Michał Cichomski

Phosphonate self-assembled monolayers on aluminum surfaces

Substrates of aluminum (Al) deposited by physical vapor deposition onto Si substrates and then chemically reacted with perfluorodecylphosphonic acid (PFDPAlSi), decylphosphonic acid (DPAlSi), and octadecylphosphonic acid (ODPAlSi) were studied by x-ray photoelectron spectroscopy (XPS), contact angle measurements, atomic force microscopy (AFM), and friction force microscopy, a derivative of AFM, to characterize their surface chemical composition, roughness, and micro-/nanotribological properties. XPS analysis confirmed the presence of perfluorinated and nonperfluorinated alkylphosphonate molecules on the PFDPAlSi, DPAlSi, and ODPAlSi. The sessile drop static contact angle of pure water on PFDPAlSi was typically more than 130 degrees and on DPAlSi and ODPAlSi typically more than 125 degrees indicating that all phosphonic acid reacted AlSi samples were very hydrophobic. The surface roughness for PFDPAlSi, DPAlSi, ODPAlSi, and bare AlSi was approximately 35 nm as determined by AFM. The surface energy for PFDPAlSi was determined to be approximately 11 mNm by the Zisman plot method compared to 21 and 20 mNm for DPAlSi and ODPAlSi, respectively. Tribology involves the measure of lateral forces due to friction and adhesion between two surfaces. Friction, adhesion, and wear play important roles in the performance of micro-/nanoelectromechanical systems. PFDPAlSi gave the lowest adhesion and coefficient of friction values while bare AlSi gave the highest. The adhesion and coefficient of friction values for DPAlSi and ODPAlSi were comparable.

Domain structure of sintered SmCo5 magnets studied by magneticforce microscopy

The domain structure of sintered SmCo5 permanent magnets at the surface perpendicular to the alignment axis was investigated by magnetic force microscopy (MFM). The main domains forming a maze pattern of typically 3–5μm in width and surface reverse spikes of typically 1–2μm in size are observed. This coarse domain structure is similar to those present in sufficiently thick uniaxial crystals with strong magnetocrystalline anisotropy, reported in earlier investigations performed by Bitter pattern method or magneto-optic Kerr microscopy. In addition to the coarse domain structure, a complicated system of the fine surface domains of 10–200nm in width is observed. The thickness of the zone below the surface filled with these fine scale domains is estimated to be 100 nm and their presence is related to the reduction of the magnetostatic energy close to the specimen surface. Practically no correlation between the magnetic domain structure and the surface topography, the latter revealed by atomic force microscopy...

Nanotribological characterization of vapor phase deposited fluorosilane self-assembled monolayers deposited on polydimethylsiloxane surfaces for biomedical micro-/nanodevices

Fluorosilane self-assembled monolayers for polydimethylsiloxane (PDMS) nanochannels are desirable to control the hydrophobicity of the surface to reduce or prevent undesired protein adsorption or cell interactions, critical for the performance of many biomedical micro-/nanodevices. Surface modifications using vapor phase deposition have become increasingly important for some biomedical micro-/nanodevices and have advantages over liquid phase deposition since the vapor phase can permeate more efficiently into nanochannels. In this study, vapor phase deposition was used to deposit four fluorosilanes on PDMS, and deposition conditions for an optimal process were identified. The films were characterized by means of a contact angle analyzer for hydrophobicity and an atomic force microscope for adhesion and friction measurements. The influence of relative humidity, temperature, and sliding velocity on the friction and adhesion behavior is studied. Failure mechanisms of self-assembled monolayers are investigated...

Nanotribological Characterization and Lubricant Degradation Studies of Metal-Film Magnetic Tapes Using Novel Lubricants

In order to improve the durability of metal-film magnetic tapes, novel lubricants, A20H, X-1P, and X, a modified phosphazene, were deposited on the tapes. The adhesion, friction, and wear of the unlubricated/lubricated tapes were investigated using an atomic force microscope (AFM). The degradation of the lubricants was studied using a mass spectrometer in high vacuum. The durability of various unlubricated/lubricated tapes was compared in ambient and in humid air. The AFM test results show that the A20H lubricated tape exhibited lower adhesion and friction than X-1P and X lubricated tapes. The lubricants were believed to be mainly degraded by tribochemical reaction and mechanical shear in high vacuum. In high humidity air, the various lubricated tapes exhibit higher friction than in ambient air. By comparing the tribological performances of the various lubricated tapes to metal particle (MP) tape, it was found that the lubricated metal-film tapes exhibit lower adhesion, friction, and wear than the MP tape.