Hierarchically structured surfaces

Rodriguez-Hemandez, J. Nano/micro and hierarchical structured surfaces in polymer blends. In Thomas, S., Shanks, R., Chandrasekharakurup, S. (eds.) Nanostructured Polymer Blends, pp. 357 21. William Andrew, Oxford (2014)... 

Incorporation of structural hierarchy enhances the superhydrophobicity further. Jxmg et at have compared the nanostructured and hierarchical surfaces of CNTs [221]. The hierarchal structure is formed by applying CNT on microstructures Si replica. With a contact angle of 170°, the hierarchical structured surfaces exhibit higher superhydrophobic nature as compared to that of nanostructured surface (contact angle 166°). 

Reproduced with permission from J. Rodriguez-Hernandez, Chapter 11. Nano/Micro and hierarchical structured surfaces in polymer blends, in S. Thomas, R. Shanks,... 

They observed cylindrical microdomains upon microphase separation of the BCR However, addition of the homopolymer modified both the diameter and spacing of the moieties whereas the spatial order and orientation remains. Selective removal of the PMMA either from the BCR or both from BCR and homopolymer leads to pores with two distinct pore sizes. Other BCP/homopolymer blends have also been reported to produce hierarchically structured surfaces with two-fold nanometer and micrometer length scales in porous polymer films [42],... 

Control over the stmcturation process permits not only the modification of the dimensions of a particular morphology but also order-order transitions between two different microphases. Equally, these transitions can be accompanied by macrophase separation, thus leading to hierarchically structured surfaces. Finally, this chapter analyzes the role of BCP blends in a few selected examples. Surface patterning, the elaboration of ACs or nanostructured hydrogels, or the fabrication of sophisticated stimuli-responsive surfaces are a few of the applications that currently take advantage of these polymeric systems. 

Hierarchical structured surfaces have also been obtained by combining photolithography and dry etching methods, as typically used in MEMS fabrication [56, 57]. Single crystal silicon posts (1 [xm in diameter and height up to 50 [xm) supporting... 

This chapter summarizes the main aspects concerning the preparation of homopolymer and BC blends in thin films. Thin films of polymer blends have been found useful in many different applications not only in the preparation of novel devices, but also for the preparation of hierarchically structured surfaces, superhydrophobic surfaces or in electronics and optoelectronics, just to mention a few. 

Verho,T., Korhonen.J.T., Sainiemi, L.,Jokinen,V., Bower, C., Franze, K., Franssila, S., Andrew, P, Ikkala, O., Rasa, R.H.A., 2012. Reversible switching between superhydrophobic states on a hierarchically structured surface. Proc. Natl. Acad. Sci. USA 109,10210. 

Hierarchical Structures Huberman and Kerzberg [huber85c] show that 1// noise can result from certain hierarchical structures, the basic idea being that diffusion between different levels of the hierarchy yields a hierarchy of time scales. Since the hierarchical dynamics approach appears to be (on the surface, least) very different from the sandpile CA model, it is an intriguing challenge to see if the two approaches are related on a more fundamental level. 

The thermal properties of C3 materials at high temperatures are most remarkable if protected from oxidation. This issue is discussed below in more detail. If they are not oxidized, the C3 materials exhibit similar stability data as ceramics [22], in particular at temperatures above 1500 K where protective coatings applied behave like a plastic and close developing surface cracks against air attack. C3 materials expose the advantages of their hierarchical structure being present in both filler and binder phase and develop wood-like properties under ambient conditions. A descriptive pa-... 

Following an introductory section on the historical background that has led to the development of RPC techniques as practiced today, the principles and theory of RPC will be discussed, incorporating the role of amino acid sequence and hierarchical structural effects that determine the outcome of the interaction of a peptide(s) with various types of nonpolar chromatographic surfaces. Subsequently, the influence of operating parameters such as the effects of different (1) surface morphologies or chemistries of nonpolar sorbents (2) concentrations of organic solvents, salts, or other mobile-phase additives (3) pH conditions or... 

A possibility for the formation of more complex patterns is the use of prepatterned substrates as presented by several authors by either masking the surface partially to avoid the formation of a hard layer in the masked regions [19] or topographical prepatterning, where a relief structure is modified in order to wrinkle [15-17, 34], Periodic porous structures have been reported to undergo pattern transformation due to buckling instabilities when external forces are applied. This results in more complex hierarchical structures [35-37],... 

Another possible application using the hierarchical nature of the wrinkles has been discussed by Efimenko and coworkers [46], They treated a mechanically stretched PDMS sheet with UV-ozone in order to create a stiff surface layer. A detailed analysis with AFM and profilometry of the wrinkles after releasing the strain showed that the wrinkling patterns are hierarchical themselves. They observed up to five generations of different wavelengths with different periodicities. These features made so structured surfaces valuable candidates for separate colloidal particles of different sizes by acting as a micro fluidic sieve. A suspension... 

Arnold M, Schwieder M, Blummel J et al (2009) Cell interactions with hierarchically structured nano-pattemed adhesive surfaces. Soft Matter 5(l) 72-77... 

Figure 8.28 shows the pore size distributions for the PS formed on highly doped / -Si at different current densities." For the PS formed on heavily doped silicon, the pores at a given HF concentration have a narrower distribution at lower current at a given current density, the distribution is narrower at lower HF concentrations. A bimodal distribution of pore diameter is gena-ally associated with two-layer PS on lowly doped / -Si and iUmninated n-Si. The PS formed on p-Si has also been found to have a bimodal distribution of particles sizes small spherically shaped particles with a diameter of a few nanometers and large cylindrically shaped particles oriented with their axis perpendicular to the surface.The distribution of pore size with multiple peaks may be attributed to the fact that PS may have a surface micropore layer and smaller branched pores. Due to the hierarchical structure of the branched pores, the distribution of pore diameters for highly branched PS is found to be fractal-like. ° ... 

Techniques to produce multiscale biomaterial scaffolds with designer geometries are the need of the hour to provide improved biomimetic properties for functional tissue replacements. While micrometer fibers generate an open pore stnicture, nanofibers support cell adhesion and facilitate cell-cell interactions. This was further proven by cell penetration studies, which showed superior ingrowth of cells into hierarchical structures. Mixed bimodal scaffolds of two different polymers are another promising approach, because they exhibit hierarchical pore/ surface systems and combine the beneficial properties of both polymers at two different scales. Vaiious 3D micro- and nanoscale multiscale scaffolds have been fabricated through various techniques and were found to have the potential to essentially recreate natural bone, cardiac, neural, and vascular tissues. 

---