The Accurate Measurement of a Micromechanical Force Using Force-Sensitive Capacitances

A sensor for the precise and accurate measurement of micromechanical forces is presented. The sensor is based on the capacitive detection of force-induced deflection of a microstructure and integrated charge readout. The mechanical performance of the sensor is evaluated and verified with experiments. The structure has been designed to enable the separation of the force-to-deflection and deflection measurements in order to result in a sensor structure in which the response is linear with force and little affected by fringe fields. The sensor is 0.25 mm2 in size and has a force range of 0.2 mN, a zero-force capacitance of 0.5 pF, a sensitivity of 1-5 fF/uN, and a resolution that corresponds to a capacitance variation of 2 f

Diagnosis of Gestational Diabetes Mellitus

Gestational diabetes mellitus (GDM) is associated with a high risk of obstetric and neonatal complications. Adequate diagnosis and appropriate treatment are key to prevention of these complications. Most international guidelines have adopted the IADPSG 2010/WHO 2013 diagnostic criteria, for the diagnosis of GDM by recommending the following glycemic thresholds for a 75 g OGTT: fasting plasma glucose value =5.1 mmol/l (92 mg/dl); 1-h value =10.0 mmol/l (180 mg/dl); and 2-h value =8.5 mmol/l (153 mg/dl). These specific cut-off values were chosen because they predict a 75% higher chance of adverse pregnancy outcomes compared to normal glucose values. Some countries have adopted either higher levels for fasting glucose (5.6 or 7.0 mmol/l) or lower levels for 2-h post-OGTT glucose (7.8 mmol/l). There still is some debate whether it is desirable to lower the diagnostic 2-h glucose thresholds to =7.5 mmol/l for Caucasian women and =7.2 mmol/l for women from South Asian background. Several studies have shown that about 20-30% (depending on the applied diagnostic criteria) of the women screened for GDM had/have abnormal OGTT results, necessitating referral, active counseling, and treatment. By adopting the new IADPSG/WHO diagnostic criteria, the prevalence of GDM has increased, which has a major impact on the costs and the capacity of healthcare systems. Screening for GDM may follow either a one-step or a two-step approach. In the one-step approach, GDM is diagnosed based on the results of a single 75 g OGTT. The two-step screening strategy makes use of a non-fasting 50 g glucose challenge test (GCT), whereby an abnormal test result (i.e., a 1-h plasma glucose value =7.8 mmol/l) is followed by a 100 g OGTT. There also is no international consensus on whether universal or risk factor-based screening is preferred. Universal screening implies that all pregnant women will undergo screening between 24 and 28 weeks of pregnancy, while in selective screening, only women who have specific risk factors for developing GDM or who exhibit a possible consequence of hyperglycemia, i.e., macrosomia or polyhydramnios, will undergo an OGTT. Most studies comparing these strategies have mainly reported data on GDM classification, not on GDM treatment or, even better, pregnancy outcomes. Some countries, therefore, follow a hybrid approach of partly risk factor-based and partly universal screening. Recently published systematic economic evaluations support universal screening and the one-step approach as a more likely cost-effective strategy.</p

Lab-on-a-chip for biological fluids analysis by spetrophotometry

The healthcare sector is nowadays one of the most dynamic and where the novelty is a strategic and operational imperative. The possibility of increase the quantity and quality of clinical analysis, performed with instantaneous results and outside the clinical laboratories, contributes to a better quality in the health care services and also a better efficiency in the clinical and administrative processes [1]. This possibility can be achieved with the presented lab-on-a-chip for spectrophotometric analysis of biological fluids. It allows the selective measurement of the concentration of several biomolecules in biological fluids, with instantaneous results, at any location, with small quantities of reagents and samples and with low-cost. That measurement is based on colorimetric detection by the optical absorption in a part of the visible spectrum defined by the reaction of the specific biomolecule with a specific reagent. The device comprises a highly efficient and selective optical filtering and colorimetric detection system. This system allows the measurement with a regular white light illumination, thus avoiding the use of complex and expensive analysis systems like the ones that comprise spectrophotometers, for example. This feature highly facilitates portability and ensures analysis within consultation time, at a patient house (allowing a first trial) and in clinical laboratories or hospitals.Fundação para a Ciência e a Tecnologia (FCT) SFRH/BD/1281/2000 Escola de Engenharia da Universidade do Minho - Projecto IN2TEC. Centro Algoritmi da Universidade do Minh

High-selectivity single-chip spectrometer for operation at visible wavelengths

A micro-spectrometer has been realized based on an array of Fabry-Perot thin-film optical resonators. The 16 channel micro-spectrometer is IC fabrication compatible and operates in the visible spectral range with an inter-channel shift of 6 nm. Each of the channels is sensitive in a single peak with FWHM of 16 nm. A FWHM < 2 nm and finesse of 40 for narrowband operation is demonstrated.STW - Project DEL 55.3733. TUDelft. Fundação para a Ciência e Tecnologia - Praxis XXI-BD/5181/95

Micromachined fabry-perot optical filters

The design, fabrication and measured characteristics of micromachined Fabry- Perot (F-P) optical filters for the visible spectral range are presented. Silver films of 40-50 nm thickness, evaporated on a 300 nm thick low-stress silicon nitride membrane, are used as high-quality mirrors. Two parallel mirrors, with a square aperture of up to 2x2 mm2 and initial cavity gap of 1.2 µm, form a tunable Fabry- Perot optical filter. One of the mirrors is fixed the other is under tension on a movable Si frame, which is electrostatically deflected to control the mirror spacing and parallelism. Results are compared with non-tunable F-P filters that are composed of an Ag/SiN/Ag or Ag/SiO2/Al layer stack. The FWHM of 40 nm (tunable filter) and 16 nm (non-tunable filter) have been achieved.STW - Project DEL 55.3733. Junta Nacional de Investigação Científica e Tecnológica - PRAXIS XXI-BD/5181/95

High-selectivity single-chip spectrometer in silicon for operation at visible part of the spectrum

A microspectrometer has been realized based on an array of Fabry–Perot optical thin-film filters. The 16-channel microspectrometer is compatible with IC fabrication methods and operates in the visible spectral range with an interchannel shift of 6 nm. Each of the channels is sensitive in a single peak with full-width-half-maximum (FWHM) of 16 nm. Also aFWHMbelow 2 nm and finesse of 40 for narrow band operation is demonstrated. The device can easily be tuned during fabrication to cover a different spectral band only by adjusting the etching times without affecting the device layout. Such a device is extremely suitable for applications in microsystems because of its small size, high spectral selectivity, and low cost. Microspectrometers for the UV and IR regions are also feasible using this technique.Fundação para a Ciência e a Tecnologia (FCT

Silver-based reflective coatings for micromachined optical filters

Silver films of 40 nm thickness, evaporated on a 300 nm thick low-stress silicon nitride layer, are used as high-quality mirrors operating in the visible and near IR spectral range. Application of a silicon nitride membrane under tension, placed within a square Si frame after bulk micromachining, improves the initial mirror flatness. Two parallel mirrors, each with square aperture of up to 2x2 mm2 and an electrostatically controlled spacing, form a tunable Fabry–P´erot optical filter. Investigation of the silver-based reflective coatings, and mirror characterization, including influence of bulk micromachining, are presentedFundação para a Ciência e a Tecnologia FC