Microcantilever based LoC system for coagulation measurements

In this paper, a microcantilever-based system enabling multiple coagulation tests on the same disposable cartridge is demonstrated. The system consists of independent cartridge and reader unit. The actuation of the nickel cantilevers is conducted remotely with an external electro-coil and remote optical read-out is utilized for sensing. Both Prothrombin Time (PT) and activated Partial Thromboplastin Time (aPTT) tests can be conducted on the same cartridge. The system’s repeatability and accuracy is investigated with standard control plasma samples. The results are concordant with the manufacturer’s datasheet. The architecture of the system and the repeatable results makes the system suitable for Point-of-Care applications.TÜBİTA

Microcantilever based LoC system for coagulation measurements

In this paper, a microcantilever-based system enabling multiple coagulation tests on the same disposable cartridge is demonstrated. The system consists of independent cartridge and reader unit. The actuation of the nickel cantilevers is conducted remotely with an external electro-coil and remote optical read-out is utilized for sensing. Both Prothrombin Time (PT) and activated Partial Thromboplastin Time (aPTT) tests can be conducted on the same cartridge. The system’s repeatability and accuracy is investigated with standard control plasma samples. The results are concordant with the manufacturer’s datasheet. The architecture of the system and the repeatable results makes the system suitable for Point-of-Care applications.TÜBİTA

Microcantilever based disposable viscosity sensor for serum and blood plasma measurements

This paper proposes a novel method for measuring blood plasma and serum viscosity with a microcantilever-based MEMS sensor. MEMS cantilevers are made of electroplated nickel and actuated remotely with magnetic field using an electro-coil. Real-time monitoring of cantilever resonant frequency is performed remotely using diffraction gratings fabricated at the tip of the dynamic cantilevers. Only few nanometer cantilever deflection is sufficient due to interferometric sensitivity of the readout. The resonant frequency of the cantilever is tracked with a phase lock loop (PLL) control circuit. The viscosities of liquid samples are obtained through the measurement of the cantilever's frequency change with respect to a reference measurement taken within a liquid of known viscosity. We performed measurements with glycerol solutions at different temperatures and validated the repeatability of the system by comparing with a reference commercial viscometer. Experimental results are compared with the theoretical predictions based on Sader's theory and agreed reasonably well. Afterwards viscosities of different Fetal Bovine Serum and Bovine Serum Albumin mixtures are measured both at 23. °C and 37. °C, body temperature. Finally the viscosities of human blood plasma samples taken from healthy donors are measured. The proposed method is capable of measuring viscosities from 0.86. cP to 3.02. cP, which covers human blood plasma viscosity range, with a resolution better than 0.04. cP. The sample volume requirement is less than 150. μl and can be reduced significantly with optimized cartridge design. Both the actuation and sensing are carried out remotely, which allows for disposable sensor cartridges. © 2013

舞踏病ト妊娠トノ関係ニ就テ

<div><p>The role of hemodynamic forces within the embryo as biomechanical regulators for cardiovascular morphogenesis, growth, and remodeling is well supported through the experimental studies. Furthermore, clinical experience suggests that perturbed flow disrupts the normal vascular growth process as one etiology for congenital heart diseases (CHD) and for fetal adaptation to CHD. However, the relationships between hemodynamics, gene expression and embryonic vascular growth are poorly defined due to the lack of concurrent, sequential <i>in vivo</i> data. In this study, a long-term, time-lapse optical coherence tomography (OCT) imaging campaign was conducted to acquire simultaneous blood velocity, pulsatile micro-pressure and morphometric data for 3 consecutive early embryonic stages in the chick embryo. In conjunction with the <i>in vivo</i> growth and hemodynamics data, <i>in vitro</i> reverse transcription polymerase chain reaction (RT-PCR) analysis was performed to track changes in transcript expression relevant to histogenesis and remodeling of the embryonic arterial wall. Our non-invasive extended OCT imaging technique for the microstructural data showed continuous vessel growth. OCT data coupled with the PIV technique revealed significant but intermitted increases in wall shear stress (WSS) between first and second assigned stages and a noticeable decrease afterwards. Growth rate, however, did not vary significantly throughout the embryonic period. Among all the genes studied, only the MMP-2 and CASP-3 expression levels remained unchanged during the time course. Concurrent relationships were obtained among the transcriptional modulation of the genes, vascular growth and hemodynamics-related changes. Further studies are indicated to determine cause and effect relationships and reversibility between mechanical and molecular regulation of vasculogenesis.</p></div

Precision density and viscosity measurement using two cantilevers with different widths

Due to copyright restrictions, the access to the full text of this article is only available via subscription.We introduce a novel method for fast measurement of liquid viscosity and density using two cantilevers with different geometries. Our method can be used for real-time monitoring in lab on chip systems and offer high accuracy for a large range of densities and viscosities. The measurement principle is based on tracking the oscillation frequencies of two cantilevers with a phase-locked loop (PLL) and comparing with reference measurements with a known fluid. A set of equations and a simple algorithm is developed to relate the density and the viscosity to the frequency shifts of the cantilevers. We found that the effect of the density and the viscosity can be well separated if cantilevers have different widths. In the experiments, two Nickel microcantilevers (widths 25 μm and 100 μm, length: 200 μm, thickness: 1.75 μm) were fully immersed in the liquid and the temperature was controlled. The actuation was using an external electro-coil and the oscillations were monitored using laser Doppler vibrometer. Thus, electrical connections to the cantilevers are not required, enabling measurements also in conductive liquids. The PLL is used to set the phase difference to 90° between the actuator and the sensor. Calibration measurements were performed using glycerol and ethylene glycol solutions with known densities and viscosities. The measurement error with the new method was lower than 3% in density in the range 995–1150 kg/m3 and 4.6% in viscosity in the range 0.935–4 mPa.s. Based on the signal-to-noise ratio, the minimum detectable difference in the viscosity is 1 μPa.s and the density is 0.18 kg/m3. Further improvements in the range and the accuracy are possible using 3 or more cantilevers with different geometries.TÜBİTA

Two cantilever based sytem for viscosity and density monitoring

Due to copyright restrictions, the access to the full text of this article is only available via subscription.Viscosity and density measurements in liquids in real-time is challenging. Previous MEMS based approaches use frequency sweeps for the purpose and those methods are slow and not real-time. We show that high precision viscosity and density measurements are possible using two cantilevers with different widths and by tracking their frequencies with a Phase-Locked-Loop in real-time.TÜBİTA

Precision density and viscosity measurement using two cantilevers with different widths

Due to copyright restrictions, the access to the full text of this article is only available via subscription.We introduce a novel method for fast measurement of liquid viscosity and density using two cantilevers with different geometries. Our method can be used for real-time monitoring in lab on chip systems and offer high accuracy for a large range of densities and viscosities. The measurement principle is based on tracking the oscillation frequencies of two cantilevers with a phase-locked loop (PLL) and comparing with reference measurements with a known fluid. A set of equations and a simple algorithm is developed to relate the density and the viscosity to the frequency shifts of the cantilevers. We found that the effect of the density and the viscosity can be well separated if cantilevers have different widths. In the experiments, two Nickel microcantilevers (widths 25 μm and 100 μm, length: 200 μm, thickness: 1.75 μm) were fully immersed in the liquid and the temperature was controlled. The actuation was using an external electro-coil and the oscillations were monitored using laser Doppler vibrometer. Thus, electrical connections to the cantilevers are not required, enabling measurements also in conductive liquids. The PLL is used to set the phase difference to 90° between the actuator and the sensor. Calibration measurements were performed using glycerol and ethylene glycol solutions with known densities and viscosities. The measurement error with the new method was lower than 3% in density in the range 995–1150 kg/m3 and 4.6% in viscosity in the range 0.935–4 mPa.s. Based on the signal-to-noise ratio, the minimum detectable difference in the viscosity is 1 μPa.s and the density is 0.18 kg/m3. Further improvements in the range and the accuracy are possible using 3 or more cantilevers with different geometries.TÜBİTA

MEMS based blood plasma viscosity sensor without electrical connections

Due to copyright restrictions, the access to the full text of this article is only available via subscription.A MEMS based viscometer is reported. The device has a disposable cartridge and a reader. The cartridge contains microfluidic channels and a MEMS cantilever sensor. The reader contains the actuator and the readout optics and electronics. A unique feature of the system is that both the actuation and the sensing are remote; therefore, no electrical connections are required between the reader and the cartridge. The reported sensor is capable of measuring viscosity with better than 0.01 cP resolution in a range of 0.8-14.1 cP, with less than 50 μl sample requirement. This range and sensitivity are sufficient for blood plasma viscosity measurements, which are in between 1.1-1.3 cP for healthy individuals and can be elevated to 3cP in certain diseases[1].TÜBİTA

SIMULTANEOUS SELF-SUSTAINED ACTUATION AND PARALLEL READOUT WITH MEMS CANTILEVER SENSOR ARRAY

Parallel readout of a microcantilever array using single magnetic actuator and a single photo detector for concurrent detection is reported. The system includes MEMS cantilever array designed for different resonance frequencies, optical elements for laser beam shaping and focusing, one detector and feedback electronics, and single broadband actuator for parallel excitation. The cantilevers are made using a simple one-mask fabrication process with embedded amplitude gratings at the tips. A line shaped laser beam is used to illuminate the cantilevers. A single readout photodiode is placed at the first order diffraction beam location on the Fourier plane. The amplified photodiode signal is fed back into the magnetic actuation using a preamplifier and a broadband current amplifier. In this paper, we report for the first time parallel monitoring of the thermal resonance peaks of inherently frequency-multiplexed MEMS cantilevers. We demonstrated simultaneous self-sustained oscillations of seven cantilevers by using a single actuator and detector in air environment. The method is suitable for low-cost multiplexed portable biosensors