Compliance of a microstructured, soft sampling device for transcutaneous blood gas monitoring.

Premature neonates are too small for repeated blood sampling, but still require precise monitoring of blood gas levels. The standard method therefore involves transcutaneous blood gas monitoring (TBM), i.e. analyzing gas that permeates the skin. The method involves skin heating and requires frequent relocation of a rigid sensor that is adhesively mounted to the skin, which makes the monitoring intermittent and can cause tissue damage. To mitigate this, this paper introduces a TBM concept that replaces the sensor with a small, non-adhesive, flexible, polydimethylsiloxane patch, routing the gases through skin-facing microchannels laid out in various configurations, to an external optical emission spectroscopy system (OES). As the OES depends on a constant flow of gas, we have investigated the effects external loads, both vertical and with a transverse component, have on the aerodynamic resistance of the patches. The experiments show that patches with 200 µm wide channels can withstand uniformly distributed forces up to 25 N with a change in aerodynamic resistance of about 0.01 mbar per sccm per newton. In subsequent measurements, the proof of concept (POC) TBM system showed a strong and fast blood gas signal that was unaffected by all likely loads in the intended application. Moreover, the rise time of the signal is shown to be inversely proportional to the aerodynamic resistance, and the signal strength to be proportional to the skin area exposed to the microchannels. With these results, the POC TBM system is a viable first step towards truly continuous blood gas monitoring of prematurely born children.

Acoustically enriching, large-depth aquatic sampler.

In marine biology, it is useful to collect water samples when exploring the distribution and diversity of microbial communities in underwater environments. In order to provide, e.g., a miniaturized submersible explorer with the capability of collecting microorganisms, a compact sample enrichment system has been developed. The sampler is 30 mm long, 15 mm wide, and just a few millimetres thick. Integrated in a multilayer steel, polyimide and glass construction is a microfluidic channel with piezoelectric transducers, where microorganism and particle samples are collected and enriched, using acoustic radiation forces for gentle and labelless trapping. High-pressure, latchable valves, using paraffin as the actuation material, at each end of the microfluidic channel keep the collected sample pristine. A funnel structure raised above the surface of the device directs water into the microfluidic channel as the vehicle propels itself or when there is a flow across its hull. The valves proved leak proof to a pressure of 2.1 MPa for 19 hours and momentary pressures of 12.5 MPa, corresponding to an ocean depth of more than 1200 metres. By reactivating the latching mechanism, small leakages through the valves could be remedied, which could thus increase the leak-less operational time. Fluorescent particles, 1.9 µm in diameter, were successfully trapped in the microfluidic channel at flow rates up to 15 µl min(-1), corresponding to an 18.5 cm s(-1) external flow rate of the sampler. In addition, liquid-suspended GFP-marked yeast cells were successfully trapped.

Simulation, manufacturing, and evaluation of a sonar for a miniaturized submersible explorer.

Single-beam side-scan sonar elements, to be fitted on a miniaturized submersible, are here simulated, manufactured, and evaluated. Finite element analysis simulations are compared with measurements, and an overall observation is that the agreement between simulations and measurements deviates from the measured values of 1.5 to 2 degrees, for the narrow lobe angle, by less than 10% for most models. An overall finding is that the lobe width along the track direction can be accurately simulated and, hence, the resolution of the sonars can be predicted. This paper presents, to the authors' knowledge, the world's smallest side-scan sonars.

Polishing of quartz by rapid etching in ammonium bifluoride.

The etch rate and surface roughness of polished and lapped AT-cut quartz subjected to hot (90, 110, and 130 degrees C), concentrated (50, 65, 80 wt %) ammonium bi-fluoride have been investigated. Having used principal component analysis to verify experimental solidity and analyze data, we claim with confidence that this parameter space does not, as elsewhere stated, allow for a polishing effect or even a preserving setting. Etch rates were found to correlate well, and possibly logarithmically, with temperature except for the hottest etching applied to lapped material. Roughness as a function of temperature and concentration behaved well for the lapped material, but lacked systematic variation in the case of the polished material. At the lowest temperature, concentration had no effect on etch rate or roughness. Future efforts are targeted at temperatures and concentrations closer to the solubility limit.