Self-propelled microjet engines (microbots) can transport multiple cells into specific locations in a fluid. The motion is externally controlled by a magnetic field which allows to selectively load, ...transport and deliver the cells.
We describe the motion of self-propelled hybrid microengines containing catalase enzyme covalently bound to the cavity of rolled-up microtubes. The high efficiency of these hybrid microengines allows ...them to move at a very low concentration of peroxide fuel. The dynamics of the catalytic engines is mediated by the generation of front-side bubbles, which increase the drag force and make them turn. The specific modification of the inner layer of microtubes with biomolecules can lead to other configurations to generate motion from different chemical fuels.
Strain‐engineered microtubes with an inner catalytic surface serve as self‐propelled microjet engines with speeds of up to ≈2 mm s−1 (approximately 50 body lengths per second). The motion of the ...microjets is caused by gas bubbles ejecting from one opening of the tube, and the velocity can be well approximated by the product of the bubble radius and the bubble ejection frequency. Trajectories of various different geometries are well visualized by long microbubble tails. If a magnetic layer is integrated into the wall of the microjet engine, we can control and localize the trajectories by applying external rotating magnetic fields. Fluid (i.e., fuel) pumping through the microtubes is revealed and directly clarifies the working principle of the catalytic microjet engines.
Strain‐engineered microtubes with an inner catalytic surface serve as self‐propelled catalytic microjet engines, with speeds of up to ≈2 mm s−1 (approximately 50 body lengths per second), and travel along various trajectories that are well‐visualized by long microbubble tails (see image).
Fused silica glass is a material of choice for micromechanical, microfluidic, and optical devices due to its chemical resistance, optical, electrical, and mechanical performance. Wet etching is the ...key method for fabricating of such microdevices. Protective mask integrity is a big challenge due extremely aggressive properties of etching solution. Here, we propose multilevel microstructures fabrication route based on fused silica deep etching through a stepped mask. First, we provide an analysis of a fused silica dissolution mechanism in buffered oxide etching (BOE) solution and calculate the main fluoride fractions like Formula: see text, Formula: see text, Formula: see text as a function of pH and NH
F:HF ratio. Then, we experimentally investigate the influence of BOE composition (1:1-14:1) on the mask resistance, etch rate and profile isotropy during deep etching through a metal/photoresist mask. Finally, we demonstrate a high-quality multilevel over-200 μm etching process with the rate up to 3 μm/min, which could be of a great interest for advanced microdevices with flexure suspensions, inertial masses, microchannels, and through-wafer holes.
We describe the motion of self-propelled catalytic Ti/Fe/Pt rolled-up microtubes (microbots) in the microchannels of a microfluidics system. Their motion is precisely controlled by a small magnetic ...field, and the transport of multiple spherical microparticles into desired locations is achieved. The microbots are powerful enough to propel themselves against flowing streams. The integration of “smart and powerful” microbots into microchip systems can lead to multiple lab-on-a-chip functions such as separation of cells and biosensing.
We have developed a generic approach to engineer tubular micro‐/nanostructures out of many different materials (see figure) with tunable diameters and lengths by precisely releasing and rolling up ...functional nanomembranes on polymers. The technology spans across different scientific fields ranging from photonics to biophysics and we demonstrate optical ring resonators, magneto‐fluidic sensors, remotely controlled microjets and 2D confined channels for cell growth guiding.
Silica ceramics with the open porosity of 10% was infiltrated with the methyl-phenyl-spirocyclosiloxanol (MPS) acetone solution. Various MPS concentrations in the range of 0.1–100% were used. ...Infiltration was followed by the polyfunctional condensation in order to obtain ceramics filled with various volume fractions of the polymethyl-phenyl-spirocyclosiloxane (PMPS). Water absorption capacity, flexural strength, dilatometric thermal expansion, optical and structural properties of the obtained materials were analyzed. As a result, water absorption capacity was less than 0.15% in the range of 1–100% MPS fraction in the initial solution, whereas the flexural strength showed logarithmic growth in the range of 45–63 MPa with MPS fractional increase. In comparison to the initial ceramics, thermal expansion demonstrated several features that can be related to phase transitions and thermal-oxidative degradation of the polymer. Structural properties were analyzed by mercury and gas porometry and scattering techniques. The mean size of pores, that stay unfilled after infiltration, was shown to rise with the polymer fractional volume increase. The obtained results indicate that a relatively low fraction of approximately 1% of the MPS in the initial solution allows to obtain silica ceramics with low water absorption capacity and sufficient flexural strength. It might be attributed to the polymer tendency to fill mostly pore throats.
Light-Controlled Propulsion of Catalytic Microengines Solovev, Alexander A.; Smith, Elliot J.; Bof ' Bufon, Carlos C. ...
Angewandte Chemie (International ed.),
November 11, 2011, Letnik:
50, Številka:
46
Journal Article
Recenzirano
Turn off the light: A white‐light source is used to control the propulsion of catalytic microengines powered by the local decomposition of hydrogen peroxide into oxygen and water. The influence of ...the wavelength of the light and intensity on the fuel conditions provides a remote control over the power of the self‐propelled microengines (see picture).
Compositional engineering of the optical properties of hybrid organic–inorganic lead halide perovskites is crucial for the realization of efficient solar cells and light-emitting devices. We study ...the effect of band gap fluctuations on coherent exciton dynamics in a mixed FA0.9Cs0.1PbI2.8Br0.2 perovskite crystal by using photon echo spectroscopy. We reveal a narrow homogeneous exciton line width of 16 μeV at a temperature of 1.5 K. The corresponding exciton coherence time T 2 = 83 ps is exceptionally long due to the localization of excitons at the scale of tens to hundreds of nanometers. From spectral and temperature dependences of the two- and three-pulse photon echo decay, we conclude that for low-energy excitons pure decoherence associated with elastic scattering on phonons is comparable with the exciton lifetime, while for excitons with higher energies, inelastic scattering to lower energy states via phonon emission dominates.
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