Electric Field Induced Self Assembly and Template Patterning of Polymer Microstructures

2001 ◽  
Vol 665 ◽  
Author(s):  
Cengiz S. Ozkan ◽  
Huajian Gao
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Indium Tin Oxide ◽  
Self Assembly ◽  
Polymer Surface ◽  
Dielectric Fluid ◽  
Force Microscopy ◽  
Polymer Microstructures ◽  
Polymer Optoelectronic Devices ◽  
Quartz Substrates

ABSTRACTWe have developed a method for fabricating polymer microstructures based on electric field induced self assembly and pattern formation. A dielectric fluid placed in between to conductive plates experiences a force in an applied electric field gradient across the plates, which can induce a diffusive surface instability and self construction of the fluid surface. This process is exploited for the fabrication of self assembled polymer microstructures as well as replicated patterns through the use of pre-patterned plates or electrodes. We have used silicon wafers and transparent ITO (Indium-Tin Oxide) coated quartz substrates to fabricate the capacitor structures. The bottom silicon plate is spin coated with a 100-200 nm thick polystyrene film. The ITO substrate was placed over the polymer surface at a distance to leave a thin air gap using spacers. For directed pattern transfer, patterned ITO substrates were used. The capacitor setup was heated above the glass transition temperature of the polymer and a voltage was applied across the plates (50-150 Volts), which induces electric fields on the order of 107–108 V/m. The capacitor structure was quenched to observe the structures using optical microscopy and atomic force microscopy. The method described can be used to fabricate a variety of structures in the micron and nanometer scales including bio-fluidic MEMS, polymer optoelectronic devices and patterned templates for nanolithography.

scholarly journals Self Assembly of Polymer Structures Induced by Electric Field

2003 ◽  
Vol 8 (2) ◽  
pp. 86-89 ◽  
Author(s):  
Mo Yang ◽  
Cengiz S. Ozkan ◽  
Huajian Gao
Keyword(s):  
Pattern Formation ◽  
Electric Field ◽  
Self Assembly ◽  
Applied Electric Field ◽  
Fem Simulation ◽  
Optoelectronic Devices ◽  
Dielectric Fluid ◽  
Gradient Distribution ◽  
Polymer Microstructures ◽  
Polymer Optoelectronic Devices

Amethod has been developed for fabricating polymer microstructures based on electric field induced self assembly and pattern formation. A dielectric fluid placed in between two conductive plates experience a force in an applied electric field gradient across the plates, which can induce a diffusive surface instability and self construction of the fluid surface. This process is exploited for the fabrication of self assembled polymer microstructures as well as replicated patterns through the use of pre-patterned plates or electrodes. FEM simulation is used to decide the minimum wavelength and electric gradient distribution of polymer structures. A variety of structures in the micron and nanometer scales including bio-fluidic MEMS, polymer optoelectronic devices can be fabricated using this method.

scholarly journals Electric Field Assisted Self-Assembly of Viruses into Colored Thin Films

Nanomaterials ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 1310 ◽  
Author(s):  
James J. Tronolone ◽  
Michael Orrill ◽  
Wonbin Song ◽  
Hyun Soo Kim ◽  
Byung Yang Lee ◽  
...  
Keyword(s):  
Electric Field ◽  
Self Assembly ◽  
Force Microscopy ◽  
Thin Film Coatings ◽  
Atomic Force ◽  
Three Phase ◽  
Constant Rate ◽  
Alignment Technique ◽  
Manufacturing Techniques ◽  
Blue Line

Filamentous viruses called M13 bacteriophages are promising materials for devices with thin film coatings because phages are functionalizable, and they can self-assemble into smectic helicoidal nanofilament structures. However, the existing “pulling” approach to align the nanofilaments is slow and limits potential commercialization of this technology. This study uses an applied electric field to rapidly align the nanostructures in a fixed droplet. The electric field reduces pinning of the three-phase contact line, allowing it to recede at a constant rate. Atomic force microscopy reveals that the resulting aligned structures resemble those produced via the pulling method. The field-assisted alignment results in concentric color bands quantified with image analysis of red, green, and blue line profiles. The alignment technique shown here could reduce self-assembly time from hours to minutes and lend itself to scalable manufacturing techniques such as inkjet printing.

Numerical Study of Dynamic Behavior of Dielectric Fluid Bubbles Within Diverging, External Electric Fields

2006 ◽  
Author(s):  
Matthew R. Pearson ◽  
Jamal Seyed-Yagoobi
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Numerical Study ◽  
Pool Boiling ◽  
Spherical Shape ◽  
Past Research ◽  
Bubble Surface ◽  
Uniform Electric Field ◽  
Dielectric Fluid ◽  
Uniform Field

Past research in the area of pool boiling within the presence of electric fields has generally focused on the case of uniform field intensity. Any numerical or analytical studies of the effect of non-uniform fields on the motion of bubbles within a dielectric liquid medium have assumed that the bubbles will retain their spherical shape rather than deform. These studies also ignore changes to the electrical field caused by the presence of the bubbles. However, these assumptions are not necessarily accurate as, even in the case of a nominally uniform electric field distribution, bubbles can exhibit considerable physical deformation and the field can become noticeably affected in the vicinity of the bubble. This study explores the effect that a non-uniform electric field can have on vapor bubbles of a dielectric fluid by modeling the physical deformation of the bubble and the alteration of the surrounding field. Numerical results show that the imbalance of electrical stresses at the bubble surface exerts a net dielectrophoretic force on the bubble, propelling the bubble to the vicinity of weakest electric field, thereby enhancing the separation of liquid and vapor phases during pool boiling. However, the proximity of the bubble to one of the electrodes can considerably alter the bubble trajectory due to an attractive force that arises from local distortions of the potential and electric fields. This phenomenon cannot be predicted if bubble deformation and field distortion effects are neglected.

scholarly journals Critical heat flux enhancement in microgravity conditions coupling microstructured surfaces and electrostatic field

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Alekos Ioannis Garivalis ◽  
Giacomo Manfredini ◽  
Giacomo Saccone ◽  
Paolo Di Marco ◽  
Artyom Kossolapov ◽  
...  
Keyword(s):  
Heat Flux ◽  
Electric Field ◽  
Critical Heat Flux ◽  
Electric Fields ◽  
Parabolic Flight ◽  
Dielectric Fluid ◽  
Two Phase ◽  
Microstructured Surfaces ◽  
Microgravity Conditions ◽  
Plain Surface

AbstractWe run pool boiling experiments with a dielectric fluid (FC-72) on Earth and on board an ESA parabolic flight aircraft able to cancel the effects of gravity, testing both highly wetting microstructured surfaces and plain surfaces and applying an external electric field that creates gravity-mimicking body forces. Our results reveal that microstructured surfaces, known to enhance the critical heat flux on Earth, are also useful in microgravity. An enhancement of the microgravity critical heat flux on a plain surface can also be obtained using the electric field. However, the best boiling performance is achieved when these techniques are used together. The effects created by microstructured surfaces and electric fields are synergistic. They enhance the critical heat flux in microgravity conditions up to 257 kW/m2, which is even higher than the value measured on Earth on a plain surface (i.e., 168 kW/m2). These results demonstrate the potential of this synergistic approach toward very compact and efficient two-phase heat transfer systems for microgravity applications.

Line Patterning with Microparticles at Different Positions in a Single Device Based on Negative Dielectrophoresis

2013 ◽  
Vol 25 (4) ◽  
pp. 650-656 ◽  
Author(s):  
Tomoyuki Yasukawa ◽  
◽  
Yusuke Yoshida ◽  
Hironobu Hatanaka ◽  
Fumio Mizutani
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Indium Tin Oxide ◽  
Strong Electric Field ◽  
Electric Signal ◽  
Electric Field Line ◽  
Peak Voltage ◽  
Ac Electric Field ◽  
Fluidic Device ◽  
Line Patterns

We report on control of line pattern positioning with particles fabricated by negative dielectrophoresis (n-DEP) using the applied intensity and phase of an AC electric field. Line patterns were fabricated in a microfluidic device consisting of upper conductive indium-tin-oxide (ITO) substrates and lower ITOinterdigitated microband array (IDA) electrodes used as the template. A 6-µm-diameter polystyrene particles suspension was introduced into the device between upper ITO and the bottom ITO-IDA substrate. An AC electric signal of a typically 20 peak-to-peak voltage and 1.0 MHz was then applied to upper ITO and bands on lower IDA, resulting in the formation of line patterns with low electric-field gradient regions. AC voltage was applied to bands A and B on lower IDA with the opposite phase and the same frequency and intensity. When the signal identical to band A was applied to upper ITO, particles were aligned above band A because relatively lower electric fields were produced in these regions. In contrast, the application of a signal identical to band B formed line patterns with particles aligned above band B due to the generation of a strong electric field between band A and upper ITO and the disappearance of the strong electric field between band B and upper ITO. The decrease in applied intensity to upper ITO shifted the accumulated position of particles to the center between bands A and B because of the balance of electric fields generated between band A or B and upper ITO. We thus fabricated line patterns with particles at desired positions in the fluidic device.

Electric field-controlled semiconductor nanorod assembly in solution: mechanistic insights from non-equilibrium molecular dynamics

2015 ◽  
Vol 93 (8) ◽  
pp. 888-890 ◽  
Author(s):  
Niall J. English
Keyword(s):  
Molecular Dynamics ◽  
Electric Field ◽  
Electric Fields ◽  
Self Assembly ◽  
Zero Field ◽  
Wide Range ◽  
Non Equilibrium Molecular Dynamics ◽  
Applied Fields ◽  
Preferential Alignment ◽  
Non Equilibrium

Non-equilibrium molecular dynamics (MD) of small, charged cadmium selenide nanorods have been carried out in the absence and presence of static applied electric fields. In the absence of applied fields, it was found that opposite dipolar alignment (antiferromagnetic) was achieved, along with self-assembly of the nanorods. However, in the case of induced electrophoresis in applied fields, the rods approached each other less readily, while at and above a field intensity of 0.05 V/Å, preferential alignment with the field was achieved for all rods, in contrast to the zero-field case. These results have implications for electric field-mediated control of nanorod assembly in solution, of key importance in a wide range of areas from photovoltaics to energy storage.

scholarly journals Photorefractive Effect in NLC Cells Caused by Anomalous Electrical Properties of ITO Electrodes

Crystals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 900
Author(s):  
Atefeh Habibpourmoghadam
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Indium Tin Oxide ◽  
Photorefractive Effect ◽  
Optical Power ◽  
Electrode Surfaces ◽  
Ito Film ◽  
Dc Electric Field ◽  
Spr Effect ◽  
Optically Induced

In a pure nematic liquid crystal (NLC) cell, optically induced charge carriers followed by transports in double border interfaces of orientant/LC and indium-tin-oxide (ITO)/orientant (or LC) can cause removal of screening of the static electric field inside the LC film. This is called surface photorefractive effect (SPR), which induces director field reorientation at a low DC electric field beyond the threshold at a reduced Fréedericksz transition and, as a result, a modulation of the LC effective refractive index. The studies conducted on the photoinduced opto-electrical responses in pure nematic LC cells biased with uniform static DC electric fields support the SPR effect (attributed to the photoelectric activation of the double interfaces). The SPR effect was further studied in LC cells with photoresponsive substrates, which act as a source of a bell-shaped electric field distribution in the LC film if no ITO electrode was employed. In an equipped cell with ITO, the photovoltaic electric field induces charge carrier redistribution in the ITO film, hence the SPR effect. This paper is aimed at highlighting all the evidences supporting ITO film as one of the fundamental sources of the SPR effect in pure NLC cells under the condition of applying low optical power and low DC voltage. An optically induced fringe electric field stemming from inhomogeneous photo-charge profiles near the electrode surfaces is expected in the LC film due to the semiconducting behavior of the ITO layer.

Effect of Substrate Type on the Electrical and Optical Properties of Cold-sputtered Indium Tin Oxide Films as a function of Post-deposition Heat Treatment

2010 ◽  
Vol 1256 ◽  
Author(s):  
Salil Joshi ◽  
Gregory W. Book ◽  
Rosario A. Gerhardt
Keyword(s):  
Tin Oxide ◽  
Indium Tin Oxide ◽  
Visible Region ◽  
Rf Sputtering ◽  
Heat Treatments ◽  
Visible Absorption ◽  
Force Microscopy ◽  
Quartz Substrates ◽  
Post Deposition ◽  
Ito Films

AbstractIndium Tin Oxide (ITO) films were deposited by RF sputtering onto glass and quartz substrates with no external heating. An ITO target containing 10 wt% SnO2 was used for the deposition in a Kurt Lesker PVD75 system, in an atmosphere of 50% O2 + 50% Ar. Post-deposition heat treatments were done on these coatings at 150°C, 300°C and 450°C in an atmosphere of commercial air or argon. The effects of these heat treatments on the microstructure and the properties of the films were evaluated using atomic force microscopy, resistivity measurements, and UV-visible absorption spectroscopy. The heat treatments were observed to significantly affect the properties such as transmittance in the visible region, optical band gap and the electrical resistivity of the films. The main differences are caused by the differences in thermal expansion coefficient of the substrates as compared to the sputtered ITO films.

Numerical Study of Dielectric Fluid Bubble Behavior Within Diverging External Electric Fields

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
Matthew R. Pearson ◽  
Jamal Seyed-Yagoobi
Keyword(s):  
Mathematical Model ◽  
Electric Field ◽  
Electric Fields ◽  
Numerical Study ◽  
Electrode Spacing ◽  
Small Scale ◽  
Arbitrary Distribution ◽  
Dielectric Fluid ◽  
Reciprocal Effect ◽  
Bubble Deformation

A three-dimensional mathematical model is presented that models bubble deformation of a dielectric fluid due to the presence of a nonuniform electric field and calculates the net dielectrophoretic force that is exerted by the electric field on the bubble. The study includes the development of a method of predicting the shape of a bubble based on the arbitrary distribution of stresses over its surface without requiring an axisymmetric configuration. The reciprocal effect of the bubble’s presence on the electric field is also incorporated into the model, and dimensional analysis is used to obtain a single key parameter that governs the bubble deformation phenomenon. Numerical implementation of the mathematical model shows that the bubble deformation can be significant. Furthermore, bubble deformation and electric field distortion can have significant effects on the dielectrophoretic behavior of bubbles in nonuniform fields, especially within small-scale devices where the bubble size and electrode spacing are similar in magnitude.

Wrinkling Poly(trimethylene 2,5-Furanoate) Free-standing Films: Nanostructure Formation and Physical Properties

2020 ◽  
Author(s):  
Michelina Soccio ◽  
Nadia Lotti ◽  
Andrea Munari ◽  
Esther Rebollar ◽  
Daniel E Martínez-Tong
Keyword(s):  
Irradiation Time ◽  
Polymer Surface ◽  
Laser Source ◽  
Free Standing ◽  
Force Microscopy ◽  
Nanostructure Formation ◽  
Physicochemical Changes ◽  
Angle Measurements ◽  
Atomic Force ◽  
Contact Angle Measurements

<p>Nanostructured wrinkles were developed on fully bio-based poly(trimethylene furanoate) (PTF) films by using the technique of Laser Induced Periodic Surface Structures (LIPSS). We investigated the effect of irradiation time on wrinkle formation using an UV pulsed laser source, at a fluence of 8 mJ/cm2. It was found that the pulse range between 600 and 4800 pulses allowed formation of periodic nanometric ripples. The nanostructured surface was studied using a combined macro- and nanoscale approach. We evaluated possible physicochemical changes taking place on the polymer surface after irradiation by infrared spectroscopy, contact angle measurements and atomic force microscopy. The macroscopic physicochemical properties of PTF showed almost no changes after nanostructure formation, differently from the results previously found for the terephthalic counterparts, as poly(ethyleneterephthalate), PET, and poly(trimethyleneterephthalate), PTT. The surface mechanical properties of the nanostructured PTF were found to be improved, as evidenced by nanomechanical force spectroscopy measurements. In particular, an increased Young’s modulus and higher stiffness for the nanostructured sample were measured. <br></p>

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