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MEMS based blood plasma viscosity sensor without electrical connections

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].

LoC sensor array platform for real-time coagulation measurements

This paper reports a MEMS-based sensor array enabling multiple clot-time tests in one disposable microfluidic cartridge using plasma. The versatile LoC (Lab-on-Chip) platform technology is demonstrated here for real-time coagulation tests (activated Partial Thrompoblastin Time (aPTT) and Prothrombin Time (PT)). The system has a reader unit and a disposable cartridge. The reader has no electrical connections to the cartridge, which consists of multiple microfluidic channels and MEMS microcantilevers placed in each channel. Microcantilevers are made of electro-plated nickel and actuated remotely using an external electro-coil. The read-out is also conducted remotely by a laser and the phase of the MEMS oscillator is monitored real-time. The system is capable of monitoring coagulation time with a precision estimated at 0.1sec.

Optical sensor for humidity and hydrogen gas based on polymer microresonators

Summary form only given. We report humidity and hydrogen sensors employing elastic polymer (SU-8) optical microresonators fabricated with photolithography. The sensing mechanism relies on monitoring the spectral shifts of the optical whispering gallery modes (WGMs) in the transmission spectra recorded from the microresonators. WGMs are excited through SU-8 waveguides in which a tunable laser light is coupled from an optical fiber.

Two cantilever based sytem for viscosity and density monitoring

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.

Hydrogen gas sensing using palladium-coated microdisk microresonators

An SU-8 polymer microdisk resonator coated with a palladium (Pd) layer and coupled to a single-mode optical waveguide is used to as a hydrogen (H2) gas sensor. In the presence of H2, a red shift is observed in the spectral positions of the microdisk whispering gallery modes (WGMs) due to the expansion in the Pd lattice. H2 concentrations below the flammable limit (4%) down to 0.3% could be detected in nitrogen atmosphere at room temperature. For H2 concentrations between 0.3 − 1%, WGM spectral positions shifted linearly with H2 concentration at a rate of 32 pm/%H2. Average response time of the devices was measured to be 50 s for 1% H2. The proposed device concept can also be used to detect different chemical gases by using appropriate sensing layers.