Iwao Sugimoto

Oriented hydrocarbons transferred from a high performance lubricative amorphous C:H:Si film during sliding in a vacuum

Amorphous C:H containing silicon film shows an extremely low friction coefficient of 0.007 when the film is rubbed with a steel ball in a vacuum. This film is deposited on steel with an electron cyclotron resonance plasma of ethylene and silane. Polarized microinfrared spectroscopy reveals that high lubrication performance is attributed to hydrocarbons transferred from the rubbed film to the ball surface and oriented along the sliding direction.

Molecular sensing using plasma polymer thin-film probes☆

Abstract A selective and sensitive molecular sensing system can be constructed by using plasma polymer films as the sensor probe and statistical molecular classification techniques. Plasma polymer films are likely to contain stable radical sites and conjugated moieties that can interact with target molecules. When quartz crystal microbalances are coated with these films, a dynamic piezoelectric response results, which can be classified using principal-component analysis. These responses reflect the sorption—desorption equilibrium of target molecules through specific interactions.

Solid lubricating fluorine-containing polymer film synthesized by perfluoropolyether sputtering

Novel lubricating fluorine-containing thin films are obtained by r.f. sputtering using perfluoropolyether (PFPE) and polytetrafluoroethylene-PFPE grease as target materials. From IR and X-ray photoelectron spectroscopy analysis, these films are found to consist of olefin and perfluoroalkyl groups. The films not only have superior self- lubricating properties but are also hard and electrically conductive. Direct relationships exist between the molecular structures and the performance characteristics of the films.

Discrimination of odorants of definite concentrations by using plasma-organic-film-coated QCR sensors

Abstract Odorant-discrimination experiments were conducted for the major single-odor substances in various types of botanical species such as fruits and flowers by using a gas-sensing system consisting of a sensor array of quartz crystal resonators (QCRs) and a pattern-recognition technique. The sensing devices were fabricated by radio-frequency sputtering of biomaterials or polymers on to the QCRs. The 22 tested odorants of definite concentration, 0.1–64 ppm, were well discriminated by principal component analysis, using the sensors steady-state and dynamic properties as parameters. From the 1-nearest-neighbor method, introduced to evaluate the discrimination capability, the best discrimination was obtained, using the frequency changes in QCRs for longer than 10 min and the time constant of adsorption at 5 min as parameters, with the success rate of 83%. This system is thus highly reliable for discriminating trace amounts of odorants.

Odorant detection capability of QCR sensors coated with plasma deposited organic films

Odorant-detection experiments were conducted on major single-odor substances in various types of botanical species. The sensing devices we used were quartz-crystal resonators (QCRs), radio-frequency (RF) sputtered with amino acids or polymers. The odorants were generated at very low concentrations (ppb level) by using the diffusion-tube method. The tested odorants were detected at concentrations between 0.3 and 940 ppb. These deposited films had high partition coefficients for the odorants, confirming their high sensitivity to organic vapors, especially to terpenoids. This indicates that the odorant solvation is due to odorant-film interaction related to Gibbs free energy.

Plasma‐synthesized fluoropolymer films for molecular sensing probes

Fluoropolymer films deposited on quartz crystals by radio‐frequency sputtering of polychlorotrifluoroethylene can be used for molecular sensing probes. For several organic materials, the piezoelectric responses of these sensing probes can be classified into characteristic categories. These responses are especially distinctive for highly fluorinated molecules. A film with highly halogenated frameworks shows slow sorption‐desorption response to alternate exposures to acetone atmosphere and to air.

Petroleum pollution sensing at ppb level using quartz crystal resonators sputtered with porous polyethylene under photo-excitation

Abstract Radio-frequency (r.f.) sputtering of a porous polyethylene (PE) disk made by sintering PE granules can be used to form hydrocarbon-polymer films applied as the chemical-sensing overlayers of quartz crystal resonator sensors that can detect petroleum hydrocarbon vapors at low parts-per-billion (ppb) levels. The vapor-sorption capabilities of these films are profoundly affected by the sputtering method used; they are enhanced by photo-excitation through irradiation using ultraviolet (UV) light, and reduced by carbonization induced by long-term processing or by water-treatment. The PE films, especially photo-excited PE film, are characterized by a smooth surface, a high atomic density with a high hydrogen content, and dangling-bond longevity. Photo-excited PE film are capable of detecting linear hydrocarbon (>C 12 ) vapors below the ppb level. Pre-sorption with water vapor at 9% relative humidity (RH) can enhance the sensing abilities of sensors for petroleum hydrocarbons. The effect of this water treatment on petroleum hydrocarbon sorption is especially prominent for d -phenylalanine-sputtered film.

Application of an array sensor based on plasma-deposited organic film coated quartz crystal resonators to monitoring indoor volatile compounds

The basic response ability of an array sensor based on plasma-deposited organic film-coated quartz crystal resonators (QCRs) was investigated with a view to their use for indoor air monitoring. The array of plasma-deposited organic film-coated QCRs was applied to detect and separate volatile organic compounds (VOCs) including alkanes, aromatic carbons, chlorocarbons, ketones, and alcohols. Continuous monitoring tests were tried in a real room environment (a refreshment area and a smoking area) with an array of plasma-deposited organic film-coated QCRs along with commercial sensors for indoor monitoring, a relative humidity/temperature sensor, a carbon dioxide sensor, and a three-dimensional micro-ultrasonic airflow meter. To provide a comparison commercial VOC detectors based on a photo-ionization detector and a semiconductor for indoor monitoring tests were used. The plasma-deposited organic film-coated QCRs exhibited fast pulse responses to volatile compounds in the room air along the baseline shift correlated with relative humidity changes and more sensitive responses compared with commercial organic gas detectors.

Chemical sensing by analysing dynamics of plasma polymer film-coated sensors

Abstract A chemical sensing system that incorporates unique sensor films and uses pattern recgonition of their dynamic responses is presented. This system consists of a sensor array of quartz-crystal microbalances coated with plasma polymer films. The films, synthesized by radio-frequency sputtering, are useful because of their high density of radical sites and unsaturated bonds. When this sensor array is exposed to a gas, the adsorption and desorption of the target gas causes a dynamic frequency response in each piezoelectric sensor. The sensor response is analysed by an autoregressive model typically to estimate the parameters of dynamic systems. This models coefficients reflect the sensor dynamics, providing pattern vectors that characterize the target gas. Based on this model, classification maps for single gases can be created with these pattern vectors. Thesse maps show that the dynamic sensor response provides useful information for gas classification. This model also confirms that our sensing system can identify the components of a gas mixture.

Lubricating performance enhancement of amorphous silicon carbide film by annealing effects and microbeam analyses of the tribological interface

The lubricating performance of amorphous silicon carbide films deposited by electron cyclotron resonance plasma is greatly improved by annealing at 800 °C. The annealed film has a significantly long lubricating life with a low friction coefficient. Detailed information about the molecular structures at the tribological interface is obtained using microbeam surface analytical methods (micro‐Fourier‐transform‐infrared spectroscopy, laser Raman spectroscopy, micro‐x‐ray‐photoelectron spectroscopy, and scanning Auger microprobe). These analyses show that the lubrication performance is improved as a result of a wear‐resistant molecular network composed of the covalent bonds between poorly hydrogenated silicon and carbon. The low hydrogen content in these moieties is achieved from the high‐temperature annealing effect.