Jaeyeon Pyo

Three-Dimensional Writing of Conducting Polymer Nanowire Arrays by Meniscus-Guided Polymerization

Accurate and versatile three-dimensional writing of individually controlled conducting polymer nanodevices forming dense arrays is demonstrated by guiding a monomer meniscus in pulling a micropipette during oxidative polymerization. We specifically demonstrate well-defined dense arrays of various freestanding nano-components with controlled radius down to similar to 50 nm: straight wires, nanowires with variable radius, branches, and bridges.

3-D worm tracker for freely moving C. elegans.

The manner in which the nervous system regulates animal behaviors in natural environments is a fundamental issue in biology. To address this question, C. elegans has been widely used as a model animal for the analysis of various animal behaviors. Previous behavioral assays have been limited to two-dimensional (2-D) environments, confining the worm motion to a planar substrate that does not reflect three-dimensional (3-D) natural environments such as rotting fruits or soil. Here, we develop a 3-D worm tracker (3DWT) for freely moving C. elegans in 3-D environments, based on a stereoscopic configuration. The 3DWT provides us with a quantitative trajectory, including the position and movement direction of the worm in 3-D. The 3DWT is also capable of recording and visualizing postures of the moving worm in 3-D, which are more complex than those in 2-D. Our 3DWT affords new opportunities for understanding the nervous system function that regulates animal behaviors in natural 3-D environments.

Light propagation in conjugated polymer nanowires decoupled from a substrate

Light-emitting conjugated polymer nanowires are vertically grown and remotely manipulated into a freestanding straight or curved structure in three-dimension. This approach enabled us to eliminate substrate coupling, a critical issue in nanowire photonics in the past decade. We for the first time accomplished characterization of propagation and bending losses of nanowires completely decoupled from a substrate.

Quantitative Probing of Cu2+ Ions Naturally Present in Single Living Cells

Quantitative probing of Cu(2+) ions naturally present in single living cells is realized by developing a quantum-dot-embedded nanowire-waveguide probe. The intracellular Cu(2+) ion concentration is quantified by direct monitoring of photoluminescence quenching during the insertion of the nanowire in a living neuron. The measured intracellular Cu(2+) ion concentration is 3.34 ± 1.04 × 10(-6) m (mean ± s.e.m.) in single hippocampal neurons.

Four-dimensional visualization of rising microbubbles

Four-dimensional imaging, which indicates imaging in three spatial dimensions as a function of time, provides useful evidence to investigate the interactions of rising bubbles. However, this has been largely unexplored for microbubbles, mostly due to problems associated with strong light scattering and shallow depth of field in optical imaging. Here, tracking x-ray microtomography is used to visualize rising microbubbles in four dimensions. Bubbles are tracked by moving the cell to account for their rise velocity. The sizes, shapes, time-dependent positions, and velocities of individual rising microbubbles are clearly identified, despite substantial overlaps between bubbles in the field of view. Our tracking x-ray microtomography affords opportunities for understanding bubble-bubble (or particle) interactions at microscales – important in various fields such as microfluidics, biomechanics, and floatation.

Nanowires: Quantitative Probing of Cu(2+) Ions Naturally Present in Single Living Cells (Adv. Mater. 21/2016).

Quantitative probing of the Cu(2+) ions naturally present in single living cells is accomplished by a probe made from a quantum-dot-embedded-nanowire waveguide. After inserting the active nanowire-based waveguide probe into single living cells, J. H. Je and co-workers directly observe photoluminescence (PL) quenching of the embedded quantum dots by the Cu(2+) ions diffused into the probe as described on page 4071. This results in quantitative measurement of intracellular Cu(2+) ions.