Dynamic behaviour of ISFET-based sensor-actuator systems

Rapid acid-base titrations can be performed at the surface of a noble-metal electrode with coulometrically generated ions. An ISFET is used as an indicator electrode to detect the equivalence point in the resulting titration curve. The time needed to reach the equivalence point is typically 0.5 to 10 s for acid/base concentrations ranging from 0.5 × 10−3 to 20 × 10−3 mol l−1.\ud \ud A model is presented describing the concentration profiles which appear during the coulometric generation of ions. The result of this model is in good agreement with corresponding measurements. These measurements are carried out with two different actuator electrodes, of which the processing steps are described

High-throughput on-chip DNA fragmentation

free microfluidic deoxyribonucleic acid (DNA) fragmentation chip that is based on hydrodynamic shearing. Genomic DNA has been reproducibly fragmented with 2-10 kbp fragment lengths by applying hydraulic pressure ΔP across micromachined constrictions in the microfluidic channels. The utilization of a series of constrictions reduces the variance of the fragmented DNA length distribution; and parallel microfluidic channels design eliminates the device clogging

Ultra-rapid and relative humidity independent drying of nanochannels

We observed that water-filled nanochannels dried up to 1000 times faster than predicted by vapor diffusional drying. Here we show that this ultra-rapid water transport is caused by very sharp channel corners siphoning (wicking) the water to the channel exit before it evaporates. Evidence is also provided that these sharp corners make the drying process independent of the relative humidity (RH) of the environment up to an RH of more than 0.9. To our knowledge this is the first time that nanochannel drying has been observed, and both the acceleration of drying and the independence of RH are highly surprising

Droplet microreactor for reaction monitoring at elevated temperatures and pressure

Recording reaction kinetics in detail and at various reaction conditions can be a time-consuming process. Microdroplets form ideal reaction chambers, suitable for high-throughput studies [1]. We report the fabrication of a microfluidic droplet-based microreactor operating at elevated temperatures (up to 130 °C) and pressures (up to 0.7 MPa), to rapidly study reaction kinetics. As proof-of-principle, the temperature-dependent fluorescence of Rhodamine B in ethanol is monitored [2]. Time-resolved information is obtained by measuring at multiple spots in the microreacto

Wafer-scale fabrication of high-quality tunable gold nanogap arrays for surface-enhanced Raman scattering

We report a robust and high-yield fabrication method for wafer-scale patterning of high-quality arrays of dense gold nanogaps, combining displacement Talbot lithography based shrink-etching with dry etching, wet etching, and thin film deposition techniques. By using the self-sharpening of -oriented silicon crystal planes during the wet etching process, silicon structures with extremely smooth nanogaps are obtained. Subsequent conformal deposition of a silicon nitride layer and a gold layer results in dense arrays of narrow gold nanogaps. Using this method, we successfully fabricate high-quality Au nanogaps down to 10 nm over full wafer areas. Moreover, the gap spacing can be tuned by changing the thickness of deposited Au layers. Since the roughness of the template is minimized by the crystallographic etching of silicon, the roughness of the gold nanogaps depends almost exclusively on the roughness of the sputtered gold layers. Additionally, our fabricated Au nanogaps show a significant enhancement of surface-enhanced Raman scattering (SERS) signals of benzenethiol molecules chemisorbed on the structure surface, at an average enhancement factor up to 1.5 x 10(6)

Serum fatty acid chain length associates with prevalent symptomatic end-stage osteoarthritis, independent of BMI

Higher body mass index (BMI) is associated with osteoarthritis (OA) in both weight-bearing and non-weight-bearing joints, suggesting a link between OA and poor metabolic health beyond mechanical loading. This risk may be influenced by systemic factors accompanying BMI. Fluctuations in concentrations of metabolites may mark or even contribute to development of OA. This study explores the association of metabolites with radiographic knee/hip OA prevalence and progression. A 1H-NMR-metabolomics assay was performed on plasma samples of 1564 cases for prevalent OA and 2,125 controls collected from the Rotterdam Study, CHECK, GARP/NORREF and LUMC-arthroplasty cohorts. OA prevalence and 5 to 10 year progression was assessed by means of Kellgren-Lawrence (KL) score and the OARSI-atlas. End-stage knee/hip OA (TJA) was defined as indication for arthroplasty surgery. Controls did not have OA at baseline or follow-up. Principal component analysis of 227 metabolites demonstrated 23 factors, of which 19 remained interpretable after quality-control. Associations of factor scores with OA definitions were investigated with logistic regression. Fatty acids chain length (FALen), which was included in two factors which associated with TJA, was individually associated with both overall OA as well as TJA. Increased Fatty Acid chain Length is associated with OA

Load to capacitance transfer using different spring elements in capacitive transducers

Many physical sensors in which a displacement is the result of a change in the variable to be measured rely on the principle of capacitive transduction to transfer this displacement into a suitable electric signal. Commonly, the linearity of this transduction is one of the design criteria. The total transduction of physical load to capacitance change can be subdivided into the transfer from load to displacement and from displacement to capacitance change. The latter is non-linear due to its well-known hyperbolic behaviour. The first one — that of load to displacement — depends on the nature of the spring elements between the two plates of the capacitor. When, e.g., a rubber elastic spring is applied, the load to displacement transfer is also not linear. It is the aim of this paper to show that the two non-linear transfer functions of the mentioned subsystems result into a remarkably increased linearity for the transfer of the total capacitive transducer. The thus obtained theoretical relation is experimentally verified for the most favourable situation, using rubber elastic springs. The results are in good agreement with the theory