Tapered Side Wall Research Articles

Single-Cell Microarray Chip with Inverse-Tapered Wells to Maintain High Ratio of Cell Trapping.

A single-cell microarray (SCM) influenced by gravitational force is expected to be one of the simple methods in various fields such as DNA analysis and antibody production. After trapping the cells in the SCM chip, it is necessary to remove the liquid from the SCM to wash away the un-trapped cells on the chip and treat the reagents for analysis. The flow generated during this liquid exchange causes the trapped cells to drop out of conventional vertical wells. In this study, we propose an inverse-tapered well to keep trapped cells from escaping from the SCM. The wells with tapered side walls have a reduced force of flow toward the opening, which prevents trapped cells from escaping. The proposed SCM chip was fabricated using 3D photolithography and polydimethylsiloxane molding techniques. In the trapping experiment using HeLa cells, the cell residual rate increased more than two-fold for the SCM chip with the inverse-tapered well with a taper angle of 30° compared to that for the conventional vertical SCM chip after multiple rounds of liquid exchanges. The proposed well structure increases the number of trapped cells and decreases the cell dropout rate to improve the efficiency of cellular analysis.

Determination of lateral and vertical dielectrophoresis forces using tapered microelectrode array

The authors have introduced a method to generate and determine lateral and vertical dielectrophoresis forces simultaneously through a new configuration of microelectrodes arrays with tapered side wall profile. Two directions of motion are established based on obtaining a new crossover frequency, which they called as adjustment frequency (f adj) with the value between the crossover frequency of targeted and untargeted cells. The target particles could be particular biological cell in a mixture of cell and other particles or a mixture of cells with various physical and biological properties. The special design of microelectrodes arrays enables dielectrophoresis forces to manipulate and separate target species at two different locations via contactless technique by electrical driven but soft selective capture and sorting for higher efficiency and accuracy.

Development of Single Cell Array Using Micro Wells with Tapered Side Walls and Branch Microchannels

Development of Single Cell Array Using Micro Wells with Tapered Side Walls and Branch Microchannels

Tapered microelectrode array system for dielectrophoretically filtration: fabrication, characterization, and simulation study

This paper presents the fabrication, characterization, and simulation of microelectrode arrays system with tapered profile having an aluminum surface for dielectrophoresis (DEP)-based manipulation of particles. The proposed structure demonstrates more effective electric field gradient compared with its counterpart with untapered profile. Therefore, according to the asymmetric distribution of the electric field in the active region of microelectrode, it produces more effective particle manipulation. The tapered aluminum microelectrode array (TAMA) fabrication process uses a state-of-the-art technique in the formation of the resist’s taper profile. The performance of TAMA with various sidewall profile angles (5 deg to 90 deg) was analyzed through finite-element method numerical simulations to offer a better understanding of the origin of the sidewall profile effect. The ability of capturing and manipulating of the device was examined through modification of the Clausius–Mossotti factor and cross-over frequency (fx0). The fabricated system has been particularly implemented for filtration of particles with a desired diameter from a mixture of particles with three different diameters in an aqueous medium. The microelectrode system with tapered side wall profile offers a more efficient platform for particle manipulation and sensing applications compared with the conventional microelectrode systems.

Numerical Assessment of Compressive Deformation in Metal-Ceramic Multilayer Micro-Pillars

ABSTRACTA numerical study was undertaken to investigate the mechanical properties of metal-ceramic multilayer micro-pillars under compression. The model system contains alternating layers of aluminum (Al) and silicon carbide (SiC) above a thick silicon (Si) substrate. The finite element analyses show that the pillar deformed in a non-uniform manner under compression, especially when a tapered side wall was included in the model. The heterogeneous feature of the structure plays a significant role in influencing the apparent stress-strain response. The elastic property of the pillar compares favorably with the true composite modulus, but a large discrepancy was found in the plastic response. The difference in deformation behavior between homogeneous pillars and multilayer pillars, along with other geometric effects, were examined in detail.

190 nm excimer laser drilling of glass slices: Dependence of drilling rate and via hole shape on the diameter of the via hole

The authors have investigated the effect of the via hole diameter on the laser drilling rate of glass as well as the shape of the drilled via holes. An Ar–F2 based 193nm UV excimer laser was used in this study. The via holes with a diameter of 120μm showed a 7.5°–9° angled, tapered side wall, and the drilling rate was relatively constant at around 17μm∕s. For the smaller via holes with diameters ranging from 30–80μm, significantly different results were obtained due to laser reflection from the tapered side wall of the via hole leading to the drilling rate being slightly increased and via hole becoming conical in shape. For the smallest via holes with an entrance diameter of 10μm, the resulting hole showed a very high aspect ratio, with a funnel shaped via hole and a significantly reduced drilling rate.

Silicon template fabrication for imprint process with good demolding characteristics

Demolding force for thermal imprint process to polymethylmethacrylate (PMMA) film is examined by use of Si templates with various side wall profiles. Patterns with tapered side wall profile can be fabricated by control of etching conditions. Side wall profile can be smoothened by anisotropic etching by use of mixed solution of potassium hydroxide (KOH) solution and isopropyl-alcohol. It is confirmed that demolding force can be reduced when mold with tapered side wall pattern is used. Demolding force can be greatly reduced by KOH treatment. Especially, when the template with taper and smooth side wall patterns is used, demolding force is below our measurement system limit of 0.1 kgf. It is confirmed that the KOH treatment is very effective in order to reduce demolding force.

Submicron resolution of secondary radiation in LIGA polymethyl-methacrylate resist exposure

Secondary radiation during LIGA polymethyl-methacrylate (PMMA) resist exposure adversely affects feature definition, sidewall taper, and overall sidewall offset. Additionally, it can degrade the resist adjacent to the substrate, leading to the loss of free-standing features through undercutting during resist development or through mechanical failure of the degraded material. The source of this radiation includes photoelectrons, Auger electrons, fluorescence photons, etc. Sandia's Integrated Tiger Series (ITS), a coupled electron/photon Monte Carlo transport code, is used to compute dose profiles within 1 to 2 µm of the absorber edge and near the interface of the resist with a metallized substrate. The difficulty of submicron resolution requirement was overcome by solving a few local problems, having carefully designed micron-scale geometries. The results for a 10-keV x-ray photons source indicate a 2-µm dose transition region near the absorber edge, resulting from PMMA photoelectrons. This region leads to sidewall offset and to tapered sidewalls following resist development. The results also show a dose boundary layer of around 1 µm near the substrate interface due to electrons emitted from the substrate metallization layer. The maximum dose at the resist bottom under the absorber can be very high and can lead to feature loss during development. This model is also used to investigate resist doses resulting from multilayer substrate.

Low-Temperature Etching for Deep-Submicron Trilayer Resist

The effects of Cl2 addition to O2 plasma used for deep-submicron trilayer resist etching are investigated. The bottom-layer organic resist is etched using a low-temperature microwave plasma etcher. With O2+Cl2 etching gas, highly anisotropic etching is achieved at higher temperatures than with pure O2. Cl2 concentrations above 25% reduce resist selectivity relative to the SOG intermediate layer. Vertical 0.1-µm-wide resist patterns are achieved with O2+25% Cl2 at -60°C. Broadened resist patterns with tapered side walls are produced at lower temperatures and at higher Cl2 concentrations; this is thought to be caused by chlorine passivation and polymer deposition on the side walls.

A new supermagnetron plasma etcher remarkably suited for high performance etching

A new type of plasma etcher named a supermagnetron plasma etcher equipped with two parallel cathodes and an annular permanent magnet was developed. Using the supermagnetron plasma etcher, two kinds of experiments for the high rate etching of SiO2 and the highly uniform etching of photoresist and SiO2 under a stationary magnetic field were investigated. In the etchings of 6-in.-diam bare and patterned SiO2 wafers, high etch rates of 570 and 710 nm/min were obtained, respectively, using C2F6 gas of 7.5 mTorr. The etch selectivities of SiO2 to Si became as high as 6–15 using CHF3 gas at 3–6 mTorr. In a stationary magnetic field, the highly uniform etching of photoresist and SiO2 were also obtained using two types of supermagnetron plasma etchers. The etch uniformities depend on rf powers supplied to the upper and lower cathodes, gas pressure, and the position of a magnet, etc. High etch uniformities of ±5% were obtained without the rotation of a magnetic field in the etching of 3-in.-diam photoresist film and 6-in.-diam SiO2 at phase differences of rf voltages of about 180 and 250 degrees, respectively. Applying the CHF3 and O2 supermagnetron plasmas to submicron pattern etchings, SiO2 contact holes with tapered side walls and photoresist lines with vertical side walls were obtained, respectively.

Hydrodynamic modeling of some gas injection procedures in ladle metallurgy operations

Experimental studies of flows generated in a 0.30 scale water model of a 150 ton steelmaking ladle are reported. These were used to test the adequacy of a generalized two-dimensional computational scheme for predicting flows generated by fully submerged and partially submerged gas injection lances. The roles of turbulence models and grid configuration were assessed. Predictions for flow fields generated in a 150 ton steelworks ladle with and without tapered side walls, and with and without surface baffles around the rising plume were considered.