A promising path for introducing rapid modulation into fibres would be through the piezoelectric effect [10][11] . Embedding piezoelectric domains would allow fibres to be electrically actuated over broad frequencies on the one hand, and to function as sensitive broadband microphones on the other. However, fibres for the most part have been made of materials in the disordered glassy state precluding the crystalline symmetry requirements necessary for piezoelectricity.Recent progress in drawing of fibres made of a multiplicity of materials 12 present new opportunities for re-examining this challenge. With this approach, fibre materials are drawn from 3 preforms in a regime dominated by viscous forces allowing for internal low viscosity domains to be arranged in non-equilibrium cross sections confined by viscous glassy boundary layers. In fact constructing a piezoelectric fibre could be accomplished in a straightforward manner by assembling a preform made of a piezoelectric material poly(vinylidene fluoride) (PVDF) 13-14 , with metal electrodes and an insulating polymer, which would be followed by a thermal draw.The stress present during the fibre draw should in principle induce the non-polar α to the ferroelectric β phase transition in the PVDF layer 13,[15][16] . The process should yield many metres of fibre with built-in internal electrodes which could be utilized to establish the large electric field necessary for poling the PVDF layer. However, upon detailed examination a number of significant challenges and seemingly conflicting requirements arise. The necessity to utilize crystalline materials both for the piezoelectric layer and the electrical conductors leads to the formation of multiple adjacent low viscosity and high aspect ratio domains. These domains undergoing a reduction in cross sectional dimensions are susceptible to capillary breakup and mixing during fibre drawing due to flow instabilities. Layer thickness non-uniformity either in the lateral or in the longitudinal directions [17][18] precludes the formation of the coercive field needed for poling. Moreover, even if capillary breakup were kinetically averted and uniform sections of fibres were to emerge they would not exhibit piezoelectricity because the stress and strain conditions necessary to induce the thermodynamic phase transition in PVDF cannot be sustained in the fibre draw process.To address these challenges we choose to focus our attention on the ability to maintain geometric coherence and layer thickness uniformity. A viscous and conductive carbon-loaded poly(carbonate) (CPC) is used to confine the low viscosity crystalline piezoelectric layer during 4 the draw process. The CPC layers exhibit high viscosity (10 5~1 0 6 Pa·s) at the draw temperature and adequate conductivity (1~10 4 ohm·m) over the frequency range from DC to tens of MHz, thus facilitating short range (hundreds of microns) charge transport on length scales associated with the fibre cross section. Then a piezoelectric polymer which crystallizes into the appropriate phase...

The selective hybridization of DNA is of key importance for many practical applications such as gene detection and DNA-mediated self-assembly. These applications require a quantitative prediction of the hybridization free energy. Existing methods ignore the effects of non-complementary ssDNA tails beyond the first unpaired base. We use experiments and simulations to show that the binding strength of complementary ssDNA oligomers is altered by these sequences of non-complementary nucleotides. Even a small number of non-binding bases are enough to raise the hybridization free energy by approximately 1 kcal/mol at physiological salt concentrations. We propose a simple analytical expression that accounts quantitatively for this variation as a function of tail length and salt concentration.

Nickel-rich lithium nickel-manganese-cobalt oxide cathodes, in particular Li(Ni 0.8 Mn 0.1 Co 0.1 )O 2 (NMC811), are currently being commercialized as next generation cathode materials, due to their increased capacities compared to current materials. Unfortunately, the higher nickel content has been shown to accelerate cell degradation and a better understanding is needed to maximize cell lifetimes. NMC811/graphite cells were tested under stressed conditions (elevated temperature and cell voltages) to accelerate degradation focusing on transition metal (TM) dissolution from the cathode. Increasing the cell temperature, upper cutoff voltage (UCV) and number of cycles all accelerated capacity fade and diffraction studies showed that under stressed conditions, additional degradation mechanisms beyond lithium loss to the SEI are present. Significant TM dissolution and subsequent deposition on the graphite anode is seen, particularly at stressed conditions. The concentration of TMs in the electrolyte remained invariant with cycling conditions, presumably reflecting the limited solubility of these ions and emphasizing the role that TM deposition on the anode plays in continuing to drive dissolution. Significant deposits of metals from the cell casings and current collectors were also detected at all cycling conditions, indicating that corrosion and metal leaching can be as important as TM dissolution from the active material in some cell formats.

Improved analytical tools are urgently required to identify degradation and failure mechanisms in Li-ion batteries. However, understanding and ultimately avoiding these detrimental mechanisms requires continuous tracking of complex electrochemical processes in different battery components. Here, we report an operando spectroscopy method that enables monitoring the chemistry of a carbonate-based liquid electrolyte during electrochemical cycling in Li-ion batteries with a graphite anode and a LiNi0.8Mn0.1Co0.1O2 cathode. By embedding a hollow-core optical fibre probe inside a lab-scale pouch cell, we demonstrate the effective evolution of the liquid electrolyte species by background-free Raman spectroscopy. The analysis of the spectroscopy measurements reveals changes in the ratio of carbonate solvents and electrolyte additives as a function of the cell voltage and show the potential to track the lithium-ion solvation dynamics. The proposed operando methodology contributes to understanding better the current Li-ion battery limitations and paves the way for studies of the degradation mechanisms in different electrochemical energy storage systems.