Name: procedure for the transfer of polymer films onto porous substrates with minimized defects
Uploaded: 2019-06-22T14:00:00
Description: Watch this Scientific Journal Video about Procedure for the Transfer of Polymer Films Onto Porous Substrates with Minimized Defects at JoVE.com

This work was supported as part of the Advanced Materials for Energy-Water Systems (AMEWS) Center, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences. We gratefully acknowledge helpful discussions with Mark Stoykovich and Paul Nealey.

1. Fabrication of the transfer tool and drain chamber system
<ol>
	<li>Attached (Supplementary Files 1, 2) is the engineering drawing for the drain chamber assembly consisting of two parts: top and bottom. Model this device according to the specifications of the desired system (e.g., the outer diameter of the receiving substrate) and export as an STL file for 3D printing.</li>
	<li>For the top part, utilize a filament printer of choice and print in the lowest resolution possible, inclu...

<ol>
	<li>Shah, A., Torres, P., Tscharner, R., Wyrsch, N., Keppner, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Photovoltaic+technology:+the+case+for+thin-film+solar+cells.">Photovoltaic technology: the case for thin-film solar cells.</a> Science. 285 (5428), 692-698 (1999).</li><li>Kim, T. H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Full-colour+quantum+dot+displays+fabricated+by+transfer+printing.">Full-colour quantum dot displays fabricated by transfer printing.</a> Nat. Photon. 5 (3), 176 (2011).</li><li>Nomura, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Room-temperature+fabrication+of+transparent+flexible+thin-film+transistors+using+amorphous+oxide+semiconductors.">Room-temperature fabrication of transparent flexible thin-film transistors using amorphous oxide semiconductors.</a> Nature. 432 (7016), 488 (2004).</li><li>Pirkle, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+effect+of+chemical+residues+on+the+physical+and+electrical+properties+of+chemical+vapor+deposited+graphene+transferred+to+SiO2.">The effect of chemical residues on the physical and electrical properties of chemical vapor deposited graphene transferred to SiO2.</a> Applied Physics Letters. 99 (12), 122108-122110 (2011).</li><li>Chae, S. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthesis+of+large-area+graphene+layers+on+poly-nickel+substrate+by+chemical+vapor+deposition:+wrinkle+formation.">Synthesis of large-area graphene layers on poly-nickel substrate by chemical vapor deposition: wrinkle formation.</a> Advanced Materials. 21 (22), 2328-2333 (2009).</li><li>Zhu, W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Structure+and+electronic+transport+in+graphene+wrinkles.">Structure and electronic transport in graphene wrinkles.</a> Nano Letters. 12 (7), 3431-3436 (2012).</li><li>Paronyan, T. M., Pigos, E. M., Chen, G., Harutyunyan, A. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Formation+of+ripples+in+graphene+as+a+result+of+interfacial+instabilities.">Formation of ripples in graphene as a result of interfacial instabilities.</a> ACS Nano. 5 (12), 9619-9627 (2011).</li><li>Stadermann, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fabrication+of+large-area+free-standing+ultrathin+polymer+films.">Fabrication of large-area free-standing ultrathin polymer films.</a> Journal of Visualized Experiments : JoVE. (100), e52832 (2015).</li><li>Zhou, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fabrication+of+Nanoporous+Alumina+Ultrafiltration+Membrane+with+Tunable+Pore+Size+Using+Block+Copolymer+Templates.">Fabrication of Nanoporous Alumina Ultrafiltration Membrane with Tunable Pore Size Using Block Copolymer Templates.</a> Advanced Functional Materials. 27 (34), 1701756 (2017).</li><li>Meitl, M. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transfer+printing+by+kinetic+control+of+adhesion+to+an+elastomeric+stamp.">Transfer printing by kinetic control of adhesion to an elastomeric stamp.</a> Nature Materials. 5 (1), 33 (2006).</li><li>Suk, J. W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transfer+of+CVD-grown+monolayer+graphene+onto+arbitrary+substrates.">Transfer of CVD-grown monolayer graphene onto arbitrary substrates.</a> ACS Nano. 5 (9), 6916-6924 (2011).</li><li>Chen, Y., Gong, X. L., Gai, J. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Progress+and+Challenges+in+Transfer+of+Large-Area+Graphene+Films.">Progress and Challenges in Transfer of Large-Area Graphene Films.</a> Advanced Science. 3 (8), 1500343 (2016).</li></ol>

While many of the steps listed in this protocol are crucial for the success of the thin film transfer, the nature of the custom-designed 3D printed drain chamber allows for broad flexibility, according to the user's specific requirements. For example, if the receiver substrate has a larger diameter than the 25-mm-diameter AAO discs utilized in this study, the drain chamber can be appropriately modified to fit the new specifications. However, there are certain aspects of the protocol that are necessary to ensure effective...

Thin film and nanomembrane-based devices have recently garnered wide interest due to their potential use in a broad range of applications, ranging from flexible photovoltaics and photonics, foldable displays, and wearable electronics1,2,3. A requirement for the fabrication of these various types of devices is the transfer of thin films to the surfaces of arbitrary substrates, which remains challenging due to the fragility of these films and the frequent production of macroscale defect structures, such as wrinkles, cracks, and tears, within the films after transfer4,5,6,7. Manual transfer by hand, tweezers, and wire loops are common methods of thin film transfer, but inevitably result in structural incongruities and plastic deformation8,9. Various types of thin film transfer methodologies have been explored such as: 1) polydimethylsiloxane (PDMS) stamp transfer, which involves the use of an elastomeric stamp to obtain the thin film from the donor substrate and subsequently transfer to the receiving substrate10, and 2) sacrificial layer transfer11, in which an etchant is used to selectively dissolve a sacrificial layer between the support substrate and the thin film, thereby lifting off the thin film. However, these techniques alone do not necessarily allow for thin film transfer without incurring damage to or defect formation within the thin films12.
Here, we present a novel, low-cost, and generalizable facile method based on sacrificial layer lift-off and meniscus-guided transfer within a custom-designed, 3D-printed drain chamber system, to mechanically place block copolymer (BCP) thin films onto the centers of porous substrates such as anodized aluminum oxide (AAO) discs with little-to-no incurred macroscale defect structures, such as wrinkles, tears, and cracks. In the present context, these transferred thin films can then be used as devices in water filtration studies, potentially after sequential infiltration synthesis (SIS) processing9. Image analysis of transferred films obtained from optical microscopy show that the meniscus-guided, drain-chamber system provides smooth, robust, and wrinkle-free samples. In addition, the images also demonstrate the system&#39;s ability to reliably place the thin film membranes onto the centers of the receiving substrates. Our results have significant implications for any type of device application requiring the transfer of thin film structures onto the surfaces of arbitrary porous substrates.

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			<td height="42" style="height:42px;width:264px;">35% sodium polyacrylic acid solution</td>
			<td style="width:73px;">Sigma Aldrich</td>
			<td style="width:123px;">9003-01-4&#160;&#160;</td>
			<td style="width:171px;"></td>
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			<td height="21" style="height:21px;width:264px;">Amicon Stirred Cell model 8010 10mL</td>
			<td style="width:73px;">Millipore</td>
			<td style="width:123px;">5121</td>
			<td></td>
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			<td height="42" style="height:42px;width:264px;">Anodized aluminum oxide, 0.2u thickness, 25mm diameter</td>
			<td style="width:73px;">Sigma Aldrich</td>
			<td style="width:123px;">WHA68096022</td>
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		<tr height="21">
			<td height="21" style="height:21px;width:264px;">o ring neoprene 117</td>
			<td style="width:73px;">Grainger</td>
			<td>1BUV7</td>
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			<td height="21" style="height:21px;width:264px;">Objet500 Connex3 3D Printer</td>
			<td style="width:73px;">Stratasys</td>
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			<td height="21" style="height:21px;width:264px;">Onshape 3D software</td>
			<td style="width:73px;">onshape</td>
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			<td height="21" style="height:21px;width:264px;">Polylactic acid filament</td>
			<td style="width:73px;">Ultimaker</td>
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			<td></td>
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		<tr height="21">
			<td height="21" style="height:21px;width:264px;">ultimaker3 3d filament printer</td>
			<td style="width:73px;">Ultimaker</td>
			<td style="width:123px;"></td>
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		<tr height="21">
			<td height="21" style="height:21px;width:264px;">Vero Family printable materials</td>
			<td style="width:73px;">Stratasys</td>
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procedure for the transfer of polymer films onto porous substrates with minimized defects

The fabrication of devices containing thin film composite membranes necessitates the transfer of these films onto the surfaces of arbitrary support substrates. Accomplishing this transfer in a highly controlled, mechanized, and reproducible manner can eliminate the creation of macroscale defect structures (e.g., tears, cracks, and wrinkles) within the thin film that compromise device performance and the usable area per sample. Here, we describe a general protocol for the highly controlled and mechanized transfer of a polymeric thin film onto an arbitrary porous support substrate for eventual use as a water filtration membrane device. Specifically, we fabricate a block copolymer (BCP) thin film on top of a sacrificial, water-soluble poly(acrylic acid) (PAA) layer and silicon wafer substrate. We then utilize a custom-designed, 3D-printed transfer tool and drain chamber system to deposit, lift-off, and transfer the BCP thin film onto the center of a porous anodized aluminum oxide (AAO) support disc. The transferred BCP thin film is shown to be consistently placed onto the center of the support surface due to the guidance of the meniscus formed between the water and the 3D-printed plastic drain chamber. We also compare our mechanized transfer-processed thin films to those that have been transferred by hand with the use of tweezers. Optical inspection and image analysis of the transferred thin films from the mechanized process confirm that little-to-no macroscale inhomogeneities or plastic deformations are produced, as compared to the multitude of tears and wrinkles produced from manual transfer by hand. Our results suggest that the proposed strategy for thin film transfer can reduce defects when compared to other methods across many systems and applications.

The BCP membrane samples were fabricated according to the previously described procedure9. The samples were placed onto the lip of the loading arm of the 3D-printed transfer tool (Figure 1, left) and subsequently lowered, with a laboratory jack, onto the entrance ramp of the 3D-printed drain chamber tool (Figure 1, right). A sacrificial layer of poly(acrylic acid) (PAA) between the BCP membrane and underly...

Watch this Scientific Journal Video about Procedure for the Transfer of Polymer Films Onto Porous Substrates with Minimized Defects at JoVE.com

Procedure for the Transfer of Polymer Films Onto Porous Substrates with Minimized Defects

We present a procedure for highly controlled and wrinkle-free transfer of block copolymer thin films onto porous support substrates using a 3D-printed drain chamber. The drain chamber design is of general relevance to all procedures involving transfer of macromolecular films onto porous substrates, which is normally done by hand in an irreproducible fashion.

The fabrication of devices containing thin film composite membranes necessitates the transfer of these films onto the surfaces of arbitrary support ...

To study polymer thin films in membrane applications, materials must be transferred from a polished, smooth substrate to porous substrates in a fashion that does not fold, wrinkle, tear, or plastically deform the film. This video describes a 3D printable drain chamber designed to achieve this aim and concerns steps four through six in the process flow shown here. Samples used in this work consist of silicon wafer substrates into which are spin coated a stack of water soluble polyacrylic acid followed by a random copolymer mat and a polystyrene block polymethyl methacrylate block copolymer.The aim of steps four through six is to transfer this pore-forming block copolymer from the silicon wafer onto a porous anodized aluminum oxide membrane to enable subsequent transformation into a functional filtration device. The drain chamber consists of a top ramp that enables the introduction of the polymer film stack and a bottom portion which holds the porous substrate and deionized water. The top part is printed from PLA from a filament printer, and the bottom portion was printed from an inkjet 3D printer.A sample transfer tool is also printed from PLA using the filament printer. The first part attaches to a laboratory jack so the sample can be raised and lowered smoothly and without vibrations from hand movements. The second part holds the BCP wafer piece in place.With that, the transfer process can begin. First, the BCP tool is assembled. The clamp portion is threaded so a screw can secure it to the lab jack.The anodized aluminum oxide substrate is then placed inside of the bottom portion of the drain chamber using forceps. Next, a rubber O-ring is inserted to ensure a waterproof seal. The ramp portion of the drain chamber is screwed on tightly.Last, clear vinyl tubing is attached to the spout at the bottom portion of the drain chamber and the other end to the syringe which is inside of a syringe pump to be able to control the drainage rate. Next, the silicon wafer with the polymer stack is placed on the transfer tool, and the drain chamber is also filled with deionized water. The silicon wafer is then lowered slowly into the water, which causes the polyacrylic acid layer to begin to dissolve.This dissolution delaminates the polymer film from the silicon wafer leaving it to float on the water surface. The transfer tool is next removed, and the draining is activated by starting the syringe pump. The water is suctioned through the aluminum oxide substrate and out of the chamber by the pump.Shown here is the draining taking place at a rate of one milliliter per minute. The angle of the ramp and design of the chamber directs the polymer film towards the center of the cylinder. Here, the membrane and the water level have reached the cylindrical body of the device, creating a more prominent meniscus, which holds the membrane taut and centered as it is lower to the underlying, anodized aluminum oxide membrane.Once the water is drained and the polymer is in contact with the membrane, the chamber can be unscrewed to allow the remaining water to evaporate. The total process, including setup and water draining, takes about 15 minutes, but this time can be shortened by increasing the draining rate and by constructing the chamber to require a smaller water volume. Shown here are films prepared by directly scooping them off of a water bath surface using the porous membrane.The tearing of the membrane and the placement off center are evident. The distance of the membrane center to the substrate center is shown on the right for various placed membranes. Here we see the improvement in reproducibility utilizing the drain chamber.The intact films are evident, and the distance of membrane center to substrate center is shown to be minimized. The drain chamber has reduced the chance of film tearing and folding over the manual method. A clean laboratory environment free from dust will limit incidental contamination.This method for thin film membrane transfer definitively reduces the damage done to the membrane and improves the accuracy and reproducibility of its placement on the substrate. By removing the difficult task of manipulating thin films on the water surface by hand, modifications to the basic drain chamber design can allow for the implementation of different polymer sample sizes and porous substrate types.

procedure-for-transfer-polymer-films-onto-porous-substrates-with

Research

JoVE Journal

Engineering

Micropunching Lithography for Generating Micro- and Submicron-patterns on Polymer Substrates

Conducting polymers have attracted great attention since the discovery of high conductivity in doped polyacetylene in 19771. They offer the advantages of low weight, easy tailoring of properties and a wide spectrum of applications2,3. Due to sensitivity of conducting polymers to environmental conditions (e.g., air, oxygen, moisture, high temperature and chemical solutions), lithographic techniques present significant technical challenges when working with these materials4. For example, current photolithographic methods, such as ultra-violet (UV), are unsuitable for patterning the conducting polymers due to the involvement of wet and/or dry etching processes in these methods. In addition, current micro/nanosystems mainly have a planar form5,6. One layer of structures is built on the top surfaces of another layer of fabricated features. Multiple layers of these structures are stacked together to form numerous devices on a common substrate. The sidewall surfaces of the microstructures have not been used in constructing devices. On the other hand, sidewall patterns could be used, for example, to build 3-D circuits, modify fluidic channels and direct horizontal growth of nanowires and nanotubes.
A macropunching method has been applied in the manufacturing industry to create macropatterns in a sheet metal for over a hundred years. Motivated by this approach, we have developed a micropunching lithography method (MPL) to overcome the obstacles of patterning conducting polymers and generating sidewall patterns. Like the macropunching method, the MPL also includes two operations (Fig. 1): (i) cutting; and (ii) drawing. The "cutting" operation was applied to pattern three conducting polymers4, polypyrrole (PPy), Poly(3,4-ethylenedioxythiophen)-poly(4-styrenesulphonate) (PEDOT) and polyaniline (PANI). It was also employed to create Al microstructures7. The fabricated microstructures of conducting polymers have been used as humidity8, chemical8, and glucose sensors9. Combined microstructures of Al and conducting polymers have been employed to fabricate capacitors and various heterojunctions9,10,11. The "cutting" operation was also applied to generate submicron-patterns, such as 100- and 500-nm-wide PPy lines as well as 100-nm-wide Au wires. The "drawing" operation was employed for two applications: (i) produce Au sidewall patterns on high density polyethylene (HDPE) channels which could be used for building 3D microsystems12,13,14, and (ii) fabricate polydimethylsiloxane (PDMS) micropillars on HDPE substrates to increase the contact angle of the channel15.

A micropunching lithography approach is developed to generate micro- and submicron-patterns on top, sidewall and bottom surfaces of polymer substrates. It overcomes the obstacles of patterning conducting polymers and generating sidewall patterns. This method allows rapid fabrication of multiple features and is free of aggressive chemistry.

Conducting polymers have attracted great attention since the discovery of high conductivity in doped polyacetylene in 19771. They offer the advantages of ...

Integrating a Triplet-triplet Annihilation Up-conversion System to Enhance Dye-sensitized Solar Cell Response to Sub-bandgap Light

The poor response of dye-sensitized solar cells (DSCs) to red and infrared light is a significant impediment to the realization of higher photocurrents and hence higher efficiencies. Photon up-conversion by way of triplet-triplet annihilation (TTA-UC) is an attractive technique for using these otherwise wasted low energy photons to produce photocurrent, while not interfering with the photoanodic performance in a deleterious manner. Further to this, TTA-UC has a number of features, distinct from other reported photon up-conversion technologies, which renders it particularly suitable for coupling with DSC technology. In this work, a proven high performance TTA-UC system, comprising a palladium porphyrin sensitizer and rubrene emitter, is combined with a high performance DSC (utilizing the organic dye D149) in an integrated device. The device shows an enhanced response to sub-bandgap light over the absorption range of the TTA-UC sub-unit resulting in the highest figure of merit for up-conversion assisted DSC performance to date.

An integrated device, incorporating a dye-sensitized solar cell and triplet-triplet annihilation up-conversion unit was produced, affording enhanced light harvesting, from a wider section of the solar spectrum. Under modest irradiation levels a significantly enhanced response to low energy photons was demonstrated, yielding a record figure of merit for dye-sensitized solar cells.

The poor response of dye-sensitized solar cells (DSCs) to red and infrared light is a significant impediment to the realization of higher photocurrents ...

SSVEP-based Experimental Procedure for Brain-Robot Interaction with Humanoid Robots

Brain-Robot Interaction (BRI), which provides an innovative communication pathway between human and a robotic device via brain signals, is prospective in helping the disabled in their daily lives. The overall goal of our method is to establish an SSVEP-based experimental procedure by integrating multiple software programs, such as OpenViBE, Choregraph, and Central software as well as user developed programs written in C++ and MATLAB, to enable the study of brain-robot interaction with humanoid robots.
This is achieved by first placing EEG electrodes on a human subject to measure the brain responses through an EEG data acquisition system. A user interface is used to elicit SSVEP responses and to display video feedback in the closed-loop control experiments. The second step is to record the EEG signals of first-time subjects, to analyze their SSVEP features offline, and to train the classifier for each subject. Next, the Online Signal Processor and the Robot Controller are configured for the online control of a humanoid robot. As the final step, the subject completes three specific closed-loop control experiments within different environments to evaluate the brain-robot interaction performance.
The advantage of this approach is its reliability and flexibility because it is developed by integrating multiple software programs. The results show that using this approach, the subject is capable of interacting with the humanoid robot via brain signals. This allows the mind-controlled humanoid robot to perform typical tasks that are popular in robotic research and are helpful in assisting the disabled.

The overall goal of this method is to establish an SSVEP-based experimental procedure by integrating multiple software programs to enable the study of brain-robot interaction with humanoid robots, which is prospective in assisting the sick and elderly as well as performing unsanitary or dangerous jobs.

Brain-Robot Interaction (BRI), which provides an innovative communication pathway between human and a robotic device via brain signals, is prospective in ...

Electroactive Polymer Nanoparticles Exhibiting Photothermal Properties

A method for the synthesis of electroactive polymers is demonstrated, starting with the synthesis of extended conjugation monomers using a three-step process that finishes with Negishi coupling. Negishi coupling is a cross-coupling process in which a chemical precursor is first lithiated, followed by transmetallation with ZnCl2. The resultant organozinc compound can be coupled to a dibrominated aromatic precursor to give the conjugated monomer. Polymer films can be prepared via electropolymerization of the monomer and characterized using cyclic voltammetry and ultraviolet-visible-near infrared (UV-Vis-NIR) spectroscopy. Nanoparticles (NPs) are prepared via emulsion polymerization of the monomer using a two-surfactant system to yield an aqueous dispersion of the polymer NPs. The NPs are characterized using dynamic light scattering, electron microscopy, and UV-Vis-NIR-spectroscopy. Cytocompatibility of NPs is investigated using the cell viability assay. Finally, the NP suspensions are irradiated with a NIR laser to determine their effectiveness as potential materials for photothermal therapy (PTT).

A protocol is presented for the synthesis and preparation of nanoparticles consisting of electroactive polymers.

A method for the synthesis of electroactive polymers is demonstrated, starting with the synthesis of extended conjugation monomers using a three-step ...

Fabrication of Polymer Microspheres for Optical Resonator and Laser Applications

This paper describes three methods of preparing fluorescent microspheres comprising &#960;-conjugated or non-conjugated polymers: vapor diffusion, interface precipitation, and mini-emulsion. In all methods, well-defined, micrometer-sized spheres are obtained from a self-assembling process in solution. The vapor diffusion method can result in spheres with the highest sphericity and surface smoothness, yet the types of the polymers able to form these spheres are limited. On the other hand, in the mini-emulsion method, microspheres can be made from various types of polymers, even from highly crystalline polymers with coplanar, &#960;-conjugated backbones. The photoluminescent (PL) properties from single isolated microspheres are unusual: the PL is confined inside the spheres, propagates at the circumference of the spheres via the total internal reflection at the polymer/air interface, and self-interferes to show sharp and periodic resonant PL lines. These resonating modes are so-called "whispering gallery modes" (WGMs). This work demonstrates how to measure WGM PL from single isolated spheres using the micro-photoluminescence (&#181;-PL) technique. In this technique, a focused laser beam irradiates a single microsphere, and the luminescence is detected by a spectrometer. A micromanipulation technique is then used to connect the microspheres one by one and to demonstrate the intersphere PL propagation and color conversion from coupled microspheres upon excitation at the perimeter of one sphere and detection of PL from the other microsphere. These techniques, &#181;-PL and micromanipulation, are useful for experiments on micro-optic application using polymer materials.

Protocols for the synthesis of microspheres from polymers, the manipulation of microspheres, and micro-photoluminescence measurements are presented.

This paper describes three methods of preparing fluorescent microspheres comprising &#960;-conjugated or non-conjugated polymers: vapor diffusion, ...

Fabrication of Ultra-thin Color Films with Highly Absorbing Media Using Oblique Angle Deposition

Ultra-thin film structures have been studied extensively for use as optical coatings, but performance and fabrication challenges remain.&#160; We present an advanced method for fabricating ultra-thin color films with improved characteristics. The proposed process addresses several fabrication issues, including large area processing. Specifically, the protocol describes a process for fabricating ultra-thin color films using an electron beam evaporator for oblique angle deposition of germanium (Ge) and gold (Au) on silicon (Si) substrates.&#160; Film porosity produced by the oblique angle deposition induces color changes in the ultra-thin film. The degree of color change depends on factors such as deposition angle and film thickness. Fabricated samples of the ultra-thin color films showed improved color tunability and color purity. In addition, the measured reflectance of the fabricated samples was converted into chromatic values and analyzed in terms of color. Our ultra-thin film fabricating method is expected to be used for various ultra-thin film applications such as flexible color electrodes, thin film solar cells, and optical filters. Also, the process developed here for analyzing the color of the fabricated samples is broadly useful for studying various color structures.

We present a detailed method for fabricating ultra-thin color films with improved characteristics for optical coatings. The oblique angle deposition technique using an electron beam evaporator allows improved color tunability and purity. Fabricated films of Ge and Au on Si substrates were analyzed by reflectance measurements and color information conversion.

Ultra-thin film structures have been studied extensively for use as optical coatings, but performance and fabrication challenges remain.&#160; We present ...

Preparation of Large-area Vertical 2D Crystal Hetero-structures Through the Sulfurization of Transition Metal Films for Device Fabrication

We have demonstrated that through the sulfurization of transition metal films such as molybdenum (Mo) and tungsten (W), large-area and uniform transition metal dichalcogenides (TMDs) MoS2 and WS2 can be prepared on sapphire substrates. By controlling the metal film thicknesses, good layer number controllability, down to a single layer of TMDs, can be obtained using this growth technique. Based on the results obtained from the Mo film sulfurized under the sulfur deficient condition, there are two mechanisms of (a) planar MoS2 growth and (b) Mo oxide segregation observed during the sulfurization procedure. When the background sulfur is sufficient, planar TMD growth is the dominant growth mechanism, which will result in a uniform MoS2 film after the sulfurization procedure. If the background sulfur is deficient, Mo oxide segregation will be the dominant growth mechanism at the initial stage of the sulfurization procedure. In this case, the sample with Mo oxide clusters covered with few-layer MoS2 will be obtained. After sequential Mo deposition/sulfurization and W deposition/sulfurization procedures, vertical WS2/MoS2 hetero-structures are established using this growth technique. Raman peaks corresponding to WS2 and MoS2, respectively, and the identical layer number of the hetero-structure with the summation of individual 2D materials have confirmed the successful establishment of the vertical 2D crystal hetero-structure. After transferring the WS2/MoS2 film onto a SiO2/Si substrate with pre-patterned source/drain electrodes, a bottom-gate transistor is fabricated. Compared with the transistor with only MoS2 channels, the higher drain currents of the device with the WS2/MoS2 hetero-structure have exhibited that with the introduction of 2D crystal hetero-structures, superior device performance can be obtained. The results have revealed the potential of this growth technique for the practical application of 2D crystals.

Through the sulfurization of pre-deposited transition metals, large-area and vertical 2D crystal hetero-structures can be fabricated. The film transferring and device fabrication procedures are also demonstrated in this report.

We have demonstrated that through the sulfurization of transition metal films such as molybdenum (Mo) and tungsten (W), large-area and uniform transition ...

Fabricating Reactive Surfaces with Brush-like and Crosslinked Films of Azlactone-Functionalized Block Co-Polymers

In this paper, fabrication methods that generate novel surfaces using the azlactone-based block co-polymer, poly (glycidyl methacrylate)-block-poly (vinyl dimethyl azlactone) (PGMA-b-PVDMA), are presented. Due to the high reactivity of azlactone groups towards amine, thiol, and hydroxyl groups, PGMA-b-PVDMA surfaces can be modified with secondary molecules to create chemically or biologically functionalized interfaces for a variety of applications. Previous reports of patterned PGMA-b-PVDMA interfaces have used traditional top-down patterning techniques that generate non-uniform films and poorly controlled background chemistries. Here, we describe customized patterning techniques that enable precise deposition of highly uniform PGMA-b-PVDMA films in backgrounds that are chemically inert or that have biomolecule-repellent properties. Importantly, these methods are designed to deposit PGMA-b-PVDMA films in a manner that completely preserves azlactone functionality through each processing step. Patterned films show well-controlled thicknesses that correspond to polymer brushes (~90 nm) or to highly crosslinked structures (~1-10 &#956;m). Brush patterns are generated using either the parylene lift-off or interface directed assembly methods described and are useful for precise modulation of overall chemical surface reactivity by adjusting either the PGMA-b-PVDMA pattern density or the length of the VDMA block. In contrast, the thick, crosslinked PGMA-b-PVDMA patterns are obtained using a customized micro-contact printing technique and offer the benefit of higher loading or capture of secondary material due to higher surface area to volume ratios. Detailed experimental steps, critical film characterizations, and trouble-shooting guides for each fabrication method are discussed.

Surface fabrication methods for patterned deposition of nanometer thick brushes or micron thick, crosslinked films of an azlactone block co-polymer are reported. Critical experimental steps, representative results, and limitations of each method are discussed. These methods are useful for creating functional interfaces with tailored physical features and tunable surface reactivity.

In this paper, fabrication methods that generate novel surfaces using the azlactone-based block co-polymer, poly (glycidyl methacrylate)-block-poly (vinyl ...

Radio Frequency Magnetron Sputtering of GdBa2Cu3O7&#8722;&#948;/ La0.67Sr0.33MnO3 Quasi-bilayer Films on SrTiO3 (STO) Single-crystal Substrates

Here, we demonstrate a method of coating ferromagnetic La0.67Sr0.33MnO3 (LSMO) nanoparticles on (001) SrTiO3 (STO) single-crystal substrates by radio frequency (RF) magnetron sputtering. LSMO nanoparticles were deposited with diameters from 10 to 20 nm and heights between 20 and 50 nm. At the same time, (Gd) Ba2Cu3O7&#8722;&#948; ((Gd) BCO) films were fabricated on both undecorated and LSMO nanoparticle decorated STO substrates using RF magnetron sputtering. This report also describes the properties of GdBa2Cu3O7&#8722;&#948;/ La0.67Sr0.33MnO3 quasi-bilayer films structures (e.g., crystalline phase, morphology, chemical composition); magnetization, magneto-transport, and superconducting transport properties were also evaluated.

Radio Frequency Magnetron Sputtering of GdBa2Cu3O7ÃƒÂ¢Ã‹â€ &#039;ÃƒÅ½ ´/ La0.67Sr0.33MnO3 Quasi-bilayer Films on SrTiO3 STO Single-crystal Substrates

Here, we present a protocol to grow LSMO nanoparticles and (Gd) BCO films on (001) SrTiO3 (STO) single-crystal substrates by radio frequency (RF)-sputtering.

Here, we demonstrate a method of coating ferromagnetic La0.67Sr0.33MnO3 (LSMO) nanoparticles on (001) SrTiO3 (STO) single-crystal substrates by radio ...

Synthesis, Functionalization, and Characterization of Fusogenic Porous Silicon Nanoparticles for Oligonucleotide Delivery

With the advent of gene therapy, the development of an effective in vivo nucleotide-payload delivery system has become of parallel import. Fusogenic porous silicon nanoparticles (F-pSiNPs) have recently demonstrated high in vivo gene silencing efficacy due to its high oligonucleotide loading capacity and unique cellular uptake pathway that avoids endocytosis. The synthesis of F-pSiNPs is a multi-step process that includes: (1) loading and sealing of oligonucleotide payloads in the silicon pores; (2) simultaneous coating and sizing of fusogenic lipids around the porous silicon cores; and (3) conjugation of targeting peptides and washing to remove excess oligonucleotide, silicon debris, and peptide. The particle&#8217;s size uniformity is characterized by dynamic light scattering, and its core-shell structure may be verified by transmission electron microscopy. The fusogenic uptake is validated by loading a lipophilic dye, 1,1&#39;-dioctadecyl-3,3,3&#39;,3&#39;-tetramethylindocarbocyanine perchlorate (DiI), into the fusogenic lipid bilayer and treating it to cells in vitro to observe for plasma membrane staining versus endocytic localizations. The targeting and in vivo gene silencing efficacies were previously quantified in a mouse model of Staphylococcus aureus pneumonia, in which the targeting peptide is expected to help the F-pSiNPs to home to the site of infection. Beyond its application in S. aureus infection, the F-pSiNP system may be used to deliver any oligonucleotide for gene therapy of a wide range of diseases, including viral infections, cancer, and autoimmune diseases.

We demonstrate the synthesis of fusogenic porous silicon nanoparticles for effective in vitro and in vivo oligonucleotide delivery. Porous silicon nanoparticles are loaded with siRNA to form the core, which is coated by fusogenic lipids through extrusion to form the shell. Targeting moiety functionalization and particle characterization are included.

With the advent of gene therapy, the development of an effective in vivo nucleotide-payload delivery system has become of parallel import. Fusogenic ...