Micrometer scale

Several micromanometers, based on the liquid-column principle and possessing extreme precision and sensitivity, have been developed for measuring minute gas-pressure differences and for cahbrating low-range gauges. Some of these micromanometers are available commercially. These micromanometers are free from errors due to capillarity and, aside from checking the micrometer scale, require no cahbration. See Doolittle, op. cit., p. 21. 

The resolution of infra-red densitometry (IR-D) is on the other hand more in the region of some micrometers even with the use of IR-microscopes. The interface is also viewed from the side (Fig. 4d) and the density profile is obtained mostly between deuterated and protonated polymers. The strength of specific IR-bands is monitored during a scan across the interface to yield a concentration profile of species. While in the initial experiments on polyethylene diffusion the resolution was of the order of 60 pm [69] it has been improved e.g. in polystyrene diffusion experiments [70] to 10 pm by the application of a Fourier transform-IR-microscope. This technique is nicely suited to measure profiles on a micrometer scale as well as interdiffusion coefficients of polymers but it is far from reaching molecular resolution. 

Besides crystalline order and structure, the chain conformation and segment orientation of polymer molecules in the vicinity of the surface are also expected to be modified due to the specific interaction and boundary condition at the surface between polymers and air (Fig. 1 a). According to detailed computer simulations [127, 128], the chain conformation at the free polymer surface is disturbed over a distance corresponding approximately to the radius of gyration of one chain. The chain segments in the outermost layers are expected to be oriented parallel to the surface and chain ends will be enriched at the surface. Experiments on the chain conformation in this region are not available, but might be feasible with evanescent wave techniques described previously. Surface structure on a micrometer scale is observed with IR-ATR techniques [129],... 

The solid-liquid two-phase flow is widely applied in modern industry, such as chemical-mechanical polish (CMP), chemical engineering, medical engineering, bioengineering, and so on [80,81]. Many research works have been made focusing on the heat transfer or transportation of particles in the micro scale [82-88], In many applications, e.g., in CMP process of computer chips and computer hard disk, the size of solid particles in the two-phase flow becomes down to tens of nanometres from the micrometer scale, and a study on two-phase flow containing nano-particles is a new area apart from the classic hydrodynamics and traditional two-phase flow research. In such an area, the forces between particles and liquid are in micro or even to nano-Newton scale, which is far away from that in the traditional solid-liquid two-phase flow. 

In many cases of traditional tribology, friction and wear are regarded as the results of surface failure of bulk materials, the solid surface has severe wear loss under high load. Therefore, the mechanical properties of bulk material are important in traditional friction and wear. However, in microscale friction and wear, the applied load on the interactional surface is light and the contact area is also under millimeter or even micrometer scale, such as the slider of the magnetic head whose mass is less than 10 mg and the size is in micrometer scale. Under this situation, the physical and chemical properties of the interactional surface are more important than the mechanical properties of bulk material. Figure 1 shows the general differences between macro and micro scale friction and wear. 

The principles of application of zeolite membranes at the microlevel can be very similar to those on the particle level, but now at the crystal (micrometer) scale, enclosing the active catalytic material. 

As has been shown above, oscillatory electrodeposition is interesting from the point of view of the production of micro- and nanostructured materials. However, in situ observation of the dynamic change of the deposits had been limited to the micrometer scale by use of an optical microscope. Inspections on the nanometer scale were achieved only by ex situ experiments. Thus, information vdth regard to dynamic nanostructural changes of deposits in the course of the oscillatory growth was insufHcient, although it is very important to understand how the macroscopic ordered structures are formed with their molecular- or nano-components in a self-organized manner. 

As already indicated above, what one may consider a surface depends on the property under consideration. Adhesion is very much an outer atomic layer issue, unless one is dealing with materials like fibreboard in which the polymer resin may also be involved in mechanical anchoring onto the wood particles. Gloss and other optical properties are related to the penetration depth of optical radiation. The latter depends on the optical properties of the material, but in general involves more than a few micrometer thickness and therewith much more than the outer atomic layers only. It is thus the penetration depth of the probing technique that needs to be suitably selected with respect to the surface problem under investigation. Examples selected for various depths (< 10 nm, 10 s of nm, 100 nm, micrometer scale) have been presented in Chapter 10 of the book by Garton on Infrared Spectroscopy of Polymer Blends, Composites and Surfaces... 

The electrostatic field in solution is important on the wafer scale but may negligible on the micrometer scale corresponding to the interconnect lines. The significance of the field within a trench can be quantified by their parameter cs-,... 

The nanometer- to micrometer-scale dimensions of supramolecular assemblies present many challenges to rigorous compositional and structural characterization. Development of adequate structure-property relationships for these complex hierarchical systems will require improved measurement methods and techniques. The following areas constitute critical thrusts in instrument development. 

Figure 10. Schematic showing the conversion of a porous membrane into a template in which the pores are filled or coated to form random ensembles or ordered arrays of nanometer- and micrometer-scale cylinders or tubes. (Derived with permission from ref 87. Copyright i997 Electrochemical Society.)...

Finally, hyperbranched polymer layers by surface-initiated step polymerization was intensively studied mainly by Bergbreiter et al. and Crooks et al. Patterned surfaces were prepared on the micrometer scale and a variety of functional groups introduced interesting optical, electrochemical, biological, and mechanical properties into the films. For a recent review on surface-initiated step polymerization resulting in branched polymer layers see [352]. 

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