The purpose of this study is to systematically evaluate the performance of a portable chemical fume
extractor used for cleaning chemical fume in small work places. Four chemical liquids, a closed chamber,
and a metal-oxide sensor were used to evaluate its performance. The experimental results show that the
unit under test is able to extract high concentrations of the tested chemical vapors and the cleaning
processes take 5 minutes in average to clean out a strong-smelling fume concentration of 29 ppm. The
performance is evaluated in terms of the cleaning efficiency (η) and clean air delivery rate (CADR).
A wireless batteryless piezoresistive pressure sensing system was presented. The sensing system adapts
RFID operation principles including a transponder and a reader. The transponder device includes an
energy harvesting circuit, force sensing resistors, a resistance-to-frequency converter, and an antenna. The
reader provides radio frequency power to the device remotely and measures the sensor values in terms of
frequency shift simultaneously. The performance of the system was characterized form 0 to 10 psi while
the corresponding modulated frequency shift by the reader was between 7.35 kHz and 8.55 kHz. A
pressure sensor array was arranged to identify high pressure points dynamically for long-term usage.
In this paper, we presented the fabrication process of miniature pH sensor arrays on flexible polymer
substrates. The repeatability of the sensors based on sol-gel fabrication processes was investigated. The
sensor repeatability was characterized with linearity, decay time, environmental parameter control and
potential stability. Similar linear responses were found in different batches of sensor arrays. Near super-
Nernstian responses were measured on each sensor with slope ranges from
-71.6 to -110 mV/pH within a
pH range between 2 and 12. The response times were compared in different batches. Six to twenty five
seconds of average decay time were shown in each sample repeatedly. Three sensors showed the close
potential response in different volumes of pH buffer solution. The sensor showed good stability in each
step of the titration process between pH values of 1.8 and 11.9. The peak and saturated potential values
presented high correlation with pH values with minor noises. The results showed good sensitivity,
stability and repeatability using the sol-gel processes for iridium-oxide pH sensors on flexible substrates.
In this paper, a new method for interconnecting free-space
micro-optoelectromechanical system (MOEMS) devices is
developed. The heterogeneous design and assembly concept is demonstrated by a pair of V-shape actuators and related
assembly mechanism, fabricated on a silicon-on-insulator (SOI) wafer. A two-channel free-space DWDM filter has
been assembled and characterized. The results show low insertion losses. The device architecture allows hybrid optical
system integration on a single platform. The assembled optical devices can be made of different materials, on different
substrates and/or with incompatible fabrication techniques. The integration platform provides potentials for realizing a
micro optical bench with equivalent optical performance that currently require bulk optics setups.
In this paper, we present design, modeling, fabrication, testing techniques and experimental verification for a bi-directional
thermal actuator. The actuation principle is based on the asymmetrical thermal expansion of pseudo-bimorph
microstructures due to the difference in the electrical resistance of two stacked poly-silicon layers. Bi-directional
actuation is achieved depending upon the application of currents on either the top or bottom layers. Various designs
were fabricated using the commercial foundry process PolyMUMPS and characterized with a reflective microscope and
an optical profiler. Previous demonstrated designs had a limited vertical displacement due to the mechanical limitation
imposed by the flexural lengths of the actuator arms. We proposed a new design allowing an increase of the maximum
displacement by 85% with the same input voltage of 7V. The flexure arm is incorporated in the top silicon layer such
that the torsion forces on the flexural arms are minimized. This enables larger deflection of the actuator arm without
significant increase in the temperature. Different device configurations have been designed and tested. The temperature
distributions on the actuator arms and displacements of the actuators at various conditions were analyzed using finite-element
analysis and verified experimentally. We will discuss the design configuration, testing techniques and practical
issues. The potential applications of the out-of-plane actuators include flow sensors, variable capacitors, resistive
sensors, optical switches and RF switches.
RF phase shifters find wide applications in telecommunications, satellite systems, personal wireless
communication systems, radar systems, tracking systems, and sensors. They have been conventionally
manufactured by semiconductor technologies which suffer from high insertion losses due to high RF series
resistances. They are expensive due to fabrication and assembly costs.
The RF MEMS phase shifters provide low insertion losses, low fabrication costs and high linearity compared
with the semiconductor ones. Furthermore, polymer materials have demonstrated low material costs and low
RF attenuations. In this work, we proposed to build RF MEMS phase shifters on polymer substrates. The
proposed devices were successfully manufactured and tested from DC to 26 GHz. Our experimental results
indicated more than 35 degrees phase shifts and low insertion losses.
Polymers have been considered as one of the most versatile materials in making optical devices for communication and sensor applications. They provide good optical transparency to form filters, lenses and many optical components with ease of fabrication. They are scalable and compatible in dimensions with requirements in optics and can be fabricated on inorganic substrates, such as silicon and quartz. Recent polymer synthesis also made great progresses on conductive and nonlinear polymers, opening opportunities for new applications. In this paper, we discussed hybrid-material integration of polymers on silicon-based microelectromechanical system (MEMS) devices. The motivation is to combine the advantages of demonstrated silicon-based MEMS actuators and excellent optical performance of polymers. We demonstrated the idea with a polymer-based out-of-plane Fabry-Perot filter that can be self-assembled by scratch drive actuators. We utilized a fabrication foundry service, MUMPS (Multi-User MEMS Process), to demonstrate the feasibility and flexibility of integration. The polysilicon, used as the structural material for construction of 3-D framework and actuators, has high absorption in the visible and near infrared ranges. Therefore, previous efforts using a polysilicon layer as optical interfaces suffer from high losses. We applied the organic compound materials on the silicon-based framework within the optical signal propagation path to form the optical interfaces. In this paper, we have shown low losses in the optical signal processing and feasibility of building a thin-film Fabry-Perot filter. We discussed the optical filter designs, mechanical design, actuation mechanism, fabrication issues, optical measurements, and results.
Optical communication and sensor industry face critical challenges in manufacturing for system integration. Due to the assembly complexity and integration platform variety, micro optical components require costly alignment and assembly procedures, in which many required manual efforts. Consequently, self-assembly device architectures have become a great interest and could provide major advantages over the conventional optical devices. In this paper, we discussed a self-assembly integration platform for micro optical components. To demonstrate the adaptability and flexibility of the proposed optical device architectures, we chose a commercially available MEMS fabrication foundry service - MUMPs (Multi-User MEMS Process). In this work, polysilicon layers of MUMPS are used as the 3-D structural material for construction of micro component framework and actuators. However, because the polysilicon has high absorption in the visible and near infrared wavelength ranges, it is not suitable for optical interaction. To demonstrate the required optical performance, hybrid integration of materials was proposed and implemented. Organic compound materials were applied on the silicon-based framework to form the required optical interfaces. Organic compounds provide good optical transparency, flexibility to form filters or lens and inexpensive manufacturing procedures. In this paper, we have demonstrated a micro optical filter integrated with self-assembly structures. We will discuss the self-assembly mechanism, optical filter designs, fabrication issues and results.
A new design for a high accuracy, 3-degree of freedom (DOF) MEMS manipulator is proposed. The 3-DOF robotic manipulator is to be used for biomedical applications such as cell probing, tissue sampling, neuron signal reading and drug delivery, in which high accuracy and repeatability of positioning is required. While sensing or imaging elements are not available in the integration with the manipulator to provide feedback for positioning, we investigated a calibration approach to minimize the positioning errors. In-plane and vertical MEMS thermal actuators are chosen to perform the required tasks. The modeling of the thermal actuators was first studied and the results match with experimental results. A calibration algorithm is implemented to allow the minimization of accumulated motion errors. The algorithm was successfully applied to the manipulator and results were obtained. A MATLAB script was written to simplify the calibration procedure. Problems faced in the design and potential solutions will be also discussed.