NEMS diaphragm sensors integrated with triple-nano-ring resonator

Two types of circular diaphragm, made by Si and Si/SiO₂, integrated with hexagonal photonic crystal (PhC) lattice with triple-nano-ring (TNR) resonator created at the centre are proposed as nano-scale force and pressure sensor. The optimized channel drop effect of the TNR resonator brings a strong forward drop resonant peak in both the cases and with Q-factor of 1602 and 1737, respectively. The resonant wavelength peak experience red shifts upon the applied load on the circular diaphragm along the normal direction, in terms of a 2nd-order polynomial relationship. The devices can detect a wide range of applied load. Si diaphragm based micro force sensor gives minimum detectable force of 0.847 μN in the region of applied force from 10 to 20 μN. Si/SiO₂ diaphragm based pressure sensor gives minimum detectable pressure of 4.17 MPa in the region of applied pressure from 20 to 40 MPa. From the derived wavelength shift versus a given centre displacement of the diaphragm, Si diaphragm based sensor shows higher sensitivity than Si/SiO₂ diaphragm sensor.     

Nanotextured superhydrophobic micromesh

A superhydrophobic micromesh covered with nanoprotrusions has been introduced and its applicability to a waterproof mobile phone speaker has been evaluated. The nanotextured superhydrophobic micromesh showed excellent water repellency, self-cleaning and waterproofing performances. In a waterproof speaker test using the fabricated nanotextured micromesh, the micromesh did not lose its waterproof function at 2 m water depth and did not form a remnant water film after being removed from the water. The packaged speaker showed almost the same sound quality before and after dipping at a 2 m water depth. These results demonstrate that the superhydrophobic nanotextured micromesh could be directly applicable for various products that need to resist water penetration, yet allow the transmission of gases and sound/light waves.     

A resonating rheometer using two polymer membranes for measuring liquid viscosity and mass density

A resonating sensor for mechanical liquid properties facilitating measurements at two different modes of operation is presented. One mode is more sensitive to liquid viscosity the other to mass density. A sample liquid is subjected to time-harmonic shear stress induced by two opposed vibrating polymer membranes. These membranes, placed in an external static magnetic field, carry two conductive paths each. The first path is used to actuate the membranes by means of Lorentz forces while the second acts as a pick-up coil providing an induced voltage representing the movement of the membrane. From the resulting frequency response the liquid's viscosity and mass density can be deduced. This double membrane based setup allows examining the test liquid at adjustable frequencies in the low kilohertz range from 500 Hz to 20 kHz by varying the gap between both membranes. The sensor is suitable, e.g., for low cost handheld devices with inline capabilities and disposable sensor elements for measuring Newtonian liquids such as, e.g., oils and aqueous solutions.     

Study of an innovative one-sided actuating piezoelectric valveless micropump with a secondary chamber

Previous studies have indicated that a one-sided actuating piezoelectric micropump (OAPMP) combined with two valves may enhance the liquid flow rate to 4.1 ml/s and make it possible to reach the maximum pump head of 9807 Pa in a limited space. In this study, an innovative one-sided actuating piezoelectric valveless micropump (OAPMP-valveless) has been developed to actuate fluid at a higher flow rate in one direction by adding a secondary chamber. The secondary chamber plays a key role in the application of the valveless micropump: the flow rate of the pump can reach 0.989 ml/s by adding a secondary chamber. The maximum pump head is 1522.5 Pa when using the 0.3 mm-thick secondary diaphragm and the 0.5 mm-thick primary diaphragm. In addition, if a nozzle/diffuser element is applied to the OAPMP-valveless with a secondary chamber, the flow rate can be further improved to 1.183 ml/s at a frequency of 150 Hz. A three-dimensional numerical model of the valveless micropump has been built to compare the measured results with the simulated results.     

Electro-thermal simulation and characterization of preconcentration membranes

We use electro-thermal simulations to design thermally insulated membranes that support thin film heaters as components of gas preconcentrators. These heaters provide a good thermal homogeneity ensuring a narrow desorption peak and, thus, a good sensor response. Temperature measurements have been carried out using an infrared camera and they are in agreement with the corresponding numerical predictions. Our model has been validated and it can be used in future designs.     

The properties of lattice-shifted microcavity in photonic crystal slab and its applications for electro-optical sensor

In this paper, a micro electro-optic sensor structure and its sensing technique based on lattice-shifted resonant microcavity (H0-nanocavity) in a triangular lattice photonic crystals (PhCs) slab are presented. The H0-nanocavity is formed by only laterally shifting two adjacent holes outwards slightly in the opposite direction, which can realize a nanocavity with high quality factor (Q) value to meet the requirements of practical application. The electro-optic sensor is realized in hole-array based photonic crystal slab with triangular lattice air holes infiltrated with a nonlinear optical (NLO) polymer (n_poly = 1.6) in Silicon-on-Insulator (SOI) operating in the wavelength range from 1400 nm to 1600 nm. The simulation results of PhC electro-sensitive structure show that the optical properties of PhCs can be used to design sensing devices characterized by a high degree of compactness and good resolution. The properties of the sensor are analyzed and calculated using the plane-wave expansion (PWE) method and simulated using the finite-difference time-domain (FDTD) method. The simulation results display that the resonant wavelength of the mode localized in the microcavity shifts its spectral drop position following a linear behavior when a driving voltage ranging between 0.0 V and 3.2 V is applied, and the sensitivity of 31.90 nm/V is observed.     

Study of magnetic ranging technology in horizontal directional drilling

Intersection technology plays a key role in long-distance horizontal directional drilling (HDD). Magnetic ranging technology is an effective way to realize the intersection. A three-dimensional magnetic field model suitable for the cylindrical magnet connected with drilling bit was established. New formulae of magnetic induction intensity were deduced from the fundamental formulae to suit to the new magnetic ranging method. Based on the new formulae, a curve fitting model was established to complete the ranging. The whole process is simple and effective. The result of the experiment proved the feasibility of the new method and the accuracy is high enough for HDD.     

Impact of ZnO gate interfacial layer on piezoelectric response of AlGaN/GaN C-HEMT based ring gate capacitor

We report on a piezoelectric response investigation of AlGaN/GaN circular high electron mobility transistor (C-HEMT) based ring gate capacitor as a new stress sensor device to be potentially applied for dynamic high-pressure sensing. A ring gate capacitor of C-HEMT with an additional ZnO gate interfacial layer was used to measure the changes in the piezoelectric charge induced directly by the variation of piezoelectric polarization of both gate piezoelectric layers (AlGaN, ZnO) for harmonic loading at different excitation frequences. Our experimental results show that about 10 nm thick piezoelectric ZnO layer grown on ring gate/AlGaN interface of C-HEMT can yield almost a 60% increase in the piezoelectric detection sensitivity of the device due to its higher piezoelectric coefficient. A three-dimensional CoventorWare simulation is carried out to confirm the increase in the measured piezoelectric response of ZnO based ring gate capacitor of C-HEMT.     

Control of ignition delay in microfabricated hot-wire igniters: Simulation, fabrication, and experimental results

The presented work studied thermal interactions between laminated, metal-foil, hot-wire igniters and exothermic solid-state, composite chemical systems in order to demonstrate precise timing control of a thermal ignition process. The study includes FEA modeling, device fabrication, and characterization to demonstrate control microthruster ignition delays to within 2 ms. The modeling included studies of total ignition delay as well as the ignition delay variation versus process variations. Microthrusters were then fabricated via printed circuit board lamination, and the ignition performance was characterized. The characterization showed agreement with modeling to within 2-sigma for most cases. And the characterization demonstrated that the ignition delay could be controlled to within 0.36 and 0.84 ms for the best case. Furthermore, this performance was demonstrated with a small battery supply (200-600 mAh) and minimal electronics in the ignition system. This work extends the use of current microthrusters to short-lifetime applications that need high forces delivered in millisecond time intervals.     

Response time of thermal flow sensors with air as fluid

Due to their fast response time miniaturized thermal flow sensors can be applied well for the measurement of instationary gas flow. For some applications, the response time of the sensor must be known with high accuracy. We investigated three methods for response time determination with air: a jump of temperature induced by electric heating, a gas velocity step made by a membrane burst and acoustic phase shifts between sound velocity and sound pressure (standing and traveling waves). The measurements have shown that the response time of thermal flow sensors is a function of flow velocity. For stagnant flow, the thermal response time is about 4.5 ms for our thermal flow sensors. With increasing flow from the heater to the thermopiles, the heat transfer rises. Thus, the response time is faster and decreases to about 1 ms.