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Materials in the classes of skutterudites and clathrates are considered good thermoelectrics due to their low thermal conductivity. This is normally attributed to the effect of 'rattling' atoms that induce a disordered structure known as a 'phonon glass'. Experimental studies now elucidate the effect of rattlers and demonstrate that they induce glass-like conductivity, even if the phonon-glass picture may not be appropriate.
Philips has recently changed its focus from electronic components to healthcare innovations. Nature Materials talked to Hans Hofstraat about the reasons behind this choice and how it affected Philips Research scientists.
The low thermal conductivity of some thermoelectric materials is commonly attributed to rattlers — atoms trapped in oversized cages. Two independent studies now show that rattlers indeed reduce thermal conductivity to glass-like values.
Careful design of donor–acceptor polymer molecules with reversible redox properties gives access to polymer electrochromic displays with switchable absorption in the full visible range of the optical spectrum.
Using a known and widely used drug as a specific triggering agent, another drug can be released from a hydrogel. This route opens up the application of hydrogels in the targeted, controlled release of drugs in vivo.
Artificial photosynthesis — splitting water with light — is an attractive way to make hydrogen, but what happens to the oxygen? A catalyst that aids in the efficient production of gaseous oxygen improves the viability of this approach.
Ammonia is an important compound for producing pharmaceuticals, fertilisers and explosives. It is known to form hydrogen-bonded solids at high pressure, but ionic solids of ammonium amide are now predicted at even higher pressure.
A new, asymmetric glassy state is identified in soft colloidal mixtures composed of large and small star polymers. The results will enable the design, control and tuning of the rheological properties of other soft composite materials.
Developing novel strategies to drive or manipulate the migration of particles in solutions is important for lab-on-a-chip technologies, especially in the context of biological and chemical analysis. A strongly amplified and tunable migration of large particles using a passive transport phenomenon is now reported.
The structure of C60 is well-known: a perfectly symmetrical sphere of 12 isolated pentagons. But this is only one of 1,812 possible isomers, and the only one to obey the isolated-pentagon rule. So far it has been the only form observed. But now two isomers without isolated pentagons have been made.
Smart windows and switchable displays require electrochomic materials that change their optical properties on electron transfer. Organic polymers offer further benefits including high contrast, greater colour variety and flexible substrates, but their use has remained challenging. Now, a donor–acceptor approach has yielded the first neutral black polymeric electrochrome.
Stimuli-responsive hydrogels show potential as smart materials for drug delivery, however, the triggers used must be applicable in vivo. Now, a hydrogel has been synthesized that contains protein–protein interactions that respond to a specific pharmaceutical drug and enable the hydrogel to controllably release its load of a human growth factor, which increases cell proliferation.
The low thermal conductivity in filled skutterudites has been ascribed to rattling atoms inducing a phonon glass. Experimental evidence now shows that the phonon glass description is incorrect, and provides essential insight for the development of microscopic models aimed at describing the thermoelectric properties of these materials.
The presence of guest atoms—known as rattlers—in the cages of some clathrate structures is considered to be responsible for the low thermal conductivity of the materials. Neutron spectroscopy provides important evidence regarding the actual phonon dispersion in the material, and the precise way in which this is influenced by rattlers.
Cell–matrix interactions have critical roles in regeneration, development and disease. Encapsulated human mesenchymal stem cells can now be induced to differentiate down osteogenic and adipogenic pathways by controlling their three-dimensional environment using tethered small-molecule functional groups.
We explore the motivations for some physical scientists to move away from their original research field and use their background to contribute to the development of biomedical applications, as well as the reasons why some companies traditionally operating in the consumer electronics sector expand into healthcare.