Metastasis of cancer requires adhesion and migration of cells. The effect of chemokine gradient on prostate
cancer cells (PCC) is not well understood. A poly-dimethylsiloxane (PDMS) microfluidic device that
enables time-lapse study of cell migration is presented. Photolithography and soft lithography processes were
used to fabricate the PDMS devices from SU-8 molds. The device has two inlets, a cell reservoir and an outlet
channel with a depth of 100μm. The microfluidic device is configured to provide fluid mixing leading to a
gradient across the outlet channel. The inlets allow for introduction of different chemokines at different
concentrations and flow rates. The cell migration in the presence of chemokine gradient and flow rate can
thus be monitored in a time-lapse fashion. The gradient formations at different flow rates over different
lengths of time have been analyzed. Flow rates of 2, 3, 6, 8, 10, 20 μl/min at 5-minute intervals for over an
hour were monitored to determine optimum flow rates and times required to produce desired gradient
profiles. Results suggest that gradients formed at lower flow rates have less variation over time. Moreover,
lower flow rates do not affect cell movement making observation of cell migration towards gradients
possible. Higher flow rates have better gradient definition but cells tend to flow away with the fluid.
The analysis of cellular activity when exposed to polydimethylsiloxane (PDMS) is necessary as this material
has been used in various applications such as tissue engineering and microfluidic devices for cellular studies
due to the polymer's unique mechanical properties. In this particular study, we investigated the effects of
corona surface treated PDMS with different cross-linker ratios on cellular activities by analyzing prostate
cancer cell (PC-3) and vascular smooth muscle cell (VSMC) adhesion and proliferation. Both cell lines were
subjected to a thin PDMS layer immediately after and 24 hours after corona treatment. The results indicated
steady cell adhesion and proliferation rates for both smooth muscle and prostate cancer cells when seeded
onto PDMS 24 hours after corona surface treatment, but significantly less cell adhesion when seeded
immediately after activation and controls (PDMS without any treatment). These results would allow future
PC-3 and VSMC experiments to be performed in a PDMS environment that is not detrimental for adhesion
This paper discusses modeling, design, fabrication and characterization of an optical scanner based on cantilever-type
electrostatic zipping actuators. The electrostatic actuator has been designed to achieve high displacements for large
optical scanning angles at lower actuation voltages. The zipping actuators are fabricated using multi-layer polysilicon
foundry fabrication processes. The electrostatic force between the cantilever and the bottom electrode on the substrate
pulls the cantilever down. With a warped cantilever, the force closes the gap from the anchored end and gradually the
zipping effect actuates the entire cantilever. In our design, mechanical structures are arranged to avoid electrical shortcircuit.
With various annealing temperatures, the warped angles are controllable. The cantilever serves as a reflective
surface and the high out-of-plane displacement is used to steer a reflected laser beam for imaging and scanning
applications. In this paper we present the design considerations in electrostatic zipping actuator displacement and
control as well as the arrangement for optical scanning.
This paper discussed modeling, design, fabrication and characterization of a new cantilever-type electrostatic zipping
actuator. The actuator was designed to achieve high displacements and fabricated using multi-layer polysilicon foundry
fabrication process PolyMUMPS. The high out-of-plane displacement is to satisfy the requirements in specific optical
applications. In this paper we presented the design considerations in displacement, electrostatic forces and electrostatic
stability. The electrostatic force between the curved cantilever and the bottom electrode on the substrate pulls the
cantilever down. With a warped cantilever, the force closes the gap from the anchor end and gradually the zipping effect
actuates the entire cantilever without increasing the biasing voltages. Previous electrostatic zipper actuators require a
thin layer of dielectric material on top of the bottom electrode to prevent electrical shorting. They may have an issue
with electrical breakdown of the thin dielectric layer due to the film quality. We designed a new mechanical structure to
avoid the electrical shorting problem without a layer of dielectric material. Our analysis and experimental results
demonstrated that the proposed design can withstand high voltages without shorting and is capable of high deflection.
The vertical displacements of different device configurations were found ranging from 30.4μm to 450μm while the
actuation voltages varied in the range from 12V to 45.3V for complete actuation. The pull-in voltages for various
configurations were analyzed and presented.
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.
In this paper, we propose a new method to detect gastroesophageal reflux wirelessly. Based on passive telemetry using
inductive links, impedance of the refluxate can be determined. We have designed and fabricated planar coils integrated
with electrodes on flexible substrates using standard photolithography processes. The device can be implanted in the
esophagus using currently available clinical techniques. In vitro experiments were conducted by passing different acidic
or non-acidic solutions onto the implanted electrodes and measuring the signal amplitudes with an external receiver. Air,
drinking water and different concentrations of artificial stomach fluids were used to test the impedance sensor. System
configuration, device designs, fabrication processes and measurement results will be presented in this paper.
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 - <i>MUMPs</i> (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.