The paper investigates the dynamics of a new multiple bipolar multiple Dielectric Barrier Discharges(DBD) actuator using in large-scale flow control. Particle image velocimetry experiments are performed to characteristic the effectiveness of the multiple bipolar DBD plasma actuator. The results show that the mutual interaction between the electrodes,one major disadvantage of traditional DBD characterized by reverse discharge can be entirely avoided,and a constantly accelerating electric wind velocity can be obtained by using the new multiple bipolar DBD plasma actuator.

In this paper we report the use of plasma-enhanced chemical vapor deposition (PECVD) for the simultaneous deposition and copolymerization of an amino acid with other organic and inorganic monomers. We investigate the fundamental effects of plasma-enhanced copolymerization on different material chemistries in stable ultrathin coatings of mixed composition with an amino acid component. This study serves to determine the feasibility of a direct, facile method for integrating biocompatible/active materials into robust polymerized coatings with the ability to plasma copolymerize a biological molecule (L-tyrosine) with different synthetic materials in a dry, one-step process to form ultrathin coatings of mixed composition. This process may lead to a method of interfacing biologic systems with synthetic materials as a way to enhance the biomaterial-tissue interface and preserve biological activity within composite films.

The plasma polymerization of NIPAAM and titanium isopropoxide monomers into responsive ultrathin films with responsive optical properties using plasma enhanced chemical vapor deposition is reported. The composite ultrathin films possess a large window for potential changes in their refractive index from 1.60 to 1.95. We demonstrated that these polymer films exhibit fast (transition time below 2 s), large, reversible, and repeatable changes to their thickness and refractive index as a function of periodic environmental humidity changes. (c) 2012 Elsevier Ltd. All rights reserved.

The thermal bimorph is a very popular thermal sensing mechanism used in various applications from meat thermometers to uncooled infrared cameras. While thermal bimorphs have remained promising for scanning thermal microscopy, unfortunately the bending of the bimorph directly interferes with the bending associated with topographical information. We circumvent this issue by creating bimorphs that twist instead of bending and demonstrate the superior properties of this approach as compared to conventional scanning thermal microscopy.

Tailoring the structure of films deposited by plasma-enhanced chemical vapor deposition (PECVD) to specific applications requires a depth-resolved understanding of how the interface structures in such films are impacted by variations in deposition parameters such as feed position and plasma power. Analysis of complementary X-ray and neutron reflectivity (XR, NR) data provide a rich picture of changes in structure with feed position and plasma power, with those changes resolved on the nanoscale. For plasma-polymerized octafluorocyclobutane (PP-OFCB) films, a region of distinct chemical composition and lower cross-link density is found at the substrate interface for the range of processing conditions studied and a surface layer of lower cross-link density also appears when plasma power exceeds 40 W. Varying the distance of the feed from the plasma impacts the degree of cross-linking in the film center, thickness of the surface layer, and thickness of the transition region at the substrate. Deposition at the highest power, 65 W, both enhances cross-linking and creates loose fragments with fluorine content higher than the average. The thickness of the low cross-link density region at the air interface plays an important role in determining the width of the interface built with a layer subsequently deposited atop the first.

TiOxCyNz thin films, plasma-polymerized at room temperature, experienced a significant decrease in film thickness and increase in refractive index with time during air exposure. Correlation of optical and structural changes provided insight into densification mechanisms.

Neutron reflectometry (NR) measurements of ultrathin films from octafluorocyclobutane (OFCB) and benzene (B) precursors deposited using Plasma Enhanced Chemical Vapor Deposition (PECVD) at two pressures (0 6 and 0.05 torr) reveal that under both deposition conditions there are a 7 nm-thick surface layer and an approximately 1 nm-thick transition layer next to the substrate which have structures different than those in the middle of the film NR measurements of films swollen with solvent reveal that the density of cross-linking next to the substrate is lower than that in the middle of the film or the region adjacent to the surface of the film for both precursors Variations in the cross-link density with processing pressure are much stronger for PP-B films than for PP-OFCB films (C) 2010 Elsevier Ltd All rights reserved

A sensitive interferometric method is employed to quantify the deformation of silicon substrates coated with thin plasma-polymerized acrylonitrile film deposited at room temperature. This provides insight into the structural variation of plasma polymerized films.

Analysis of plasma polymerized TiOxCyNz films annealed in the temperature range of 300-700°C, revealed different mechanisms responsible for film densification below 300°C and the formation of TiO2 crystalline phases at temperatures over 500°C.

The interface structure in copolymer films made using plasma enhanced chemical vapor deposition (PECVD) has been probed for the first time using X-ray reflectivity. Copolymer films made from comonomers benzene (B), octafluorocyclobutane (OFCB), and hexamethyldisiloxane (HMDS) show extremely sharp interfaces and scattering length density depth profiles that are uniform with depth, making them useful for optical applications. The polymer/air interface has an rms roughness (similar to 5 angstrom) that is only slightly larger than that of the supporting substrate (similar to 3 angstrom). Addition of either benzene or HMDS as a comonomer in the deposition of OFCB alters a transient deposition behavior at the silicon oxide interface that occurs when using only OFCB. For the B-OFCB copolymer films, a facile control of refractive index with monomer feed composition is achieved. A nonlinear variation in the X-ray scattering length density with composition for the HMDS-OFCB copolymer films is consistent with the nonlinear visible light refractive index (632.8 nm) variation reported earlier. (C) 2010 Elsevier Ltd. All rights reserved.

Plasma enhanced chemical vapor deposition (PECVD) of biologically active films is investigated for the fabrication of bio-inspired chemical vapor sensors, due to the ability to fabricate thin films with unique surface chemistries.

Metallization and a resulting enhancement in the mechanical properties of periodic porous polymer microstructures via bio-functionalization is reported. The size and density of the gold nanoparticles are tuned by varying the polyamino-acid-deposition technique (solution-assisted or vapor-phase deposition) and the conditions of the deposition.

For plasma polymerized (PP) thin films, many practical optical, electronic, sensing, and bio-applications are closely related to their surface properties. In particular, the surfaces of many PP films have a strong affinity for oxygen and moisture. Therefore, three different types of monomers which do not contain oxygen were selected to fabricate PP films, in order to understand the mechanisms for surface oxygen absorption. These monomers were a hydrocarbon, benzene (B); ferrocene (FC), containing Fe ions which have a great affinity for oxygen; and octafluorocyclobutane (OFCB), containing the strong electronegative (and thus oxygen repellent) element fluorine. X-Ray photoelectron spectroscopy (XPS), Fourier transform infra-red (FTIR) spectroscopy, and electron spin resonance (ESR) were used to explore the chemical composition and structure of the resulting PP films. XPS depth-profiling was also used to investigate the oxygen content in the bulk of the films by analyzing the film surface after various amounts of argon etching. The initial oxygen content on the surface of the PP-FC films was the largest of the three while PP-OFCB films only contained a trace quantity. PP-B films had an intermediate concentration. Affinity for oxygen for this latter film was determined to be due to residual activated species including free radicals and dangling bond sites on the film surface. Depth profiling disclosed little oxygen a short distance into the PP-B films, indicating that the oxygen was attracted after deposition upon exposure to ambient conditions. Although the PP-B film exhibited a high concentration of free radicals as determined by ESR, the dense and crosslinked bulk structure shielded these active centers in the film by prohibiting oxygen diffusion. For the PP-FC films, although a decrease in the amount of oxygen was observed after etching, a substantial concentration of oxygen exists with the depth, indicating incorporation of oxygen during the initial deposition. Because of the chemical nature of fluorine, the as-deposited PP-OFCB films did not exhibit significant affinity towards oxygen. However, a slightly oxygen enriched film surface was present after argon etching due to changes in the surface chemistry and structure. These results demonstrate that the formation and distribution of oxygen on and within the PP films are strongly dependent upon the chemical composition and structure of the films.

This communication describes the formation of high index of refraction polymer thin films using a novel plasma polymerization deposition process. A flowing afterglow plasma reactor was modified to enable sublimation of solid samples into the gas phase for subsequent plasma polymerization. Thin films of plasma polymerized ferrocene were deposited on substrates and subsequently characterized. The refractive index as a function of processing conditions was obtained. Relatively high values of n (∼1.73 at 589nm) were obtained. The chemical nature of the polymer thin films was characterized using FTIR and XPS spectroscopy. This work demonstrates that plasma polymerization is an enabling technology for the fabrication of photonic thin films that utilize solid state precursors.

Microcantilevers, one of the most common MEMS structures, have been introduced as a novel sensing paradigm nearly a decade ago. Ever since, the technology has emerged to find important applications in chemical, biological and physical sensing areas. Today the technology stands at the verge of providing the next generation of sophisticated sensors (such as artificial nose, artificial tongue) with extremely high sensitivity and miniature size. The article provides an overview of the modes of detection, theory behind the transduction mechanisms, materials employed as active layers, and some of the important applications. Emphasizing the material design aspects, the review underscores the most important findings, current trends, key challenges and future directions of the microcantilever based sensor technology.

The refractive index is a key characteristic of polymer materials in optical applications. For organic polymers, typical refractive indices are in the range of 1.35 to 1.65. Extending the refractive index beyond the limits is of fundamental scientific interest and would enhance the utility of polymers in many applications. Polymeric thin films fabricated by plasma enhanced chemical vapor deposition (PECVD) have been investigated in the fields of electronics and optics and their utility is becoming more widespread in a variety of applications. Outstanding attributes of the PECVD photonic films include a smooth surface, dense crosslinking structure, robustness, environmental resistance, optical transparency in either visible or IR regions, and good adhesion to many optical window and substrate materials. In recent years, our laboratory has fabricated novel polymer optical coatings and films by PECVD. One focus of this research has been to expand the achievable maximum refractive index. This goal has been sought using two approaches including increasing the conjugation and crosslinking of chemical moieties of the bulk film and incorporation of metal ions into the structure. The techniques of XPS, FTIR, HRSEM, and ellipsometry were used to characterize both the optical properties and the chemical structure of plasma polymerized benzene, ferrocene, and metal-phthalocyanine thin films. The structure-property relationship and the effect of PECVD processing conditions are also discussed in this presentation.

Plasma copolymerization is utilized to fabricate thin photonic films based on hexamethyldisiloxane (HMDSO, C6H18Si2O) and octafluorocyclobutane (OFCB, C4F8). The structure of the plasma copolymerized films is examined by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR), and the optical properties including, refractive index, it, and extinction coefficient, k, are determined by spectroscopic ellipsometry. The refractive indices, which range from 1.38 to 1.54, can be manipulated by adjusting the volume ratio of the two monomers, HMDSO and OFCB, during the polymerization. A nonlinear relationship between the refractive index and extinction coefficient with comonomer feed ratio is observed. A strong initial increase in both it and k as the amount of HMDSO is increased is attributed to significant defluorination of the resultant polymer films coupled with the formation of a C-C rich crosslinked network. Once the network incorporates substantial amounts of Si-C and Si-O bonds, the refractive index starts to decrease slowly due to a lowering of the density. XPS and FTIR results confirm the changes in internal structure consistent with this mechanism.

Stimuli-responsive microactuators controlled by the interfacial stress across the polymer/silicon interface are introduced as simple, miniature, and flexible sensing platforms for chemical vapor detection. The sensors detect water vapor with sensitivities of 10 parts per billion (+/-0.00005% relative humidity) and faster than previously recorded response times. These characteristics make the bimaterial silicon cantilevers excellent candidates for critical security and defense needs as well as for environmental monitoring.

Polymer dielectric films fabricated by plasma enhanced chemical vapor deposition (PECVD) have inherent superiority due to their smooth surface, pin-hole free morphology, and dense crosslinked bulk structure. These spatially uniform films also exhibit good adhesion to a variety of substrates, excellent chemical inertness, high thermal resistance, and are formed from a rapid, inexpensive, solvent-free, room temperature process. In this work, we describe PECVD polymer dielectric films prepared from three precursors including benzene, octafluorocyclobutane (OFCB) and hexamethyldisiloxane (HMDS) using two different feed locations including in the plasma zone center and in the downstream region. The chemical structure of the PECVD films was determined by XPS, FTIR and ESR. The dielectric constant and dissipation of the films were studied over a range of frequencies up to 1 MHz, and the dielectric strength was characterized by the current-voltage method. Spectroscopic ellipsometry was performed to determine the thickness and refractive index of the resultant films.The PP-benzene films showed strong aromatic characteristics, PP-OFCB films maintained a high F/C ratio with a variety of fluorine moieties, and PP-HMDS retained a large fraction of Si-O bonds. All the PECVD films showed higher dielectric constants than those of corresponding conventional polymers. There is a small sharp drop in dielectric constant at low frequencies for all the PECVD films, attributed to the orientational polarization caused by trapped free radicals, oxygenated groups (C=O), and unsaturated moieties. The largest drop occurred for the PP-HMDS films. All films exhibit a continuous increase in dielectric loss as a function of frequency. Among all the PECVD films, the PP-benzene exhibited high breakdown strength. These variations in the dielectric properties are closely associated with the unique structure features of PECVD films.