Biao Tang

Novel Driving Methods for Manipulating Oil Motion in Electrofluidic Display Pixels

By applying driving voltage schemes with different rising gradient and the same final voltage in an electrofluidic display device (EFD), several kinds of oil patterns have been generated. The results show that, in the initial stage of oil film splitting and contraction, driving voltage has a crucial influence on the microfluidic behavior and oil distribution in each pixel. Oil patterns significantly affect the pixel aperture and, ultimately, the reflectivity of the display panel. The oil pattern with fewer oil droplets has a higher aperture ratio and higher reflectivity. The observation that oil patterns can be controlled by varying driving schemes offers a new way of manipulating oil motion in EFD pixels.

Solid-phase sintering process and forced convective heat transfer performance of porous-structured micro-channels

Abstract A solid-phase sintering process for the low-cost fabrication of composite micro-channels was developed. Three kinds of composite micro-channels with metallic porous structures were designed. The sintering process was studied and optimized to obtain porous-structured micro-channels with high porosity. The flow resistance and heat transfer performance in the composite micro-channels were investigated. The composite micro-channels show acceptable flow resistance, significant enhancement of heat transfer and dramatic improvement of flow boiling stability, which indicates a promising prospect for the application in forced convective heat transfer.

Simplified dynamical model for optical response of electrofluidic displays

Abstract In this work we analyze the switching behavior of an electro-fluidic pixel in separate stages. For ‘on’ switching we consider the motion leading to oil film rupture (initiation stage), fast oil-dewetting and a slower droplet rearrangement stage. For ‘off’ switching we consider fast oil wetting and surface reforming to the flat (dark) state. A dynamic model derived from an overall energy balance analysis has been employed to describe the optical response inside an electrofluidic display (EFD) pixel for the oil dewetting and wetting stages. By comparison with the experimental electro–optic response data, the accuracy and shortcomings of this model can be illuminated. The optical response asymmetry between on and off-switching and optical response delay during the on-switching process are well described and explained. In addition, the liquid film reforming dynamics and electrohydrodynamic instability analysis are used to estimate the oil film rupture and film reforming times very well. This study provides a straightforward approach to describe the complicated electrofluidic switching dynamics inside an EFD pixel, which may guide the further optimization of EFD device design and driving schemes.

Coating and Patterning Functional Materials for Large Area Electrofluidic Arrays

Industrialization of electrofluidic devices requires both high performance coating laminates and efficient material utilization on large area substrates. Here we show that screen printing can be effectively used to provide homogeneous pin-hole free patterned amorphous fluoropolymer dielectric layers to provide both the insulating and fluidic reversibility required for devices. Subsequently, we over-coat photoresist using slit coating on this normally extremely hydrophobic layer. In this way, we are able to pattern the photoresist by conventional lithography to provide the chemical contrast required for liquids dosing by self-assembly and highly-reversible electrofluidic switching. Materials, interfacial chemistry, and processing all contribute to the provision of the required engineered substrate properties. Coating homogeneity as characterized by metrology and device performance data are used to validate the methodology, which is well-suited for transfer to high volume production in existing LCD cell-making facilities.

Well-Ordered Nanoporous Copper Fabricated by Dealloying Cu-Mn and its Characterizations

A nanoporous copper (NPC) sample with well-ordered porosity of 20 nm was fabricated by an electrochemical dealloying single-phase Cu0.4Mn0.6 with an external potential of-0.5 V (MSE). The electrochemical mechanism of the dealloying process on the Cu-Mn surface was studied by a liner sweep voltammetry experiment, and an optimized applied voltage for the Cu-Mn system was recommended. The properties of the monolithic NPC, including morphology, chemical composition, surface area and wettability were systematically characterized. The specific surface area around 11.86 m2/g of the as-dealloyed NPC was measured by BET-nitrogen method. The micro/nanoscale bi-continuous 3D porous structures of NPC not only increase the surface area, but also improve the wettability of NPC surface since the increase in surface roughness.

Large-Area and High-Throughput PDMS Microfluidic Chip Fabrication Assisted by Vacuum Airbag Laminator

One of the key fabrication steps of large-area microfluidic devices is the flexible-to-hard sheet alignment and pre-bonding. In this work, the vacuum airbag laminator (VAL) which is commonly used for liquid crystal display (LCD) production has been applied for large-area microfluidic device fabrication. A straightforward, efficient, and low-cost method has been achieved for 400 × 500 mm2 microfluidic device fabrication. VAL provides the advantages of precise alignment and lamination without bubbles. Thermal treatment has been applied to achieve strong PDMS–glass and PDMS–PDMS bonding with maximum breakup pressure of 739 kPa, which is comparable to interference-assisted thermal bonding method. The fabricated 152 × 152 mm2 microfluidic chip has been successfully applied for droplet generation and splitting.

16 Gray-scale driving schema based on DC-balance principle of electrophoretic display

The display quality improvement of electrophoretic paper largely depends on the increase in the number of grayscale, but it will make drive mode design complicated. The inhibition of residual driving voltage also becomes more difficult. This paper presents a new 16 gray-scale driving schema based on the DC-balance principle, improve the display quality of electrophoretic display (EPD). The display process is divided into DC rebalance phase and gray-scale drive phase. For every gray-scale conversion, pixel units make the original gray scale reach the basic gray scale via extreme white stage in the DC rebalance phase. Then a new gray-scale image is driven to show in the gray-scale driving phase. During the two sequential gray-scale conversions, voltages in the drive phase of the ith conversion and DC rebalance phase of the (i+1)th conversion always maintain DC balance, namely overall time of applying positive voltage in these two phases is equal to the overall time of applying negative voltage. The experimental results show that the proposed approach can effectively avoid the damage of driving electrode and display medium caused by the residual voltage accumulation, thus significantly extend the service life of the display.