Spatiotemporal Control of Polymorphic Phase Transition of Glycine Crystals by Three-Dimensional Femtosecond Laser Ablation Processing.

Spatiotemporal control of the polymorphic phase transition of glycine crystals was demonstrated by three-dimensional (3D) processing with a focused femtosecond laser pulse as an external stimulus. We found that the transition from a metastable form (ß-form) to more stable ones (α- or γ-form) could be triggered from the irradiated area of not only the surface but also inside of glycine crystals. This 3D processing with a focused femtosecond laser pulse enabled us to precisely monitor the transition dynamics from a targeted position to the entire part of crystals. The systematic study with the space-selective phase transition method revealed that the phase transition inside of glycine crystals was significantly slower (e.g., ∼50 times) than that at the crystal surface, which indicates the crucial role of water molecules in air on the phase transition dynamics. We foresee that this laser method can be a practical tool for monitoring spatiotemporal dynamics of phase transition.

Low Surface Potential with Glycoconjugates Determines Insect Cell Adhesion at Room Temperature.

Cell-coupled field-effect transistor (FET) biosensors have attracted considerable attention because of their high sensitivity to biomolecules. The use of insect cells (Sf21) as a core sensor element is advantageous due to their stable adhesion to sensors at room temperature. Although visualization of the insect cell-substrate interface leads to logical amplification of signals, the spatiotemporal processes at the interfaces have not yet been elucidated. We quantitatively monitored the adhesion dynamics of Sf21 using interference reflection microscopy (IRM). Specific adhesion signatures with ring-like patches along the cellular periphery were detected. A combination of zeta potential measurements and lectin staining identified specific glycoconjugates with low electrostatic potentials. The ring-like structures were disrupted after cholesterol depletion, suggesting a raft domain along the cell periphery. Our results indicate dynamic and asymmetric cell adhesion is due to low electrostatic repulsion with fluidic sugar rafts. We envision the logical design of cell-sensor interfaces with an electrical model that accounts for actual adhesion interfaces.

Fully-printed high-performance organic thin-film transistors and circuitry on one-micron-thick polymer films.

Thin, ultra-flexible devices that can be manufactured in a process that covers a large area will be essential to realizing low-cost, wearable electronic applications including foldable displays and medical sensors. The printing technology will be instrumental in fabricating these novel electronic devices and circuits; however, attaining fully printed devices on ultra-flexible films in large areas has typically been a challenge. Here we report on fully printed organic thin-film transistor devices and circuits fabricated on 1-µm-thick parylene-C films with high field-effect mobility (1.0 cm(2) V(-1) s(-1)) and fast operating speeds (about 1 ms) at low operating voltages. The devices were extremely light (2 g m(-2)) and exhibited excellent mechanical stability. The devices remained operational even under 50% compressive strain without significant changes in their performance. These results represent significant progress in the fabrication of fully printed organic thin-film transistor devices and circuits for use in unobtrusive electronic applications such as wearable sensors.