Papers by Keyword: SU-8

Abstract: In this paper, we study the electrowetting effect of superhydrophobic SU-8 film as the dielectric for Electrowetting-on-Dielectric (EWOD). The change of apparent contact angle (APCA) on superhydrophobic surface in electrowetting systems was measured and analyzed using a modified Lippmann-Yong equation. The variation of APCA between droplet and device surface under various DC voltage and AC voltage of different frequencies was fully experimented. The experimental results were in good agreement with the theoretical predictions. This study shows the potential of using superhydrophobic SU-8 film as the dielectric layer in high-performance EWOD devices.

Abstract: The GnF/SU-8 composites are new polymer matrix composites (PMCs) composed of graphite nanoflakes (GnFs) bound together by SU-8 photoresist. The PMCs therefore have excellent ultraviolet (UV) photopatternability and high electrical properties. In spite of the unique material properties of GnF/SU-8 composites, much still remains uncertain about their controllability in both UV photopatternability and electrical properties. Here, we investigate 7 kinds of GnF/SU-8 composites having different GnF concentrations of 5.0 to 25.0 wt.% to characterize the changes in the UV photopatternability (i.e., polymerized thickness and photopattern quality) and electrical conductivity of GnF/SU-8 composites caused by a variation in GnF concentration. The polymerized thickness of GnF/SU-8 composites is measured to be in the range of 4.06 to 23.99 μm, which is inversely proportional to GnF concentration and also directly proportional to UV dose (i.e., 345 to 3,450 mJ/cm²) because of the screening effect of GnF existed in the composites; the photopattern quality at the edge is in inverse proportion to GnF concentration. An increase in GnF concentration leads to a significant change in the electrical conductivity of GnF/SU-8 composites in a proportional way (up to 25.34 S/m). The GnF/SU-8 composites are expected to be widely used as UV photopatternable and electrically conductive PMCs for diverse engineering applications.

Abstract: In this paper, a new capacitive micromachined ultrasonic transducer (CMUT) is designed by using SU-8 material, and the theory of elastic thin plate is used to deduce the relationship between the pressure and capacitance of the structure. Simulation has been done about SU-8 CMUT by finite element method software ANSYS. The deformation of CMUT under acoustic pressure, the relationship between frequency, thickness and sensitivity, as well as the acoustic impedance and reflection coefficient of SU-8 material also have been studied through the simulation. The results turn out that SU-8 has the advantages of big dynamic range, high sensitivity and small acoustic impedance, so it has broad application in the ultrasonic field.

Abstract: An optimization method for fabricating 3D microneedle arrays with larger cone angles through backside exposure is demonstrated in this paper. A photo mask was designed to fabricate SU-8 microneedle based on diffraction of UV light. A circular hole diffraction was simulated with Matlab to obtain light intensity distribution. The simulation results show that the cone angles and surface profile can be adjusted by changing the thickness of substrate and exposure dose. Based on the simulation results, the microneedles with heights of 265 μm to 380 μm and cone angles in the range of 5.1° to 15.6° were fabricated by the backside exposure technology through one time UV lithography. Compared with previous approaches, the fabrication process in this paper takes advantages of simple, low cost and mass production.

Abstract: Laser micromachining technique was used in this work to produce two different microfluidic structure on three MEMS materials namely silicon, SU-8 photoresist and polydimethylsiloxane (PDMS). The operational parameters of the machine ablation effects on the materials, which are the laser energy, laser pulse rate and the laser size were also investigated. We found that this technique is capable to produce typical MEMS structure similar as being produced using conventional photolithography process.

Abstract: In this study, we developed a new method to fabricate microcoils with narrow and high aspect ratio coil lines using TSV and UV-LIGA technology in a SU-8 mold. The combination of SU-8 and TSV makes it possible to fabricate microstructures with high aspect ratio. TSV technology resolved the difficulties of electroplating with high aspect ratio. We designed and fabricated microcoils consisiting of coil lines with widths of 15μm and aspect ratio of 2.

Abstract: Micro- and nanotopography as well as the surface chemistry of biomaterials affect cell adhesion, proliferation and cell differentiation. Furthermore, the organization and localization of intracellular adhesion components such as the actin cytoskeleton are also altered dependent on the material surface topography. However, the detailed influence of the material micro-structure on cellular mechanisms on the molecular level is still unknown. This study is intended to elucidate such effects using regular pillar structures to characterize the modulation of cell responses like the regulation of voltage-sensitive calcium channels as well as signaling molecules in human osteoblasts. To analyze cell behavior on defined biomaterial surfaces, human osteoblastic MG 63 cells were cultured on geometrically micro textured titanium coated silicon wafers, as opposed to planar titanium references. Samples were fabricated by a photolithographic process using the negative tone resist SU 8 and sputter-coated with 100 nm titanium. Immunofluorescence staining and flow cytometry are used to detect the expression levels and the function of T type calcium channels. Knowledge about the biocomplexity of cell behavior dependent on topographical characteristics is of clinical relevance for the development of implant designs in tissue engineering.

Abstract: This paper investigated an novel wireless RF pressure sensor fabricated with SU-8 polymer. The sensor consists of an inductor (L) interconnected with pressure-variable capacitor (C) to form a LC resonant circuit. The fabricated devices is 4 × 3 mm² in size and houses 9 turns of Cu electro-plated coil with inductance of 100 nH. In this system, RF signal was transmitted from external antenna to the fabricated LC resonator. Then RF signal was changed as power of fabricated device via inductive coupling. The external antenna was modulated by resonant frequency of the LC resonator. By detecting this abrupt resonant frequency shift of the device, the pressure change of the device can be measured by wireless method.

Abstract: A precisely rectilinear electrothermal actuator integrated with highly thermally expandable micromachined composites of SU-8 and silicon is presented. The actuator is capable of producing a maximum output rectilinear displacement of 42 μm with an estimated blocked force of up to 61 mN. The actuator operates at a low temperature rise of less than 266 °C and at input voltage of less than 15 V. Thermal time constant of the actuator is measured to be less than 3 ms. Such a powerful and power-efficient actuator could benefits future devices in optical MEMS.

Abstract: In this paper, we describe the design, simulation of a novel check valve suitable for potentially embedding in polymeric microfluidic devices such as micro-pumps. Using SU-8 as functional material, the check valve can be fabricated by MEMS technology, such as, UV-LIGA and electroforming. The check valve mainly consists of two structural layers: inlet layer and valve membrane layer. From simulation, the maximum deflection of check valve membrane is 116μm under pressure of 2000Pa, and the maximum stress is 18.1MPa. We consider the fit thickness of valve membrane is 20μm. Simulation results demonstrate that this novel check valve can be potentially integrated in many micro-pumps and other lab-on-a-chip systems.