This paper describes a procedure that makes it possible to design and fabricate (including sealing) microfluidic systems in an elastomeric materialpoly(dimethylsiloxane) (PDMS)in less than 24 h. A network of microfluidic channels (with width >20 μm) is designed in a CAD program. This design is converted into a transparency by a high-resolution printer; this transparency is used as a mask in photolithography to create a master in positive relief photoresist. PDMS cast against the master yields a polymeric replica containing a network of channels. The surface of this replica, and that of a flat slab of PDMS, are oxidized in an oxygen plasma. These oxidized surfaces seal tightly and irreversibly when brought into conformal contact. Oxidized PDMS also seals irreversibly to other materials used in microfluidic systems, such as glass, silicon, silicon oxide, and oxidized polystyrene; a number of substrates for devices are, therefore, practical options. Oxidation of the PDMS has the additional advantage that it ...

Rapid prototyping of microfluidic systems in poly(dimethylsiloxane)

Hydrophilic polymers are the center of research emphasis in nanotechnology because of their perceived “intelligence”. They can be used as thin films, scaffolds, or nanoparticles in a wide range of biomedical and biological applications. Here we highlight recent developments in engineering uncrosslinked and crosslinked hydrophilic polymers for these applications. Natural, biohybrid, and synthetic hydrophilic polymers and hydrogels are analyzed and their thermodynamic responses are discussed. In addition, examples of the use of hydrogels for various therapeutic applications are given. We show how such systems’ intelligent behavior can be used in sensors, microarrays, and imaging. Finally, we outline challenges for the future in integrating hydrogels into biomedical applications.

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Hydrogels in Biology and Medicine: From Molecular Principles to Bionanotechnology†

When considering new sensory technologies one should look to nature for guidance. Indeed, living organisms have developed the ultimate chemical sensors. Many insects can detect chemical signals with perfect specificity and incredible sensitivity. Mammalian olfaction is based on an array of less discriminating sensors and a memorized response pattern to identify a unique odor. It is important to recognize that the extraordinary sensory performance of biological systems does not originate from a single element. In actuality, their performance is derived from a completely interactive system wherein the receptor is served by analyte delivery and removal mechanisms, selectivity is derived from receptors, and sensitivity is the result of analyte-triggered biochemical cascades. Clearly, optimal artificial sensory sys-

Conjugated polymer-based chemical sensors.

Wearable sensor technologies are essential to the realization of personalized medicine through continuously monitoring an individual's state of health. Sampling human sweat, which is rich in physiological information, could enable non-invasive monitoring. Previously reported sweat-based and other non-invasive biosensors either can only monitor a single analyte at a time or lack on-site signal processing circuitry and sensor calibration mechanisms for accurate analysis of the physiological state. Given the complexity of sweat secretion, simultaneous and multiplexed screening of target biomarkers is critical and requires full system integration to ensure the accuracy of measurements. Here we present a mechanically flexible and fully integrated (that is, no external analysis is needed) sensor array for multiplexed in situ perspiration analysis, which simultaneously and selectively measures sweat metabolites (such as glucose and lactate) and electrolytes (such as sodium and potassium ions), as well as the skin temperature (to calibrate the response of the sensors). Our work bridges the technological gap between signal transduction, conditioning (amplification and filtering), processing and wireless transmission in wearable biosensors by merging plastic-based sensors that interface with the skin with silicon integrated circuits consolidated on a flexible circuit board for complex signal processing. This application could not have been realized using either of these technologies alone owing to their respective inherent limitations. The wearable system is used to measure the detailed sweat profile of human subjects engaged in prolonged indoor and outdoor physical activities, and to make a real-time assessment of the physiological state of the subjects. This platform enables a wide range of personalized diagnostic and physiological monitoring applications.

/pdf/fully-integrated-wearable-sensor-arrays-for-multiplexed-in-4nphg673vl.pdf

Fully integrated wearable sensor arrays for multiplexed in situ perspiration analysis

AACR Centennial Conference: Translational Cancer Medicine-- Nov 4-8, 2007; Singapore

PL02-05 

All cancers are due to abnormalities in DNA. The availability of the human genome sequence has led to the proposal that resequencing of cancer genomes will reveal the full complement of somatic mutations and hence all the cancer genes. To explore the nature of the information that will be derived from cancer genome sequencing we have sequenced the coding exons of the family of 518 protein kinases, ~1.3Mb DNA per cancer sample, in 210 cancers of diverse histological types. Despite the screen being directed toward the coding regions of a gene family that has previously been strongly implicated in oncogenesis, the results indicate that the majority of somatic mutations detected are “passengers”. There is considerable variation in the number and pattern of these mutations between individual cancers, indicating substantial diversity of processes of molecular evolution between cancers. The imprints of exogenous mutagenic exposures, mutagenic treatment regimes and DNA repair defects can all be seen in the distinctive mutational signatures of individual cancers. This systematic mutation screen and others have previously yielded a number of cancer genes that are frequently mutated in one or more cancer types and which are now anticancer drug targets (for example BRAF , PIK3CA , and EGFR ). However, detailed analyses of the data from our screen additionally suggest that there exist a large number of additional “driver” mutations which are distributed across a substantial number of genes. It therefore appears that cells may be able to utilise mutations in a large repertoire of potential cancer genes to acquire the neoplastic phenotype. However, many of these genes are employed only infrequently. These findings may have implications for future anticancer drug development.

Patterns of Somatic Mutation in Human Cancer Genomes

Polymer with pendant methacryloyl group was synthesized by the substitution reaction of poly(2-hydroxyethyl methacrylate) [poly(HEMA)] with methacryloyl chloride. This photocurable polymer was characterized using 1H-NMR and bromine titration, and the results were reasonably well consistent. The photocrosslinking of this modified poly(HEMA) was carried out by the addition of a low molecular weight sensitizer without adding functional monomer and crosslinker. These precursors showed a high photosensitivity. Polymers with a degree of substitution as low as 2 mol-% methacryloyl group could be efficiently crosslinked within few seconds of UV exposure to give water insoluble transparent hydrogel membranes. By irradiation of a film of the photocurable polymer precursor containing lacatate oxidase (LOD), a rather unstable enzyme, the enzyme was gently immobilized by physical entrapment.

Photolithographically patternable modified poly(HEMA) hydrogel membrane

Nanoparticle exsolution is regarded as a promising alternative to classical catalyst synthesis routes. In this work, we compare the catalytic performance of nanoparticles formed by in-situ exsolution during dry reforming of methane with particles pre-formed by reductive pre-treatment. The experiments were conducted on three perovskite-type oxides. Using a combination of in-situ and operando spectroscopic investigations (x-ray diffraction, near ambient pressure x-ray photoelectron spectroscopy) and the correlation to the obtained catalytic results, we could highlight that pre-formed nanoparticles strongly enhance the activity compared to in-situ exsolution. Scanning electron microscope images recorded after catalytic tests revealed that nanoparticles formed during reductive pre-treatment are bigger on average than particles formed in-situ . Furthermore, B-site doping with Co or Ni significantly enhanced the catalytic activity. Importantly, the perovskite host lattice was stable in all experiments, thus providing the necessary enhanced oxygen surface chemistry which is the key to the coking resistance of the investigated materials. Additionally, we observe a temperature dependent change of mechanism leading to different product ratios. • Perovskite catalysts with different B-site doping used for dry reforming of methane. • Operando XRD and in-situ NAP-XPS measurements during reaction. • Comparison of differently triggered exsolution: in-situ and pre-reduction. • Bigger nanoparticles lead to better yield during dry reforming of methane. • No formation of carbon nanotubes was observed – enhanced coking resistance. 

Impact of nanoparticle exsolution on dry reforming of methane: Improving catalytic activity by reductive pre-treatment of perovskite-type catalysts

Room Temperature CO Sensing with Metal Oxide Nanoparticles Using work Function Readout

Porous (Zr0.5,Sr0.5)TiO3 and MgO (1, 3, 5 mol%) doped ZST nanocomposites have been developed and investigated as humidity sensing elements. The surface area analyser and FESEM data have indicated that the MgO doped perovskites are contained of the macropores and grain size of about 77 to 87 nm. EFTEM proved the reduction of particle size by addition of MgO dopant concentration. While pure ZST shows BET surface area of about 58 m2/g, MgO doped samples exhibit about 12 m2/g. Sensor contained of ZST doped with 3 mol% MgO shows highest sensitivity with about four orders of magnitude change in impedance within the range of 20% to 95% RH.

https://www.mdpi.com/2504-3900/1/4/408/pdf

MgO-Doped (Zr,Sr)TiO3 Perovskite Humidity Sensors: Microstructural Effects on Water Permeation

The medical sensor system (10) comprises a sensor (14), a characteristic carrier (16) and a characteristic carrier receptor (18). The sensor is arranged in vivo for detection of the characteristic (12). The sensor comprises a semiconductor component (22), and an area (24) of the sensor is laminated with the characteristic carrier receptor. An independent claim is also included for a method for operating a medical sensor system for detecting a characteristic of an animal or human body.

Gerald Urban

Papers

Photolithographically patternable modified poly(HEMA) hydrogel membrane

Impact of nanoparticle exsolution on dry reforming of methane: Improving catalytic activity by reductive pre-treatment of perovskite-type catalysts

Room Temperature CO Sensing with Metal Oxide Nanoparticles Using work Function Readout

MgO-Doped (Zr,Sr)TiO3 Perovskite Humidity Sensors: Microstructural Effects on Water Permeation

Medical sensor system