Effects of Bi nonstoichiometry on (Bi0.5+xNa)TiO3 (BNT) ceramics were investigated at x=−1–+2 mol % of Bi0.5 covering Bi deficiency and excess. At all compositions, rhombohedrally symmetric BNT perovskite formed without secondary phases. Increasing x caused smaller grains. Higher piezoelectric coefficient (d33) but lower depolarization temperature (Td) occurred at Bi excess than at Bi deficiency and vice versa. Leakage current at room temperature decreased with decreasing x. Electrical conductivity of the stoichiometric BNT (x=0) from 700 to 900 °C increased with decreasing partial oxygen pressure from 1 to 10−5 atm suggesting n-type conductivity at elevated temperatures.

Abstract. We present a highly repeatable, lithography-free and mold-free method for fabricating flexible optical lenses by in situ curing liquid polydimethylsiloxane droplets on a preheated smooth surface with an inkjet printing process. This method enables us to fabricate lenses with a focal length as short as 5.6 mm, which can be controlled by varying the droplet volume and the temperature of the preheated surface. Furthermore, the lens can be attached to a smartphone camera without any accessories and can produce high-resolution (1 μm) images for microscopy applications.

Fluorescence microscopy is an important technique for cellular and microbiological investigations. Translating this technique onto a smartphone can enable particularly powerful applications such as on-site analysis, on-demand monitoring, and point-of-care diagnostics. Current fluorescence smartphone microscope setups require precise illumination and imaging alignment which altogether limit its broad adoption. We report a multi-color fluorescence smartphone microscope with a single contact lens-like add-on lens and slide-launched total-internal-reflection guided illumination for three common tasks in investigative fluorescence microscopy: autofluorescence, fluorescent stains, and immunofluorescence. The open-source, simple and cost-effective design has the potential for do-it-yourself fluorescence smartphone microscopy.

Effects of Na nonstoichiometry in (Bi0.5Na0.5+x)TiO3 ceramics were investigated in the range of x=(−5)−(+1) mol % of Na0.5. A rhombohedral perovskite structure was maintained at all compositions with no secondary phases. Grain size decreased with Na nonstoichiometry. Piezoelectric coefficient (d33) increased from 74 pC/N at x=0 up to 91 pC/N at x=−3.5 then dropped with further Na deficiency. Depolarization temperature (Td), on the other hand, decreased from 190 °C at x=0 down to 112 °C at x=−3.5 then increased. Rhombohedral lattice distortion (90−α) decreasing with Na deficiency was a key factor for the variation in d33 and Td.

Structure property relations in (1−x)(Bi0.5Na0.5)TiO3-xBaTiO3 ceramics were investigated at x=0–10 mol %. A solid solution with either rhombohedral or tetragonal symmetry was confirmed with a morphotropic phase boundary (MPB) at x=5–7 mol %. Grains became small with increasing x possibly due to grain boundary pinning by BaBi′–BaNa•. Lattice distortion was a key factor affecting piezoelectric coefficient (d33) and depolarization temperature (Td). Both rhombohedral 90−α and tetragonal cT/aT lattice distortion became smaller toward the MPB causing poling by field and depoling by temperature to become easier subsequently resulting in higher d33 but lower Td, and vice versa.