Binghe Ma

Flexible thermal sensor array on PI film substrate for underwater applications

Fully flexible thermal sensor array was developed for underwater applications. To minimize conductive heat loss to substrate and shorten response time nickel thin film resistors are fabricated on polyimide film substrate. This flexible sensing belt can be applied onto highly curved non-planar surfaces to measure flow with minimal invasion. Polymer compatible micromachining technology with consideration of waterproof coating was developed. Through calibration performed under constant-current excitation, high temperature coefficient of resistance (TCR) and low time constant of sensor were obtained. Hydrodynamic experiments in water channels were carried out, and it indicates dynamic wave flow can be sensed promptly with this sensing belt.

System-level modeling of segmented deformable micromirror using multi-port-element network method

This paper presents the development of system-level modeling and simulation of segmented deformable micromirror. We represent a system-level modeling methodology called Multi-Port-Element Network (MuPEN) method for micromirror design which is different from conventional finite-element analysis(FEA) and boundary-element analysis(BEA) method in the paper. Based on this method, the segmented deformable micromirror is decomposed into functional components such as rigid plate-mass, spring beam and electrostatic gap. MuPEN models of functional components have been generated and are coded in MAST language. Then a system-level model of segmented deformable micromirror is established using MuPEN models and both static and dynamic simulation is implemented in SABER. The resonance frequency, the pull-in voltage and the response time of the micromirror are ascertained through different simulations and the simulation results show that the micromirror we designed can satisfy the adaptive optical system requirements. Besides, the frequency analysis results are verified by comparison with ANSYS simulations, and the results prove that MuPEN method has near FEM accuracy. In addition, transient analysis results indicate that the computation cost is low enough and the simulation of complicated electro-mechanical coupled system which is hardly completed by FEM software can be accomplished quickly in this way.

Design and fabrication of a Piezoelectric Micro Synthetic Jet Actuator

Synthetic Jet Actuator (SJA) is a new type actuator for active flow control applications. A Piezoelectric Micro SJA based on MEMS technology was present in this work. The simulation of device performance was carried out through a multi-domain coupled analysis model, and the relative error of jet velocity between simulation results and experiment data is less than 8%. A batch fabrication process was proposed to integrated fabrication of piezoelectric film and silicon structure. And using this process, prototype of micro SJA was gained. Preliminary tests of SJAs performance show that the max synthetic jet velocity (8.2m/s) is obtained as driving voltage is 25V and driving frequency close to the first-order natural frequency (10500Hz).

Angularly parameterized macromodel extraction for unconstrained microstructures

In this paper, we present an angularly parameterized model order reduction (APMOR) technique for macromodel extraction of unconstrained microstructures by combining a new, iterated IRS (improved reduced system) method with coordinate transformation theory. The extracted macromodels are encapsulated in the MAST hardware description language and can be exported automatically as components which can be inserted directly into an analog circuit simulator for dynamics simulation. An in-plane micro accelerometer including four variable cross-section folded beams is used to demonstrate the proposed macromodeling method. The folded beams are treated as unconstrained microstructures, and numerical simulation results in a SABER simulator show that the macromodels can dramatically reduce the computation cost while capturing the device behavior faithfully. Compared with FEM results, the relative error is less than 1.4%, while the computational efficiency improves about 22 times. Once the macromodel of one of the folded beams is obtained, the macromodels of all other folded beams can be obtained easily by setting the corresponding angle parameters. With the help of an APMOR technique and the existing model library which is developed in our previous work, the hybrid system-level model of the in-plane micro accelerometer can be constructed rapidly, and the scale factor of the accelerometer is simulated. Compared with experimental results, the relative error is about 8.16%.

ITO thin film thermocouple for transient high temperature measurement in scramjet combustor

Thin film thermocouples have high respond speed and measuring accuracy of the dynamic surface temperature for their negligible thermal mass. In this paper, ITO thin film thermocouples were used to capture the transient wall temperature in supersonic combustor. A protective bilayer was used to improve the sensors thermal stability and durability. Calibration results show that the sensor exhibit high thermal stability over 1600K for 300 minutes. And a relationship was established to describe the thermoelectricity of ITO thin film thermocouples. The dynamic temperature of scramjets inner wall was successfully captured and the combustion procedure was characterized clearly.

High temperature thin film thermocouples on different ceramic substrates

This paper was directed at the effect of ceramic substrate on NiCr/NiSi film thermocouples fabricated on two ceramics substrate. One was on smooth Al2O3 substrate. The other was on silicon carbide ceramic reinforced by carbon fiber (CFCC-SiC). Since the CFCC-SiC has rough surface, the stress between the layer was greater and the thin film was easier to crack. With experiments the measure temperature of the thin film thermocouples on both of them could reach 700°C. Calibrate test data showed that the high-temperature stability of the thin film thermocouple on smooth Al2O3 substrate was much better than the other.

Fully flexible hot film sensor array for underwater applications

Flexible hot film sensor array was developed for underwater applications. To minimize conductive heat loss to substrate, heighten sensitivity and shorten response time nickel thin film resistors are fabricated on polyimide substrate. Fully flexible structure and very low thickness of the sensing belt enable it possible to be taped on highly curved surfaces to measure fluid parameters with minimal invasion. Polymer compatible micromachining technologies with further consideration of waterproof coating were developed. High temperature coefficient of resistance (TCR) and low time constant of sensor were obtained. A hydrodynamic experimental setup was established, and a demonstration indicated flow velocity can be measured with the sensor.

Accurate Measurements of Wall Shear Stress on a Plate with Elliptic Leading Edge

A micro-floating element wall shear stress sensor with backside connections has been developed for accurate measurements of wall shear stress under the turbulent boundary layer. The micro-sensor was designed and fabricated on a 10.16 cm SOI (Silicon on Insulator) wafer by MEMS (Micro-Electro-Mechanical System) processing technology. Then, it was calibrated by a wind tunnel setup over a range of 0 Pa to 65 Pa. The measurements of wall shear stress on a smooth plate were carried out in a 0.6 m × 0.6 m transonic wind tunnel. Flow speed ranges from 0.4 Ma to 0.8 Ma, with a corresponding Reynold number of 1.05 × 106~1.55 × 106 at the micro-sensor location. Wall shear stress measured by the micro-sensor has a range of about 34 Pa to 93 Pa, which is consistent with theoretical values. For comparisons, a Preston tube was also used to measure wall shear stress at the same time. The results show that wall shear stress obtained by three methods (the micro-sensor, a Preston tube, and theoretical results) are well agreed with each other.

A Flexible Hot-Film Sensor Array for Underwater Shear Stress and Transition Measurement

A flexible hot-film sensor array for wall shear stress, flow separation, and transition measurement has been fabricated and implemented in experiments. Parylene C waterproof layer is vapor phase deposited to encapsulate the sensor. Experimental studies of shear stress and flow transition on a flat plate have been undertaken in a water tunnel with the sensor array. Compared with the shear stress derived from velocity profile and empirical formulas, the measuring errors of the hot-film sensors are less than 5%. In addition, boundary layer transition of the flat plate has also been detected successfully. Ensemble-averaged mean, normalized root mean square, and power spectra of the sensor output voltage indicate that the Reynolds number when transition begins at where the sensor array located is 1.82 × 105, 50% intermittency transition is 2.52 × 105, and transition finishes is 3.96 × 105. These results have a good agreement with the transition Reynolds numbers, as measured by the Laser Doppler Velocimetry (LDV) system.

A High-Temperature MEMS Surface Fence for Wall-Shear-Stress Measurement in Scramjet Flow

A new variant of MEMS surface fence is proposed for shear-stress estimation under high-speed, high-temperature flow conditions. Investigation of high-temperature resistance including heat-resistant mechanism and process, in conjunction with high-temperature packaging design, enable the sensor to be used in environment up to 400 °C. The packaged sensor is calibrated over a range of ~65 Pa and then used to examine the development of the transient flow of the scramjet ignition process (Mach 2 airflow, stagnation pressure, and a temperature of 0.8 MPa and 950 K, respectively). The results show that the sensor is able to detect the transient flow conditions of the scramjet ignition process including shock impact, flow correction, steady state, and hydrogen off.