Browsing by Subject "Polymer Science"
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Item Open Access Influence of humidity on tribo-electric charging and segregation in shaken granular media.(Soft matter, 2017-01) Schella, André; Herminghaus, Stephan; Schröter, MatthiasWe study the effect of humidity on the charge accumulation of polymer granulates shaken vertically in a stainless steel container. This setup allows us to control the humidity level from 5% to 100%RH while performing automated charge measurements in a Faraday cup directly connected to the shaking container. We find that samples of approximately 2000 polymer spheres become highly charged at low humidity levels (<30%RH), but acquire almost no charge for humidity levels above 80%RH. The transition between these two regimes does depend on the material, as does the sign of the charge. For the latter we find a correlation with the contact angle of the polymer with only very hydrophilic particles attaining positive charges. We show that this humidity dependence of tribo-charging can be used to control segregation in shaken binary mixtures.Item Open Access Measuring the configurational temperature of a binary disc packing.(Soft matter, 2014-06) Zhao, Song-Chuan; Schröter, MatthiasJammed packings of granular materials differ from systems normally described by statistical mechanics in that they are athermal. In recent years a statistical mechanics of static granular media has emerged where the thermodynamic temperature is replaced by a configurational temperature X which describes how the number of mechanically stable configurations depends on the volume. Four different methods have been suggested to measure X. Three of them are computed from properties of the Voronoi volume distribution, the fourth takes into account the contact number and the global volume fraction. This paper answers two questions using experimental binary disc packings: first we test if the four methods to measure compactivity provide identical results when applied to the same dataset. We find that only two of the methods agree quantitatively. This implies that at least two of the four methods are wrong. Secondly, we test if X is indeed an intensive variable; this becomes true only for samples larger than roughly 200 particles. This result is shown to be due to recently measured correlations between the particle volumes [Zhao et al., Europhys. Lett., 2012, 97, 34004].Item Open Access Self-Assembling DNA templates for programmed artificial biomineralization(Soft Matter, 2011-05-16) Samano, Enrique C; Pilo-Pais, Mauricio; Goldberg, Sarah; Vogen, Briana N; Finkelstein, Gleb; LaBean, Thomas HComplex materials with micron-scale dimensions and nanometre-scale feature resolution created via engineered DNA self-assembly represent an important new class of soft matter. These assemblies are increasingly being exploited as templates for the programmed assembly of functional inorganic materials that have not conventionally lent themselves to organization by molecular recognition processes. The current challenge is to apply these bioinspired DNA templates toward the fabrication of composite materials for use in electronics, photonics, and other fields of technology. This highlight focuses on methods we consider most useful for integration of DNA templated structures into functional composite nanomaterials, particularly, organization of preformed nanoparticles and metallization procedures. © The Royal Society of Chemistry 2011.