Search for: All records

Aluminum nitride is a white, hydrophilic, high-band-gap ceramic. Here we report on the light-induced evaporation of saltwater through a capillary wick composed of drop-cast microparticles. Saltwater evaporation rates are significantly higher than expected. Our results point to significant potential for this interface-driven approach in solar non-thermal desalination and water separation technologies. 

The aluminum nitride bandgap energy matches the binding energy between salt and water molecules. Here we study the effect of 405-nm light on the rates of evaporation when saline solutions are im-bibed within a porous ceramic aluminum nitride wick. Sensitive measurements are taken in a self-referencing setup and compared with the capillary fluid response. Evaporation rates increase with light illumination when the solution is more saline in a manner that indicates interfacial charge-transfer characteristics. Our results show consistent trends and strong potential for photonic environmental applications in salt-water separation 

Aluminum nitride (AlN) is a high-bandgap, high-optical-refractive-index, electrical insulator with epsilon-near-zero behavior in the infrared atmospheric window. To-wards binderless additive manufacturing of porous AlN, we demonstrate a 370% increase in hardness through laser sintering. 

With time-resolved measurements, we investigate the inverse Faraday effect of gold nanodisks in random monolayers. Order-of-magnitude enhancements are observed for 3.9% fill-factor samples (compared to gold film) which increases with proximity to the plasmonic resonance. 

We demonstrate a compact, portable and reliable, poor-man’s 8-channel interconnect and measure, in the 50- 100 MHz VHF radiofrequency range, the path-dependent voltage transfer function across drop-cast poly(3,4- ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). The setup may be inexpensively deployed for single-input-multiple-output (SIMO) self-sensing materials with computational impedance tomography algorithms. We test our setup with PEDOT:PSS samples that are dried in a static magnetic field. These samples exhibit anisotropic electrical conductivities and nanostructure morphologies. Voltages across the sample vary 2dB as a result of this anisotropy. This processing-dependent anisotropy of PEDOT:PSS may be useful in future efforts aimed at deconvolving the path-dependent electrical tomography measurements, as necessary for such a sensing system. 

The role of convection in liquid thermoelectric cells may be difficult to predict because the inter- and intramolecular interactions are not currently incorporated into thermodynamic models. Here, we study the thermoelectric response of a series of five anhydrous 1-methyl-3- alkylimidazolium halide ionic liquids with varied chain length and counterion in a high-aspect-ratio, horizontal-temperature-gradient geometry, where convection is minimal. While a canonical constant-volume thermodynamic model predicts that the longer aliphatic groups exhibit larger Seebeck coefficients, we instead measure the opposite: Longer aliphatic chains correlate with lower densities and greater heat expansion, stronger intermolecular associations, stronger steric repulsion, and lower Seebeck coefficients. As evidence of the critical role of thermal expansion, we measure that the Seebeck effect is nonlinear: Values of −2.8 mV/K with a 10 K temperature difference and −1.8 mV/K with a 50 K difference are measured with ether ion. Our results indicate that steric repulsion and heat expansion are important considerations in ionic liquid design; with large temperature differences, the Seebeck coefficient correlates negatively with heat expansion. Our results suggest that Seebeck values will improve if thermal expansion is limited in a pressurized, isochoric, convection-free design. 

When we illuminate gold nanofluids over indium-tin-oxide (ITO)-coated substrates, nanoparticle chains selfassemble via optical binding forces. We speculate that charge transfer between gold and ITO pins nanoparticles to the substrate and reduces the lateral Brownian motion as they attach to the substrate. We correspondingly model the self assembly with additional stochastic or random forces. Simulations show a nonequilibrium phase transition: when the stochastic force is small, nanoparticle chains align perpendicular to the light polarization and nanoparticles settle at shallow but stable nodes; when the stochastic force is large, however, the nanoparticle chains align parallel to the light polarization and nanoparticles settle at saddlepoints where the optical binding force is largely zero. Since the presence and strength of Brownian forces influence which state is formed, we reconsider the role that surfaces have—not only in relation to charge transfer but also heat transfer.