Force-Controlled Fluidic Injection into Single Cell Nuclei

1. Orane Guillaume-Gentil¹, 
2. Eva Potthoff¹,
3. Dario Ossola², 
4. Pablo Dörig², 
5. Tomaso Zambelli^2,*, 
6. Julia A. Vorholt^1,*

Article first published online: 20 NOV 2012

DOI: 10.1002/smll.201202276

urpassing the physical barriers of the cytoplasmic and nuclear membranes to deliver biomolecules directly into cell nuclei offers opportunities to investigate dynamic processes in living cells. The potential of atomic force microscopy coupled to microfluidics (FluidFM) for volume-controlled intranuclear delivery is demonstrated, whereby minimally invasive microchanneled probes are remotely driven with high spatiotemporal resolution.

Giant-Amplitude, High-Work Density Microactuators with Phase Transition Activated Nanolayer Bimorphs

Kai Liu †‡, Chun Cheng †, Zhenting Cheng §, Kevin Wang †‡, Ramamoorthy Ramesh †‡, and Junqiao Wu*†‡

^† Department of Materials Science and Engineering,University of California, Berkeley, California 94720, United States

^‡ Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States

^§ Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, California 94720, United States

Nano Lett., Article ASAP

DOI: 10.1021/nl303405g

Publication Date (Web): November 16, 2012

Copyright © 2012 American Chemical Society

Various mechanisms are currently exploited to transduce a wide range of stimulating sources into mechanical motion. At the microscale, simultaneously high amplitude, high work output, and high speed in actuation are hindered by limitations of these actuation mechanisms. Here we demonstrate a set of microactuators fabricated by a simple microfabrication process, showing simultaneously high performance by these metrics, operated on the structural phase transition in vanadium dioxide responding to diverse stimuli of heat, electric current, and light. In both ambient and aqueous conditions, the actuators bend with exceedingly high displacement-to-length ratios up to 1 in the sub-100 μm length scale, work densities over 0.63 J/cm³, and at frequencies up to 6 kHz. The functionalities of actuation can be further enriched with integrated designs of planar as well as three-dimensional geometries. Combining the superior performance, high durability, diversity in responsive stimuli, versatile working environments, and microscale manufacturability, these actuators offer potential applications in microelectromechanical systems, microfluidics, robotics, drug delivery, and artificial muscles.

Characterizing the Lateral Friction of Nanoparticles on On-Chip Integrated Black Lipid Membranes

1. Tianhong Chen, 
2. Björn M. Reinhard^*

Article first published online: 23 NOV 2012

DOI: 10.1002/smll.201202005

The use of nanoparticles (NPs) in biomedical applications creates a need for appropriate model systems to systematically investigate NP–membrane interactions under well-defined conditions. Black lipid membranes (BLMs) are free-floating membranes with defined composition that are ideally suited for characterizing NP–membrane interactions free of any potential perturbation through a supporting substrate. Herein, arrays of microfabricated BLMs are integrated into a chip-based platform that is compatible with high-speed optical NP tracking. This system is used to investigate the lateral diffusion of 40 nm gold spheres tethered to biotinylated lipids through antibody-functionalized ligands (single-stranded DNA or polyethylene glycol). Although the NPs show an almost free and ergodic diffusion, their lateral motion is subject to substantial drag at the membrane surface, which leads to systematically smaller diffusion coefficients than those obtained for lipids in the membrane through fluorescence recovery after photobleaching. The lateral mobility of the NPs is influenced by the chemical composition and salt concentration at the NP-membrane interface, but is independent of the ligand density in the membrane. Together with the observation that nanoprisms, which have a larger relative contact area with the membrane than spherical NPs, show an even slower diffusion, these findings indicate that the lateral mobility of NPs tethered in close vicinity to a membrane is significantly reduced by the friction at the NP-membrane interface.

Microscopic Rates of Peptide–Phospholipid Bilayer Interactions from Single-Molecule Residence Times

Grant A. Myers †, Daniel A. Gacek †, Eric M. Peterson†, Christopher B. Fox †‡, and Joel M. Harris *†‡

^† Department of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, Utah 84112-0850, United States

^‡ Department of Bioengineering, University of Utah, 50 South Central Campus Drive, Salt Lake City, Utah 84112-9202, United States

J. Am. Chem. Soc., Article ASAP

DOI: 10.1021/ja306074k

Publication Date (Web): November 14, 201

The binding of glucagon-like peptide-1 (GLP-1) to a planar phospholipid bilayer is measured using single-molecule total internal reflection fluorescence microscopy. From several reports in the literature, GLP-1 has been shown to be a random coil in free solution, adopting a folded, α-helix conformation when intercalated into membrane environments. Single-molecule fluorescence measurements of GLP-1 binding to supported lipid bilayers show evidence of two populations of membrane-associated molecules having different residence times, suggesting weakly adsorbed peptides and strongly bound peptides in the lipid bilayer. The path to and from a strongly bound (folded, intercalated) state would likely include an adsorbed state as an intermediate, so that the resulting kinetics would correspond to a consecutive first-order reversible three-state model. In this work, the relationships between measured single-molecule residence times and the microscopic rates in a three-state kinetic model are derived and used to interpret the binding of GLP-1 to a supported lipid bilayer. The system of differential equations associated with the proposed consecutive-three state kinetics scheme is solved, and the solution is applied to interpret histograms of single-molecule, GLP-1 residence times in terms of the microscopic rates in the sequential two-step model. These microscopic rates are used to estimate the free energy barrier to adsorption, the fraction of peptides adsorbing to the membrane surface that successfully intercalate in the bilayer, the lifetime of inserted peptides in the membrane, and the free energy change of insertion into the lipid bilayer from the adsorbed state. The transition from a random coil in solution to a folded state in a membrane has been recognized as a common motif for insertion of membrane active peptides. Therefore, the relationships developed here could have wide application to the kinetic analysis of peptide–membrane interactions

Dynamically Self-Assembling Carriers Enable Guiding of Diamagnetic Particles by Weak Magnets

Olga Chovnik , Renata Balgley , Joel R. Goldman , and Rafal Klajn *

Department of Organic Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel

J. Am. Chem. Soc., Article ASAP

DOI: 10.1021/ja309633v

Publication Date (Web): November 26, 2012

Copyright © 2012 American Chemical Society

We show that diamagnetic particles can be remotely manipulated by a magnet by the reversible adsorption of dual-responsive, light-switchable/superparamagnetic nanoparticles down to their surface. Adsorption occurs upon exposure to UV light, and can be reversed thermally or by ambient light. The dynamic self-assembly of thin films of the dual-responsive nanoparticles induces attractive interactions between diamagnetic particles. We demonstrate that catalytic amounts of the dual-responsive nanoparticles are sufficient to magnetically guide and deliver the diamagnetic particles to desired locations, where they can then be released by disassembling the dynamic layers of superparamagnetic nanoparticles with visible light.

Rapid, Controllable Fabrication of Regular Complex Microarchitectures by Capillary Assembly of Micropillars and Their Application in Selectively Trapping/Releasing Microparticles

1. Dong Wu¹, 
2. Si-Zhu Wu¹, 
3. Shuai Zhao¹, 
4. Jia Yao¹, 
5. Jiang-Nan Wang¹, 
6. Qi-Dai Chen^1,*,
7. Hong-Bo Sun^1,2,*

Article first published online: 12 NOV 2012

DOI: 10.1002/smll.201201689

A simple strategy to realize new controllable 3D microstructures and a novel method to reversibly trapping and releasing microparticles are reported. This technique controls the height, shape, width, and arrangement of pillar arrays and realizes a series of special microstructures from 2-pillar-cell to 12 cell arrays, S-shape, chain-shape and triangle 3-cell arrays by a combined top down/bottom up method: laser interference lithography and capillary force-induced assembly. Due to the inherent features of this method, the whole time is less than 3 min and the fabricated area determined by the size of the laser beam can reach as much as 1 cm², which shows this method is very simple, rapid, and high-throughput. It is further demonstrated that the ‘mechanical hand’-like 4-cell arrays could be used to selectively trap/release microparticles with different sizes, e.g., 1.5, 2, or 3.5 μm, which are controlled by the period of the microstructures from 2.5 to 4 μm, and 6 μm. Finally, the ‘mechanical hand’-like 4-cell arrays are integrated into 100 μm-width microfluidic channels prepared by ultraviolet photolithography, which shows that this technique is compatible with conventional microfabrication methods for on-chip applications.

Continuous Microwire Patterns Dominated by Controllable Rupture of Liquid Films

1. Zhiqing Xin^1,2,†, 
2. Bin Su^1,†, 
3. Jianjun Wang¹,
4. Xingye Zhang¹, 
5. Zhiliang Zhang^1,2,
6. Mengmeng Deng^1,2, 
7. Yanlin Song^1,*, 
8. Lei Jiang¹

Article first published online: 15 NOV 2012

DOI: 10.1002/smll.201202515

Controllable microwire patterns are prepared by dominating the rupture of liquid films. Regular rhombic-shaped micropillar arrays serve as wetting defects to pin or depin liquids, yielding continuous, herringbone, bead-shaped polystyrene microwire patterns or bead arrays. The results provide a deeper understanding of the controllable rupture of liquid films and offer a general strategy for the organization of polymers into structures needed for wiring, interconnects, and functional devices for future microfabrication.

Nanoscale Triboelectric-Effect-Enabled Energy Conversion for Sustainably Powering Portable Electronics

Sihong Wang †, Long Lin †, and Zhong Lin Wang †‡*

^† School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0245, United States

^‡ Beijing Institute of Nanoenergy and Nanosystems,Chinese Academy of Sciences, Beijing, China

Nano Lett., Article ASAP

DOI: 10.1021/nl303573d

Publication Date (Web): November 6, 2012

Copyright © 2012 American Chemical Society

Harvesting energy from our living environment is an effective approach for sustainable, maintenance-free, and green power source for wireless, portable, or implanted electronics. Mechanical energy scavenging based on triboelectric effect has been proven to be simple, cost-effective, and robust. However, its output is still insufficient for sustainably driving electronic devices/systems. Here, we demonstrated a rationally designed arch-shaped triboelectric nanogenerator (TENG) by utilizing the contact electrification between a polymer thin film and a metal thin foil. The working mechanism of the TENG was studied by finite element simulation. The output voltage, current density, and energy volume density reached 230 V, 15.5 μA/cm², and 128 mW/cm³, respectively, and an energy conversion efficiency as high as 10–39% has been demonstrated. The TENG was systematically studied and demonstrated as a sustainable power source that can not only drive instantaneous operation of light-emitting diodes (LEDs) but also charge a lithium ion battery as a regulated power module for powering a wireless sensor system and a commercial cell phone, which is the first demonstration of the nanogenerator for driving personal mobile electronics, opening the chapter of impacting general people’s life by nanogenerators.

Three-Dimensionally Engineered Porous Silicon Electrodes for Li Ion Batteries

Sanketh R. Gowda †, Victor Pushparaj ,Subramanya Herle *, G. Girishkumar , Joseph G. Gordon , Hemtej Gullapalli ‡, Xiaobo Zhan ‡,Pulickel M. Ajayan *‡§, and Arava Leela Mohana Reddy *‡

^†Department of Chemical and Biomolecular Engineering,^‡Department of Mechanical Engineering and Materials Science, and ^§Department of ChemistryRice University, Houston, Texas 77005, United States

 Advanced Technology Group, Applied Materials Inc., Santa Clara, California 94085, United States

Nano Lett., Article ASAP

DOI: 10.1021/nl302114j

Publication Date (Web): October 31, 2012

Copyright © 2012 American Chemical Society

The ultimate goal of Li ion battery design should consist of fully accessible metallic current collectors, possibly of nanoscale dimensions, intimately in contact with high capacity stable electrode materials. Here we engineer three-dimensional porous nickel based current collector coated conformally with layers of silicon, which typically suffers from poor cycle life, to form high-capacity electrodes. These binder/conductive additive free silicon electrodes show excellent electrode adhesion resulting in superior cyclic stability and rate capability. The nickel current collector design also allows for an increase in silicon loading per unit area leading to high areal discharge capacities of up to 0.8 mAh/cm² without significant loss in rate capability. An excellent electrode utilization (85%) and improved cyclic stability for the metal/silicon system is attributed to reduced internal stresses/fracture upon electrode expansion during cycling and shorter ionic/electronic diffusion pathways that help in improving the rate capability of thicker silicon layers.

Quantitative Measurement of the Surface Self-Diffusion on Au Nanoparticles by Aberration-Corrected Transmission Electron Microscopy

A. Surrey †‡, D. Pohl †‡, L. Schultz †‡, and B. Rellinghaus *†

^† IFW Dresden, Institute for Metallic Materials, P.O. Box 270116, D-01171 Dresden, Germany

^‡ TU Dresden, Institut für Festkörperphysik, D-01062 Dresden, Germany

Nano Lett., Article ASAP

DOI: 10.1021/nl302280x

Publication Date (Web): November 8, 2012

Copyright © 2012 American Chemical Society

We present a method that allows for a quantitative measurement of the surface self-diffusion on nanostructures, such as nanoparticles, at the atomic scale using aberration-corrected high-resolution transmission electron microscopy (HRTEM). The diffusion coefficient can be estimated by measuring the fluctuation of the atom column occupation at the surface of Au nanoparticles, which is directly observable in temporal sequences of HRTEM images. Both a Au icosahedron and a truncated Au octahedron are investigated, and their diffusion coefficients are found to be in the same order of magnitude, D = 10^–17 to 10^–16cm²/s. It is to be assumed that the measured surface diffusion is affected by the imaging electron beam. This assumption is supported by the observed instability of a (5 × 1) surface reconstruction on a {100} Au facet.

Tug-of-War in Motor Protein Ensembles Revealed with a Programmable DNA Origami Scaffold

1. N. D. Derr¹,²,³,*, 
2. B. S. Goodman¹,*, 
3. R. Jungmann⁴,⁵, 
4. A. E. Leschziner⁶, 
5. W. M. Shih²,³,⁵, 
6. S. L. Reck-Peterson¹,†

Published Online October 11 2012Science 2 November 2012: 
Vol. 338 no. 6107 pp. 662-665 
DOI: 10.1126/science.1226734

Cytoplasmic dynein and kinesin-1 are microtubule-based motors with opposite polarity that transport a wide variety of cargo in eukaryotic cells. Many cellular cargos demonstrate bidirectional movement due to the presence of ensembles of dynein and kinesin, but are ultimately sorted with spatial and temporal precision. To investigate the mechanisms that coordinate motor ensemble behavior, we built a programmable synthetic cargo using three-dimensional DNA origami to which varying numbers of DNA oligonucleotide-linked motors could be attached, allowing for control of motor type, number, spacing, and orientation in vitro. In ensembles of one to seven identical-polarity motors, motor number had minimal affect on directional velocity, whereas ensembles of opposite-polarity motors engaged in a tug-of-war resolvable by disengaging one motor species

Non-invasive imaging through opaque scattering layers

• Jacopo Bertolotti,
• Elbert G. van Putten,
• Christian Blum,
• Ad Lagendijk,
• Willem L. Vos
• &Allard P. Mosk

• Nature

   

  491,

   

  232–234

   

  (08 November 2012)

   

  doi:10.1038/nature11578

  Received

   

  27 July 2012 

  Accepted

   

  12 September 2012 

  Published online

   

  07 November 2012

  
  

  
  
  

  Non-invasive optical imaging techniques, such as optical coherence tomography^1, 2, 3, are essential diagnostic tools in many disciplines, from the life sciences to nanotechnology. However, present methods are not able to image through opaque layers that scatter all the incident light^4, 5. Even a very thin layer of a scattering material can appear opaque and hide any objects behind it⁶. Although great progress has been made recently with methods such as ghost imaging^7, 8 and wavefront shaping^9, 10, 11, present procedures are still invasive because they require either a detector¹² or a nonlinear material¹³ to be placed behind the scattering layer. Here we report an optical method that allows non-invasive imaging of a fluorescent object that is completely hidden behind an opaque scattering layer. We illuminate the object with laser light that has passed through the scattering layer. We scan the angle of incidence of the laser beam and detect the total fluorescence of the object from the front. From the detected signal, we obtain the image of the hidden object using an iterative algorithm^14, 15. As a proof of concept, we retrieve a detailed image of a fluorescent object, comparable in size (50 micrometres) to a typical human cell, hidden 6 millimetres behind an opaque optical diffuser, and an image of a complex biological sample enclosed between two opaque screens. This approach to non-invasive imaging through strongly scattering media can be generalized to other contrast mechanisms and geometries.