Electrowetting measurements with mercury showing mercury/mica interfacial energy depends on charging

We demonstrate that the interfacial energy between mercury and mica is a function of charge on the mercury surface, decreasing with increasing positive charge. The contact angle of mercury on mica has been measured as a function of potential applied to the mercury, which forms the working electrode of a cell containing either KC1 or NaF electrolyte solution. At high negative applied potentials, a stable aqueous film exists between the mercury and mica surface. As potential is made less negative, the film collapses and mercury partial1 wets the mica at a critical potential, close to the electrocapillary maximum. Upon increasing the potential further (making the Hg surface more and more positive), the contact angle measured within the mercury continually decreases. Electrowetting with mercury is not unexpected since its interfacial tension with the aqueous phase is known to be a function of applied potential. However, the observed decrease goes against the trend expected from the Young equation if only this effect is considered. To explain the data we must allow the mercury/mica interfacial tension also to vary with applied potential. This variation indicates that the mercury surface is positively charged by contact with mica, consistent with known contact electrification between these two materials. The inherent charges at the mercury interfaces with mica and electrolyte solution result in contact angle changes of some tens of degrees with a change in applied potential of half a volt orders of magnitude less than the potentials required to effect comparable changes in other electrowetting systems.

Elves processing Christmas orders in an office SFX

A sound design that animates elves working in an office processing Christmas orders.

Investigating nanoparticle-substrate interaction in LSPR biosensing using the image-charge theory

Localized surface plasmon resonance (LSPR) has been used to develop optical biosensors. Tuning the resonance wavelength to detect target biomolecules with a particular dipolar resonance is essential when designing LSPR biosensors. In this paper, the interaction of nanoparticles (NPs) with glass substrate (SiO2) for LSPR wavelength is investigated using the concept of the image-charge theory. Using the FDTD method, it is shown how the NP and substrate size change the plasmon wavelength. Next, this phenomenon is interpreted using the analytical electrostatic eigenvalue method.

A new route to prepare multiresponsive organogels from a block ionomer via charge-driven assembly

We report a novel route to prepare multiresponsive organogels through charge-driven assembly between a block ionomer and a diblock copolymer. The ionic complex aggregates to form spherical cores, which are connected by the middle block of the block ionomer to form gels. The organogels are responsive to acids, amines and salts.

Tuning the amino acid sequence of minimalist peptides to present biological signals via charge neutralised self assembly

Nanofibrous materials yielded by the self-assembly of peptides are rich in potential; particularly for the formation of scaffolds that mimic the landscape of the host environment of the cell. Here, we report a novel methodology to direct the formation of supramolecular structures presenting desirable amino acid sequences by the self-assembly of minimalist peptides which cannot otherwise yield the desired scaffold structures under biologically relevant conditions. Through the rational modification of the pK?, we were able to optimise ordered charge neutralised assembly towards in vivo conditions.

Polyoxometalate-based hybrid organogels prepared from a triblock copolymer via charge-driven assembly

We report a novel approach for the preparation of polyoxometalate-based hybrid organogels from a triblock copolymer via charge-induced assembly. The triblock copolymer used is poly(4-vinyl pyridine)-block-poly(ethylene glycol)-block-poly(4-vinyl pyridine) (4VPm-EGn-4VP m), and polyoxometalate (POM) is phosphotungstic acid (HPW). The ionic interaction between the pyridine groups of the 4VPm-EG n-4VPm and HPW drives the assembly of the triblock copolymer to form solvophobic cores. The PEG middle blocks connect and stabilize the different cores to form hybrid organogels. The structures of POM remain unchanged in these hybrid organogels, and the properties of POMs can be preserved, which has been confirmed by the existence of photo-reduction properties of POM in the hybrid organogels. © 2014 the Partner Organisations.