A Newly Developed mm-Wave Sensor for Detecting Plaques of Arterial Vessels.

BACKGROUND: Microcalcifications within the fibrous cap of the arteriosclerotic plaques lead to the accrual of plaque-destabilizing mechanical stress. New techniques for plaque screening with small detectors and the ability to differentiate between the smooth and hard elements of plaque formation are necessary. METHOD: Vascular plaque formations are characterized as calcium phosphate containing structures organized as hydroxylapatite resembling the mineral whitlockite. In transmission and reflexion studies with a simple millimeter wave (mm-wave)-demonstrator, we found that there is a narrow window for plaque detection in arterial vessels because of the tissue water content, the differentiation to fatty tissue, and the dielectric property of air or water, respectively. RESULT: The new sensor is based on a sensing oscillator working around 27 GHz. The open-stub capacitance determines the operating frequency of the sensor oscillator. The capacitance depends on the dielectric properties of the surrounding material. The sensor components were completely built up in surface mount technique. CONCLUSION: Completed with a catheter, the sensor based on microwave technology appears as a robust tool ready for further clinical use.

Effect of dexmedetomidine on intracranial pressures during laparoscopic surgery: A randomized, placebo-controlled trial.

BACKGROUND AND AIMS: Laparoscopic surgeries cause an increase in intracranial pressure (ICP) after creation of pneumoperitoneum. Sonographically measured, optic nerve sheath diameter (ONSD) correlates well with changes in ICP. Dexmedetomidine (Dex), an α2 agonist is extensively used in day-care surgeries, although its effect on ICP during laparoscopy in humans has not been reported in the literature. The aim of this study was to note the effect of dexmedetomidine infusion on changes in ICPs during laparoscopic cholecystectomy. MATERIAL AND METHODS: This was a prospective, randomized, placebo-controlled, double-blind study done on 60 patients scheduled for laparoscopic cholecystectomy. The study drug, dexmedetomidine hydrochloride (Dex) or placebo saline infusion, was started 10 min before induction and continued till extubation. Changes in ICP were assessed sonographically at baseline before pneumoperitoneum, 5 min after establishing pneumoperitoneum, 10 min after positioning the patient 20° head up, and 5 min after desufflation. RESULTS: Demographically, both groups were comparable. The ONSD showed a significant increase after pneumoperitoneum in both groups (P = 0.0001 and 0.0011). Dex group could marginally attenuate this increase (P = 0.075). After changing patient's position to reverse Trendelenburg, ONSD increased further in both groups. Dex group could significantly attenuate the increase (P = 0.001). The ONSD did not return to baseline values till after 5 min of release of pneumoperitoneum in both groups. CONCLUSION: Dexmedetomidine is effective in attenuating increase in ICP associated with laparoscopic surgeries. The benefit was marked 10 min after placing patient in the reverse Trendelenburg position during laparoscopic cholecystectomy.

CMOS-compatible optical switching concept based on strain-induced refractive-index tuning.

In this paper we present a planar lightwave switching mechanism based on large refractive index variations induced by electrically-driven strain control in a CMOS-compatible photonic platform. Feasibility of the proposed concept, having general validity, is numerically analyzed in a specific case-study given by a Mach-Zehnder Interferometer with Ge waveguides topped by a piezoelectric stressor. The stressor can be operated in order to dynamically tune the strain into the two interferometric arms. The strain modifies the Ge band structure and can induce refractive index variations up to 0.05. We demonstrate that this approach can enable ultra-compact devices featuring low loss propagation for light wavelengths below the waveguide band gap energy, high extinction ratios (>30 dB) and low intrinsic insertion losses (2 dB). The operation wavelength can be extended in the whole FIR spectrum by using SiGe(Sn) alloy waveguides.

Three-Dimensional Interfacing of Cells with Hierarchical Silicon Nano/Microstructures for Midinfrared Interrogation of In Situ Captured Proteins.

Label-free optical detection of biomolecules is currently limited by a lack of specificity rather than sensitivity. To exploit the much more characteristic refractive index dispersion in the mid-infrared (IR) regime, we have engineered three-dimensional IR-resonant silicon micropillar arrays (Si-MPAs) for protein sensing. By exploiting the unique hierarchical nano- and microstructured design of these Si-MPAs attained by CMOS-compatible silicon-based microfabrication processes, we achieved an optimized interrogation of surface protein binding. Based on spatially resolved surface functionalization, we demonstrate controlled three-dimensional interfacing of mammalian cells with Si-MPAs. Spatially controlled surface functionalization for site-specific protein immobilization enabled efficient targeting of soluble and membrane proteins into sensing hotspots directly from cells cultured on Si-MPAs. Protein binding to Si-MPA hotspots at submonolayer level was unambiguously detected by conventional Fourier transform IR spectroscopy. The compatibility with cost-effective CMOS-based microfabrication techniques readily allows integration of this novel IR transducer into fully fledged bioanalytical microdevices for selective and sensitive protein sensing.

Towards CMOS Integrated Microfluidics Using Dielectrophoretic Immobilization.

Dielectrophoresis (DEP) is a nondestructive and noninvasive method which is favorable for point-of-care medical diagnostic tests. This technique exhibits prominent relevance in a wide range of medical applications wherein the miniaturized platform for manipulation (immobilization, separation or rotation), and detection of biological particles (cells or molecules) can be conducted. DEP can be performed using advanced planar technologies, such as complementary metal-oxide-semiconductor (CMOS) through interdigitated capacitive biosensors. The dielectrophoretically immobilization of micron and submicron size particles using interdigitated electrode (IDE) arrays is studied by finite element simulations. The CMOS compatible IDEs have been placed into the silicon microfluidic channel. A rigorous study of the DEP force actuation, the IDE's geometrical structure, and the fluid dynamics are crucial for enabling the complete platform for CMOS integrated microfluidics and detection of micron and submicron-sized particle ranges. The design of the IDEs is performed by robust finite element analyses to avoid time-consuming and costly fabrication processes. To analyze the preliminary microfluidic test vehicle, simulations were first performed with non-biological particles. To produce DEP force, an AC field in the range of 1 to 5 V (peak-to-peak) is applied to the IDE. The impact of the effective external and internal properties, such as actuating DEP frequency and voltage, fluid flow velocity, and IDE's geometrical parameters are investigated. The IDE based system will be used to immobilize and sense particles simultaneously while flowing through the microfluidic channel. The sensed particles will be detected using the capacitive sensing feature of the biosensor. The sensing and detecting of the particles are not in the scope of this paper and will be described in details elsewhere. However, to provide a complete overview of this system, the working principles of the sensor, the readout detection circuit, and the integration process of the silicon microfluidic channel are briefly discussed.

Design and Fabrication of a BiCMOS Dielectric Sensor for Viscosity Measurements: A Possible Solution for Early Detection of COPD.

The viscosity variation of sputum is a common symptom of the progression of Chronic Obstructive Pulmonary Disease (COPD). Since the hydration of the sputum defines its viscosity level, dielectric sensors could be used for the characterization of sputum samples collected from patients for early diagnosis of COPD. In this work, a CMOS-based dielectric sensor for the real-time monitoring of sputum viscosity was designed and fabricated. A proper packaging for the ESD-protection and short-circuit prevention of the sensor was developed. The performance evaluation results show that the radio frequency sensor is capable of measuring dielectric constant of biofluids with an accuracy of 4.17%. Integration of this sensor into a portable system will result in a hand-held device capable of measuring viscosity of sputum samples of COPD-patients for diagnostic purposes.

A Review on Passive and Integrated Near-Field Microwave Biosensors.

In this paper we review the advancement of passive and integrated microwave biosensors. The interaction of microwave with biological material is discussed in this paper. Passive microwave biosensors are microwave structures, which are fabricated on a substrate and are used for sensing biological materials. On the other hand, integrated biosensors are microwave structures fabricated in standard semiconductor technology platform (CMOS or BiCMOS). The CMOS or BiCMOS sensor technology offers a more compact sensing approach which has the potential in the future for point of care testing systems. Various applications of the passive and the integrated sensors have been discussed in this review paper.

Geometric conductive filament confinement by nanotips for resistive switching of HfO2-RRAM devices with high performance.

Filament-type HfO2-based RRAM has been considered as one of the most promising candidates for future non-volatile memories. Further improvement of the stability, particularly at the "OFF" state, of such devices is mainly hindered by resistance variation induced by the uncontrolled oxygen vacancies distribution and filament growth in HfO2 films. We report highly stable endurance of TiN/Ti/HfO2/Si-tip RRAM devices using a CMOS compatible nanotip method. Simulations indicate that the nanotip bottom electrode provides a local confinement for the electrical field and ionic current density; thus a nano-confinement for the oxygen vacancy distribution and nano-filament location is created by this approach. Conductive atomic force microscopy measurements confirm that the filaments form only on the nanotip region. Resistance switching by using pulses shows highly stable endurance for both ON and OFF modes, thanks to the geometric confinement of the conductive path and filament only above the nanotip. This nano-engineering approach opens a new pathway to realize forming-free RRAM devices with improved stability and reliability.