We report the fabrication and evaluation of a PMMA electrostatic comb-drive microactuator using hot embossing and ultra-precision cutting technology. First, a two-step silicon mold is fabricated by bulk micromachining technology. Next, comb-drive microactuator structures are formed on a PMMA plate by hot embossing. Both finger width and gap between fingers are 5 µm, and finger thickness is larger than 70 µm. Then, the PMMA layer that remained after hot embossing is removed by ultra-precision cutting to release the movable parts. Last, the device is coated with a gold layer for the electrode. The PMMA comb-drive microactuator has been tested successfully.
This paper reports on the design and simulation of a new valve-less pump for use in microfluidic applications. The
simple-structure micropump comprises a piezoelectric Pb(Zr,Ti)O3 (PZT) - Si diaphragm and flow channels which are
fabricated using silicon micromachining techniques. The silicon diaphragm (5×5×0.05mm3) is driven by the PZT (45-μm
thick) actuator that has quick response time and large driving force with low power consumption. A key technology to
realize the pump diaphragm is the PZT-Si bonding process using a thin gold film as an intermediate layer. Under
fabrication conditions of 550°C and 0.8 MPa, the strength of the bonding was experimentally validated to be 13 MPa.
The maximum displacement of the diaphragm was measured to be 3 μm0-P with driving voltage of 30 Vp-p at resonance
frequency of 10 kHz. Structural analysis of the diaphragm was done in terms of three-dimensional model using
commercial software ANSYS. The flow channels are easily fabricated by silicon etching process. Design of flow
channels focused on a cross junction formed by neck of the pump chamber, one outlet and two opposite inlet channels.
This structure allows a difference in fluidic resistance and fluidic momentum to be created inside the channels during
each pump vibration cycle. Two designs of the devices which have different channel depths, namely type A and type B,
was investigated. Flow simulation was done by numerical transient model (using ANSYS-Fluent), in which only the
measured deformation of the PZT diagram is applied and therefore no other assumptions are required. The results
showed that the mass flow rate of the type A is 0.129×10-6 kg/s (mean flow rate of 6.3 ml/min) and that of type B is
1.65×10-6 kg/s (mean flow rate of 80.8 ml/min).
This paper presents our latest results on the designs, fabrication and calibration of two micro accelerometers and a convective based gyroscope, as well as their combination to create a motion sensor for inertial navigation applications. Among the two accelerometers, the first one is a 3-DOF micro accelerometer utilizing piezoresistive effect in single crystal silicon. The sensing structure consists of four sensing-beams surrounding a seismic-mass. Therefore, the sensor is smaller than the cross-beam type accelerometer. The second accelerometer is a dual axis thermal accelerometer, working based on the thermo-resistive effect of silicon thermistors in free convective regime. Since no seismic mass is used, the shock-resistance becomes very high (up to 9.0×106g). The novel structure of the thermistors eliminated up to 93% of stress induced by temperature. The dual-axis gas gyroscope proposed here is working based on the thermo-resistive effect of light-doped silicon thermistor and the force convective heat transfer. The sensor configuration consists of a gas pump and a micro thermistor sensing element, packaged in an aluminum case with overall diameter and length of 14mm and 25mm, respectively. Unlike vibrating gyroscopes reported recently in MEMS-field, our gyroscope has "no" seismic mass; therefore it can eliminate the inherent problems such as fragility, low shock-resistance, squeezed-film air-damping, etc. Moreover, since the driving power for the moving mass is not necessary, the power consumption is also reduced. Finally, an algorithm to process the signal from a system consists of a 3-DOF accelerometer and 3-DOF gyroscope is presented. In this algorithm, quaternion based calculation was applied instead of Euler angles, therefore the problems of singularity or complicated trigonometric calculations can be avoided. The algorithm can be applied for inertial navigation systems (INS).