L-2L ladder digital-to-analogue converter for dynamics generation of chemical concentrations.

Cellular response to dynamic chemical stimulation encodes rich information about the underlying reaction pathways and their kinetics. Microfluidic chemical stimulators play a key role in generating dynamic concentration waveforms by mixing several aqueous solutions. In this article, we propose a multi-layer microfluidic chemical stimulator capable of modulating chemical concentrations by a simple binary logic based on the electronic-hydraulic analogy of electronic R-2R ladder circuits.

Surface-limited reactions for spatial control of kinesin-microtubule motility assays using indirect irradiation of an electron beam.

Gliding of microtubules (MTs) on kinesins has been applied to lab-on-a-chip devices, which enable autonomous transportation and detection of biomolecules in the field of bioengineering. For rapid fabrication and evaluation of the kinesin-MT based devices, optical control techniques have been developed for control of kinesin activity and density; however, use of caged molecules lacks spatial controllability for long-term experiments, and direct irradiations of UV light onto kinesin-coated surfaces are inherently damaging to MTs due to their depth limit since the heights of the kinesin-MT systems are at the tens of a nanometer scale. Considering surface electric fields in electrolytic solutions are shielded at the nanometer scale due to Debye shielding, in this study, we show that fine spatial control of kinesin density and activity is enabled using surface-limited electrochemical reactions induced by indirect irradiations of an electron beam (EB).

Explicit calculation method for cell alignment in non-circular geometries.

The alignment of spindle-shaped cells in two-dimensional geometries induces singular points called topological defects, at which the alignment angle of the cell cannot be defined. To control defects related to biological roles such as cell apoptosis, calculation methods for predicting the defect positions are required. This study proposes an explicit calculation method for predicting cell alignment and defect positions in non-circular geometries.

Tough, permeable and biocompatible microfluidic devices formed through the buckling delamination of soft hydrogel films.

Microchannels in soft materials play an important role in developing movable, deformable, and biocompatible fluidic systems for applications in various fields. Intensively investigated approaches to create microscale channel architectures use mechanical instability in soft materials, which can provide intricate yet ordered architectures with low cost and high throughput. Here, for microchannel fabrication, we demonstrate the use of swelling-driven buckle delamination of hydrogels, which is a mechanical instability pattern found in compressed film/substrate layer composites.

Dynamic Creation of 3D Hydrogel Architectures via Selective Swelling Programmed by Interfacial Bonding.

The topological features of material surfaces are crucial to the emergence of functions based on characteristic architectures. Among them, the combination of surface architectures and soft materials, which are highly deformable and flexible, has great potential as regards developing functional materials toward providing/enhancing advanced functions such as switchability and variability. Therefore, a simple yet versatile method for creating three-dimensional (3D) architectures based on soft materials is strongly required.

Pause of the target gliding microtuble on the virtual cathode.

We report the transient response of gliding microtubules on a virtual cathode. In vivo activities, microtubule-kinesin systems are known to act as motor proteins with respect to cell motility cytokinesis and cellular transport by hydrolyzing ATP molecules. With development of in vitro assays, motor proteins have been attracting much attention as a key component for highly efficient nano-transportation systems.

Analysing diffusion and flow-driven instability using semidefinite programming.

Diffusion and flow-driven instability, or transport-driven instability, is one of the central mechanisms to generate inhomogeneous gradient of concentrations in spatially distributed chemical systems. However, verifying the transport-driven instability of reaction-diffusion-advection systems requires checking the Jacobian eigenvalues of infinitely many Fourier modes, which is computationally intractable. To overcome this limitation, this paper proposes mathematical optimization algorithms that determine the stability/instability of reaction-diffusion-advection systems by finite steps of algebraic calculations.

Pinpoint Delivery of Molecules by Using Electron Beam Addressing Virtual Cathode Display.

Electroporation, a physical transfection method to introduce genomic molecules in selective living cells, could be implemented by microelectrode devices. A local electric field generated by a finer electrode can induces cytomembrane poration in the electrode vicinity. To employ fine, high-speed scanning electrodes, we developed a fine virtual cathode pattern, which was generated on a cell adhesive surface of 100-nm-thick SiN membrane by inverted-electron beam lithography.

Dynamic electromechanical control of biomolecules using a nano virtual cathode display.

The dynamic electromechanical control of spatial structures of biomolecules in aqueous solutions was demonstrated using a nano virtual cathode display. By generating a focused electric field around the biomolecules using an electron beam (EB), the molecules' spatiotemporal responses to the electrical stimuli, such as globule transition of DNA random coils and deformation of planar lipid bilayers and vesicles, were successfully observed. The proposed system may be applied to high resolution and high degree-of-freedom manipulations to measure the mechanical and structural properties of bio-nanomaterials.

Spatiotemporal Control of Electrokinetic Transport in Nanofluidics Using an Inverted Electron-Beam Lithography System.

Manipulation techniques of biomolecules have been proposed for biochemical analysis which combine electrokinetic dynamics, such as electrophoresis or electroosmotic flow, with optical manipulation to provide high throughput and high spatial degrees of freedom. However, there are still challenging problems in nanoscale manipulation due to the diffraction limit of optics. We propose here a new manipulation technique for spatiotemporal control of chemical transport in nanofluids using an inverted electron-beam (EB) lithography system for liquid samples.