed a novel "bead-AWG" platform with which we demonstrate localized multiplexed fluorescence detection either simultaneously or successively. Such an integrated system provides the basis for a portable system capable of optical detection of multi-wavelength fluorescence from a single defined location.

We present a straightforward method for measuring the relative viscosity of fluids via a simple graphical analysis of the normalised position autocorrelation function of an optically trapped bead, without the need of embarking on laborious calculations. The advantages of the proposed microrheology method are evident when it is adopted for measurements of materials whose availability is limited, such as those involved in biological studies. The method has been validated by direct comparison with conventional bulk rheology methods and has been applied both to characterise synthetic linear polyelectrolytes solutions and to study biomedical samples.

Dedifferentiation of chondrocytes during in vitro expansion remains an unsolved challenge for repairing serious articular cartilage defects. In this study, a novel culture system was developed to modulate single cell geometry in 3D and investigate its effects on the chondrocyte phenotype. The approach uses 2D micropatterns followed by in situ hydrogel formation to constrain single cell shape and spreading. This enables independent control of cell geometry and extracellular matrix. Using collagen I matrix, we demonstrated the formation of a biomimetic collagenous “basket” enveloping individual chondrocytes cells. By quantitatively monitoring the production by single cells of chondrogenic matrix (e.g. collagen II and aggrecan) during 21-day cultures, we found that if the cell’s volume decreases, then so does its cell resistance to dedifferentiation (even if the cells remain spherical). Conversely, if the volume of spherical cells remains constant (after an initial decrease), then not only do the cells retain their differentiated status, but previously de-differentiated redifferentiate and regain a chondrocyte phenotype. The approach described here can be readily applied to pluripotent cells, offering a versatile platform in the search for niches toward either self-renewal or targeted differentiation.

Cell proliferation and migration are fundamental processes in determining cell and tissue behaviour. In this study we show the design and fabrication of a new single cell microfluidic structure, called a “vertically integrated array” or “VIA” trap to explore quantitative functional assays including single cell attachment, proliferation and migration studies. The chip can be used in a continuous (flow-through) manner, with a continuous supply of new media, as well as in a quiescent mode. We show the fabrication of the device, together with the flow characteristics inside the network of channels and the single cell traps. The flow patterns inside the device not only facilitate cell trapping, but also protect the cells from mechanical flow-induced stress. MDA-MB-231 human breast cancer cells were used to study attachment and detachment during the cell cycle as well as explore the influences of the chemokine SDF-1 (enabling the quantification of the role of chemokine gradients both on pseudopod formation and directional cell migration).

Bacteria persistence is a well-known phenomenon, where a small fraction of cells in an isogenic population are able to survive high doses of antibiotic treatment. Since the persistence is often associated with single cell behaviour, the ability to study the dynamic response of individual cells to antibiotics is critical. In this work, we developed a gradient microfluidic system that enables long-term tracking of single cell morphology under a wide range of inhibitor concentrations. From time-lapse images, we calculated bacterial growth rates based on the variations in cell mass and in cell number. Using E. coli and Comamonas denitrificans to amoxicillin inhibition as model systems, we found the IC50 determined via both methods are in a good agreement. Importantly, the growth rates together with morphological dynamics of individual cells has led to the discovery of a new form of persistence to amoxicillin. Normal cells that are sensitive to amoxicillin gain persistence or recover from the killing process, if they have had an opportunity to utilise the cytoplasm released from lysed cells close-by. We term this acquired persistence in normal growing cells “opportunistic persistence”. This finding might shed new insights into biofilm resistance and the effect of antibiotics on environmental microbes.

Previously there has been considerable research in producing biosensors by the entrapment of proteins in electrochemically formed conducting polymer films. In this paper we describe a method enabling the amount of the enzyme glucose oxidase, entrapped at the surface of a poly(pyrrole) film to be quantified using X-ray photoelectron spectroscopy (XPS). Components of the biosensor XPS spectrum were deconvoluted as a linear combination of characteristic polymer and enzyme spectra, using primarily the high-energy C(1s) signals (288.2 and 286.4 eV) due to functional groups in the enzyme and the N(1s) signal present in both enzyme and polymer samples at 400.2 eV, together with the lesser shoulder at 398.0 eV, related to iminic nitrogen species in the polymer alone. The O(1s) peak at 531.7 eV, associated with the immobilized enzyme, provided additional compositional information, although here the effects of surface contamination were more pronounced. Further, and in parallel with this XPS study, corroborative re...

We present a simple and non-invasive experimental procedure to measure the linear viscoelastic properties of cells by passive particle tracking microrheology. In order to do this, a generalised Langevin equation is adopted to relate the timedependent thermal fluctuations of a probe sensor, immobilised to the cell’s membrane, to the frequency-dependent viscoelastic moduli of the cell. The method has been validated by measuring the linear viscoelastic response of a soft solid and then applied to cell physiology studies. It is shown that the viscoelastic moduli are related to the cell’s cytoskeletal structure, which in this work is modulated either by inhibiting the actin/myosin-II interactions by means of blebbistatin or by varying the solution osmolarity from iso- to hypo-osmotic conditions. The insights gained from this form of rheological analysis promises to be a valuable addition to physiological studies; e.g. cell physiology during pathology and pharmacological response.

We demonstrate a polymer resonator microfluidic biosensor that overcomes the complex manufacturing procedures required to fabricate traditional devices. In this new format, we show that a gapless light coupling photonic configuration, fabricated in SU8 polymer, can achieve high sensitivity, label-free chemical sensing in solution and high sensitivity biological sensing, at visible wavelengths.

We demonstrate a single-step method for the generation of collagen and poly-l-Lysine (PLL) micropatterns on a poly(ethylene glycol) (PEG) functionalized glass surface for cell based assays. The method involves establishing a reliable silanization method to create an effective non-adhesive PEG layer on glass that inhibits cell attachment, followed by the spotting of collagen or PLL solutions using non-contact piezoelectric printing. We show for the first time that the spotted protein micropatterns remain stable on the PEG surface even after extensive washing, thus significantly simplifying protein pattern formation. We found that adherence and spreading of NIH-3T3 fibroblasts was confined to PLL and collagen areas of the micropatterns. In contrast, primary rat hepatocytes adhered and spread only on collagen micropatterns, where they formed uniform, well defined functionally active cell arrays. The differing affinity of hepatocytes and NIH-3T3 fibroblasts for collagen and PLL patterns was used to develop a simple technique for creating a co-culture of the two cell types. This has the potential to form structured arrays that mimic the in vivo hepatic environment and is easily integrated within a miniaturized analytical platform for developing high throughput toxicity analysis in vitro.

A combination of XPS, reflectance infrared spectroscopy, and neutron reflectivity measurements has been used to probe the spatial and global extents to which carboxylic acid motifs in electrodeposited conducting polymer films can be functionalized by reaction with vapor phase reagents (a carbodiimide together with trifluoroethanol) with the goal of controlling hydrophobicity. Across a range of polymer deposition and reaction temperatures, neutron reflectivity showed that, surprisingly, functionalization of the polymer matrix at depths >5-10 nm into the polymer film was always significantly lower than at the exposed surface. The most efficient functionalization was found to occur when a low-density polymer matrix was prepared by elution of motifs cleaved from the polymer by base hydrolysis. Finally, when trifluoroethanol functionalization was performed, the macroscopic property of hydrophobicity was related to the surface, internal microstructure, and composition of the reacted films as elucidated by the above combination of probes.

We describe in situ neutron reflectivity (NR) and RAIRS studies of the chemical modification of films of a polypyrrole-based conducting polymer derived from the pentafluorophenyl ester of poly(pyrrole-N-propanoic acid) (PFP) electrodeposited on electrode surfaces. We explore the role of the solvent in controlling the rate of reaction with solution-based nucleophiles (amines, which react with the ester to form amides). By varying the identity of the solvent (water vs acetonitrile) and the neutron contrast (deuteration), we find that both the identity of the solvent and its population within the film are paramount in determining chemical reactivity and electroactivity. IR signatures allow monitoring of the reaction of solution-based amine-tagged species such as amino-terminated poly(propylene glycol), ferrocene ethylamine, and lysine with film-based ester functionalities: the carbonyl bands show ester/amide interconversion and some hydrolysis to acid. Time-dependent spectral analysis shows marked variations in reaction rate with (i) (co-)polymer composition (replacement of some fluorinated ester-functionalized pyrrole with unfunctionalized pyrrole), (ii) the solvent to which the polymer film is exposed, and (iii) the rate of polymer deposition. NR data provide solvent profiles as a function of distance perpendicular to the interface, the variations of which provide an explanation for film reactivity patterns. Homopolymer films are relatively hydrophobic, thus hindering reaction with species present in water solutions. Incorporating pyrrole groups raises the solvent population-dramatically for water-thereby facilitating entry and reaction of aqueous-based lysine. Changing film deposition rate yields films with different absolute levels of solvent and reactivity patterns that are dependent on the size of the reactant molecules: more rapid deposition of polymer gives films with a more open structure leading to a higher solvent content and thence increased reactivity. These results, supported by XPS and AFM data, allow assembly of composition-structure-reactivity correlations, in which the controlling feature is film solvation.

An all-digital interface, application specific integrated circuit (ASIC) has been developed for the control and data sampling of a quartz crystal microbalance (QCM)-based electronic nose. The ASIC is capable of measuring QCM resonant frequency between 0 and 11 MHz with a resolution of 1 Hz and ±1 Hz precision. The ASIC has been used to obtain measurements from polymer coated QCM sensors, in conjunction with polymer/carbon-black coated micro-resistance (μR) sensors, in the detection of primary alcohols. A full system-on-a-chip (SoC) electronic nose, currently under test, which supports arrays of eight QCM and eight μR sensors along with on-chip processing capability, is also described. © 2004 Elsevier B.V. All rights reserved.

Latent fingerprints on metal surfaces may be visualized by exploiting the insulating characteristics of the fingerprint deposit as a “mask” to direct electrodeposition of an electroactive polymer to the bare metal between the fingerprint ridges. This approach is complementary to most latent fingerprint enhancement methods, which involve physical or chemical interaction with the fingerprint residue. It has the advantages of sensitivity (a nanoscale residue can block electron transfer) and, using a suitable polymer, optimization of visual contrast. This study extends the concept in two significant respects. First, it explores the feasibility of combining observation based on optical absorption with observation based on fluorescence. Second, it extends the methodology to materials (here, polypyrrole) that may undergo post-deposition substitution chemistry, here binding of a fluorophore whose size and geometry preclude direct polymerization of the functionalised monomer. The scenario involves a lateral spatial image (the whole fingerprint, first level detail) at the centimetre scale, with identification features (minutiae, second level detail) at the 100–200 μm scale and finer features (third level detail) at the 10–50 μm scale. However, the strategy used requires vertical spatial control of the (electro)chemistry at the 10–100 nm scale. We show that this can be accomplished by polymerization of pyrrole functionalised with a good leaving group, ester-bound FMOC, which can be hydrolysed and eluted from the deposited polymer to generate solvent “voids”. Overall the “void” volume and the resulting effect on polymer dynamics facilitate entry and amide bonding of Dylight 649 NHS ester, a large fluorophore. FTIR spectra demonstrate the spatially integrated compositional changes. Both the hydrolysis and fluorophore functionalization were followed using neutron reflectivity to determine vertical spatial composition variations, which control image development in the lateral direction.

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Here we have studied the electrocopolymerisation of binary mixtures of functionalised thiophenes in varying compositions and determined independently for each copolymer the spectroelectrochemical responses and the composition of the material using X-ray photoelectron spectroscopy. We have observed strong correlations between the composition of the copolymer material and the composition of the binary solution from which the polymer was grown. In addition, we have shown that the spectroelectrochemical properties of the copolymers indicate the presence of random copolymer material where the lambda(Max) values of the neutral, undoped, polymer scales with composition but also suggest that there may be small amounts of block copolymer or phase-separated mixtures of the homopolymer components.

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We have studied the anodic dissolution (electropolishing) of various stainless steel alloys in an ionic liquid comprising a 2 : 1 stoichiometric mix of ethylene glycol (EG) and choline chloride. We have used a combination of electrochemical and spectroscopic methods together with in situ liquid probe microscopy. We discuss the role and influence of the surface oxide passivation layer, characterized here by X-ray photoelectron spectroscopy (XPS) and linear sweep voltammetry, on the polishing process. We address the question of dealloying during the polish in order to contribute to our understanding of the viability of the ionic liquid as a replacement industrial electropolishing medium; the current commercial process uses a corrosive mixture of phosphoric and sulfuric acids. Also, we present data from ex situ and in situ liquid AFM studies giving both a qualitative and quantitative insight into the nature and scale of morphological changes at the steel surface during the polishing process.

Surface engineering provides a powerful tool to create model systems to investigate the complex interactions between cells and the extracellular matrix (ECM). Cell adhesive peptide ligands (e.g. Arginine-Glycine-Aspatate (RGD) sequence) and carbohydrates are abundant in the ECM, and both are involved in mediating cell adhesion. However, how these interact is not well understood in vivo. Model systems to investigate their collective roles are rare. We have developed a robust surface patterning method allowing spatial control of carbohydrate (i.e. mannose) and RGD on glass while overcoming non-specific biomolecular interactions. The method effectively combines a traditional photolithographic process with two robust chemical pathways, namely click chemistry and silanization, in order to tailor the surface chemistry. This method is especially promising for the quantitative immobilization of different molecules and holds potential for the investigation of interactions between carbohydrates and common ECM proteins on cell adhesion. - See more at: http://www.eurekaselect.com/105477/article#sthash.LKEggb6P.dpuf