Institute for Integrative Nanosciences (IIN)
The Institute for Integrative Nanosciences IIN was founded on 1st March 2007. About 70-80 scientists and staff members originating from more than ten different nations carry out research both at our main location in Dresden but also at our research site in Chemnitz which was founded two years later in 2009. Research activities at the IIN cover a wealth of modern topics in the Nanosciences ranging from flexible electronics to micro-/nanoscale robotics.
The most important inventions from the IIN include flexible and printable magnetoelectronic devices, the smallest men-made jet engines, self-propelled nanotools, strain tunable single photon devices, lab-in-a-tube systems and ultra-compact self-wound batteries.
Most recent highlights:
Large-area rolled-up nanomembrane capacitor arrays
Miniaturization of electronic devices and reduction of their footprint areas are essential ingredients towards efficient development of energy autonomous systems and electronic circuitry. We demonstrate the feasibility of fabricating ultracompact energy storage elements employing rolled-up nanotechnology. These elements highlight the flexibility and high yield of the parallel fabrication process, which results in a substantial reduction in the device dimensions and better integration of the devices into future miniaturized electronic systems.
Impedemetric sensing of ionic fluids and single cells in a single microtube
Ultracompact three-dimensional tubular structures integrating Au-based electrodes serve as impedimetric microsensors for the in-flow determination of mono- and divalent ionic species and HeLa cells. The microsensors show a two orders of magnitude improved performance over conventional planar conductivity detection systems integrated in micro fluidic platforms and the capability to detect single HeLa cells. These highly integrated conductivity tubular sensors open new possibilities towards lab-in-a-tube devices for bioapplications such as biosensing and bioelectronics.
Cell devision in microtubes
We use micropatterning and strain engineering to encapsulate single living mammalian cells into transparent tubular architectures consisting of 3D rolled-up nanomembranes. The spatial confinement of mitotic mammalian cells inside tubular architectures can perturb metaphase plate formation, delay mitotic progression, and cause chromosomal instability in both a transformed and nontransformed human cell line. These findings could provide important clues into how spatial constraints dictate cellular behavior and function. This work was carried out in collaboration with the University of Cambridge in the UK, the Max-Planck-Institute for Intelligent Systems in Germany and the Johns Hopkins University in the US.
Flexible thermoresponsive microjets
Flexible self-propelled microjets are formed by temperature-induced folding of thin polymer films into microtubes that contain an inner platinum layer for catalytic bubble propulsion in hydrogen peroxide. The polymer films are bilayers of an active and a passive component, which cause the microjets to fold and unfold reversibly by applying slight temperature changes. The speed control by shaping the polymeric Pt films offers a unique approach to operate this new kind of flexible bubble-propelled micromotors. This work was carried out in collaboration with the Leibniz Institute of Polymer Research Dresden, the TU Dresden and the Max-Planck-Institute for Intelligent Systems in Stuttgart.
A sperm driven micro-bio-robot
A new biohybrid micro-robot is developed by capturing bovine sperm cells inside ferromagnetic microtubes that use the motile cells as driving force. These micro-bio-robots can be remotely controlled by an external magnetic field. The performance of micro-robots is described in dependence on tube radius, cell penetration and temperature. The combination of a biological power source and a microdevice is a compelling approach to the development of new microrobotic devices with fascinating future applications such as in-vivo artificial fertilization.
This work was highlighted in:
- news.discovery.com (January 2014) URL
- Phys.org (January 2014) URL
- Deutschlandfunk (January 2014) URL
- Gizmag (January 2014) URL
- FOX News (December 2013) URL
- Science for the Curious Discover (December 2013) URL
- The Independent (December 2013) URL
- New Scientist (December 2013) URL
- Vice Media Inc. (December 2013) URL
- Le figaro - fr (December 2013) URL
- FierceDrugDelivery (December 2013) URL
- Tech Times (December 2013) URL
Domain patterns of magnetic rolled-up microtubes
Rolled-up magnetic microtubes display spiral-like, longitudinally or azimuthally magnetized domain patterns. The rolled-up geometry offers an elegant possibility for tailoring the fundamental magnetic interactions at the nanoscale in three-dimensions. The novel magnetic-domain patterns have a strong impact on their magnetic response and transport properties and could be attractive for future magnetoimpedance-based field sensors.
A wavelength-tunable single-photon emitting diode
The first all-electrically operated wavelength-tunable single-photon source is demonstrated. The device consists of an ultra-thin light-emitting diode containing self-assembled quantum dots integrated onto a piezoelectric crystal.Triggered single photons are generated via injection of short electrical pulses at operation speeds up to 0.8 GHz. The wavelength of the emitted single-photons can be tuned over a broad range by the strain field from the piezoelectric crystal.Our work provides exciting perspectives towards high data rate quantum communications relying on remote electrically-driven single-photon sources.
Stretching quantum dots till they become light
We demonstrate the creation of a light-hole exciton ground state by applying elastic stress to an initially unstrained quantum dot. The signature is clearly distinct from that of the well-known heavy-hole exciton and consists of three orthogonally polarized bright optical transitions and a fine-structure splitting of hundreds of microelectron volts between in-plane and out-of-plane components. Our work paves the way for the exploration of the fundamental properties of three-dimensionally confined light-hole states in quantum technologies and was carried out in collaboration with the Johannes Kepler Universität in Linz, the Kavli Institute at the TU Delft and the Max-Planck Institute for Solid State Research in Stuttgart.
Y.H. Huo et al., Nat. Phys. 10, 46 (2014) URL PDF
This work was highlighted in:
Multichannel anodes for lithium-ion batteries
We employed rolled-up nanotechnology to fabricate sandwich-stacked SnO2/Cu hybrid nanosheets as multichannel anodes for lithium-ion batteries with the use of carbon black as inter-sheet spacer. The sandwich-stacked SnO2/Cu hybrid nanosheets exhibit significant improvement in cyclability compared to SnO2 nanosheets and SnO2/Cu hybrid nanosheets. By employing a direct self-rolling and compressing approach, a much higher effective volume efficiency is achieved as compared to rolled-up hollow tubes. This synthesis approach presents a promising route to design multichannel anodes for high performance Li-ion batteries.
Vertical add-drop filter made from a rolled-up ring resonator
A significant step towards integrated vertically rolled-up microcavities is demonstrated by interfacing SiO2 microtube optical ring resonators with tapered fibers. In this transmission configuration, resonant filtering of optical signals at telecommunication wavelengths is shown in subwavelength thick walled microcavities. Moreover, we present a four-port add-drop filter based on a lifted doubly interfaced vertically rolled-up microcavity. Our work opens opportunities for vertical resonant light transfer in 3D multi-level optical data processing as well as for massively parallel optofluidic analysis of biomaterials in lab-on-a-chip systems.
S. Böttner et al., Appl. Phys. Lett. 102, 251119 (2013) URL PDF
Chemotactic behaviour of artificial engines
When man-made self-powered micromotors swim in a gradient of chemical fuel, they experience a chemical attraction towards the fuel and deviate from their otherwise random motion. We now report that self-propelled microjets and microparticles change their trajectory when hydrogen peroxide fuel is added to the solution in which they navigate, a response similar to the chemotactic behavior of some living organisms.
Diamond lattice photonic crystals from rolled-up membranes
A novel method for the fabrication of diamond lattice photonic crystals by rolling strained pre-patterned titania membranes is proposed. Using rolled-up nanotechnology, full band gap and highly customizable partial band gap photonic crystals are possible. A combination of finite element analysis and band structure calculations of our proposed system shows that photonic crystal bending negligibly influences the band gap, and that at least six windings are necessary. These findings motivate further efforts towards the fabrication of rolled-up photonic crystals.
M. R. Jorgensen et al., Phys. Rev. A. 87, 041803 (2013) URL PDF
Dynamic molecular processes detected by nanomembrane based microtube cavities
Dynamic molecular processes of water and ethanol are detected on the surface of rolled-up opto-chemical microtube resonators. Based on perturbation theory, quantitative information about structural changes in molecular layers are acquired. A robust ice-like H2O molecular layer on the microtube surface was revealed through detecting molecular interactions at room temperature. The ability of the self-assembled microtube cavities to probe molecular changes on the sensing surface constitutes a versatile platform for the detection of diverse surface phenomena in a label-free fashion.
L. B. Ma et al., Adv. Mater. 25, 2357 (2013). URL PDF
New battery research: rolled-up trilayer nanomembranes improve durability and lifetime
We report a new type of tubular configuration made from naturally rolled-up C/Si/C trilayer nanomembranes. A high capacity of ~2000 mAh g-1 can be retained at a current density of 50 mA g-1 without discernible decay, and the capacity can keep ~1000 mAh g-1 even after 300 cycles at 500 mA g-1 with almost 100% capacity retention. The trilayer structure design provides a stable conductive network and prevents Si pulverization and aggregation during cycling, thus guaranteeing superior electrochemical performance.
Rolled-up field effect transistors
We fabricate inorganic thin film transistors with bending radii of less than 5μm maintaining their high electronic performance with on-off ratios of more than 100.000 and subthreshold swings of 160mV/dec. The fabrication technology relies on the roll-up of highly strained semiconducting nanomembranes, which compacts planar transistors into three-dimensional tubular architectures. The rolled-up transistors are perfectly embedded into the wall of a cylindrical fluidic channel, which may boost the performance of large-scale integrated microfluidics to a level way beyond of what is currently available.
Rolling their own for energy storage devices
We report a novel hybrid tubular structure composed of multilayer Ge and Ti nanomembranes with superior reversible capacity by rolled-up nanotech. The intrinsic strain accommodated in the Ge/Ti bilayer nanomembranes is efficiently released by a self-rolling process that thus offers a minimization of the whole system energy. The high conductivity, fast lithium ion diffusion and good volume tolerance of the material are evaluated by single tube devices. The proof of concept in this work paves the way for integration of microbatteries for chip-scale applications.
This work was highlighted in:
Renewable Energy (May, 2013) URL
Stretchable magnetoelectronic devices are demonstrated for the first time. We fabricated GMR multilayers as well as spin valves on free-standing elastic Poly(dimethylsiloxane) (PDMS) membranes. The GMR performance of the sensors on rigid silicon and on free-standing PDMS is similar and does not change with tensile deformations of up to 29% revealing a top sensitivity of 0.8 %/Oe in a magnetic field of 12 Oe. Stretchable magnetoelectronics generates a new quality to modern interactive application fields like smart skin and flexible consumer electronics equipped with magnetic functionalities.
M. Melzer et al., Adv. Mater. 24, 6468 (2012) URL PDF
M. Melzer et al., Nano Lett. 11, 2522 (2011) URL PDF
This work was highlighted in:
Advances in Engineering (April 22, 2013) URL
Making quantum dots electronically symmetric
The lack of structural symmetry which usually characterizes semiconductor quantum dots lifts the energetic degeneracy of the bright excitonic states and hampers severely their use as high-fidelity sources of entangled photons. We demonstrate experimentally and theoretically that it is always possible to restore the excitonic degeneracy by the simultaneous application of large strain and electric fields. This is achieved by using one external perturbation to align the polarization of the exciton emission along the axis of the second perturbation, which then erases completely the energy splitting of the states. This result, which holds for any quantum dot structure, highlights the potential of combining complementary external fields to create artificial atoms meeting the stringent requirements posed by scalable semiconductor-based quantum technology.
This work was chosen as PRL Editors' suggestion and selected for a Viewpoint in Physics (October 1, 2012) URL
Self - Elongating Nanowires
We report the self-assembled growth of Ge nanowires with a height of only 3 unit cells and a length of up to 2 micrometers by means of molecular beam epitaxy. Compared to nanowires grown by catalytic methods, the catalyst-free Ge nanowires we obtained exhibit an outstanding uniformity in their lateral size, they lie horizontally along well-defined crystallographic directions, and they are monolithically integrated into the silicon substrate. In view of their exceptionally small and self-defined cross section, these Ge wires hold promise for the realization of hole systems with exotic properties and provide a new development route for silicon-based nanoelectronics.
This work has been highlighted in:
Magnetically capped rolled-up nanomembranes
In this work, we address curvature-driven modifications of magnetic properties in confined cylindrically curved magnetic nanomembranes. The curved architectures are prepared by capping non-magnetic micrometer- and nanometer-sized rolled-up membranes with a soft-magnetic 20 nm thick permalloy (Ni80Fe20) film. Due to the curvature-driven thickness gradient in magnetic nanostructures, magnetic stray field merely exists at the longitudinal edges of the cap. The corresponding anisotropy of magnetostatic interaction (along with respect to across the cylindrical cap) allows to reduce interaction between neighboring magnetic nanostructures still preserving vortex state, which is a bottleneck of planar stripes. Thus, a much higher areal density of magnetic wires compared to planar stripes might be achieved, which is beneficial to increase storage density of racetrack memory devices.
We fabricated the first printable magnetic sensor that relies on the giant magnetoresistance effect (GMR). The magnetic ink can be painted on virtually any substrate such as paper, polymers, ceramics, glass and exhibits a room-temperature GMR of up to 8%. The performance of a printable GMR sensor is demonstrated by integration into a hybrid electronic circuit produced on the paper of a postcard. The operation of a light emitting diode (LED) is triggered by a permanent magnet that modifies the resistance of the printable magnetic sensor and alters the current flow through the LED. Our demonstrator with a magnetic switch printed on a postcard suggests paves the way for interactive and fully printable electronics.
This work was highlighted in:
- Nanowerk (July 19, 2012) URL PDF
- Spectrum IEEE (July 20, 2012) URL PDF
- Bild (August 29, 2012) URL PDF
- Pro-physik (August 29, 2012) URL PDF
- Uni aktuell at TU Chemnitz (August 29, 2012) URL PDF
- Wissenschaftler (August 31, 2012) URL PDF
- PREVIEW Event & Communication (September 3, 2012) URL PDF
- Wissenschaft Aktuel (September 4, 2012) URL
- Paper of the month: The Latest Science (September 3, 2012)
- Advances in Engineering (April 16, 2013) URL
Two ERC grants for Dr. Denys Makarov and Dr. Samuel Sanchez
Congratulations to Denys Makarov and Samuel Sanchez - each of them securing an ERC "Starting Grant" worth 1.5Mio Eur for their projects "Shapeable Magnetoelectronics in Research and Technology" and "Lab-in-a-tube and Nanorobotic biosensors", respectively. Both awarded projects are groundbreaking and open entirely new fields in nanomembrane technologies.
On-chip integration of rolled-up ring resonators as label-free optofluidic sensors
We demonstrate fully integrated rolled-up optofluidic ring resonators (RU-OFRRs) based on glass SiO2 material with high quality factors of up to 2900. The microfluidic integration of several RU-OFRRs on one chip is solved by enclosing the microtubes with a patterned robust SU-8 polymeric matrix. A viewport on each microtube enables exact excitation and monitoring of whispering gallery modes under constant ambient conditions, while exchanging the content of the RU-OFRR with liquids of different refractive indices. The sensitivity of the integrated RU-OFRR, which is the response of the modes to the change in refractive index of the liquid, is up to 880 nm/refractive index units.
A lab-in-a-tube device comprises numerous ultracompact components in a single tube which can be developed using rolled-up technology. A single device, being one of thousands in the on-chip system, would be independently capable of stimulating, monitoring and investigating individual organisms.
Engineering the properties of Quantum-Light-Emitting Diodes by strain
We present the first nanomembrane Quantum-Light-Emitting Diodes (QLEDs) integrated onto piezoelectric actuators. We demonstrate that the large strain fields provided by the piezoelectric actuators can be used to engineer the whole emission properties of the quantum emitters (semiconductor quantum dots) without degrading the electrical injection operation of standard QLEDs. The hybrid device presented here has the potential to form the basis of scalable electrically-driven sources for quantum communication.
Tunable generation of correlated vortices in open superconductor tubes
We theoretically apply transport currents and magnetic fields to open superconducting tubes. In such tubes, which can be created by rolled-up nanotech, vortices nucleate periodically at one edge of the tube, subsequently move along the tube axis under the action of the Lorentz force and denucleate at the opposite edge of the tube. The characteristic times of the vortex motions are efficiently controlled by the tube radius and are significantly different to the situation in a planar film under the same magnetic field. Our results open perspectives towards tailoring non-equilibrium properties of vortices and their application as tunable superconducting flux generators for fluxon-based information technologies.
*click on pictures to see animation
Elastic magnetic sensor with isotropic sensitivity for in-flow detection of magnetic objects
We present a conceptually new approach for the detection of magnetic objects flowing through a fluidic channel. We produce an elastic and stretchable magnetic sensor and wrap it around a capillary tubing. Thus, the stray fields induced by the flowing magnetic objects can be detected virtually in all directions (isotropic sensitivity), which is unique for the elastic sensor compared to rigid planar counterparts. In combination with magnetic particles as biomarkers, this elastic magnetic sensor can be considered as a new generation of biosensors for cells or even biomolecules evading many difficulties of traditional optical detection methods like low speed, excitation, bulky and expensive equipment, biomolecular amplification and the need for transparent packaging.
Self-propelled nanotools drilling into cells
We design nanoscale tools in the form of autonomous and remotely guided catalytically self-propelled rolled-up tubes. If these tubes are rolled-up in an asymmetric fashion they move in a corkscrew-like trajectory and rotate with high frequency around their own axis. This rotating motion allows them to drill into cell material (here: fixed HeLa cells). Since they can be remotely controlled by an external magnetic field, deliberate non-invasive nano-surgery might become reality in the far future.
Fabrication and applications of large arrays of multifunctional rolled-up SiO/SiO2 microtubes
Biocompatible, multifunctional large arrays of transparent SiO/SiO2 microtubes are fabricated by rolled-up nanotech. The outer tubular diameter as a function of thicknesses of SiO and SiO2has been systematically studied and the roll-up parameters have been optimized to deterministically achieve a yield of nearly 100%. A macroscopic continuum mechanical model is in good agreement with the experimental data. The relative ease in functionalization of the “glass” microtubes with different biomaterials renders rolled-up nanotech an excellent option for various on- and off-chip applications, including optofluidic sensors, micro-engines and pre-patterned 3D scaffolds for cell culturing.
This work was selected as a hot article by the journal.
Spin selective tunneling through SiGe quantum dots
When contacting a quantum dot (QD) with normal metallic leads no spin selective tunnel rates are expected. However, low-temperature magneto-transport measurements through individual SiGe self-assembled QDs have now revealed that this assumption is not always true. Indeed, we have observed that spin-selective tunnel rates through individual QDs can be achieved with normal metallic contacts. The surprising spin selectivity arises from the interplay of the orbital effect of the magnetic field with the strong spin-orbit interaction present in the valence band of the semiconductor. This work was carried out in collaboration with CEA-Grenoble and Yale University.
Working towards creating a fully functional Lab-in-a-tube, we report a method for the precise capturing of embryonic fibroblast mouse cells into rolled-up microtube resonators. The microtubes contain a nanometer-sized gap in their wall which defines a new type of optofluidic sensor, i.e., a flexible split-wall microtube resonator sensor (F-SWμRS), employed as a label-free fully integrative detection tool for individual cells. The sensor action works through peak sharpening and spectral shifts of whispering gallery modes within the microresonators under light illumination.
This work was highlighted in:
Lab Chip 12, 503 (2012) URL
"Starting" and "stopping" microjet engines
The control over the autonomous motion of artificial nano/micromachines is essential for real biomedical and nanotechnological applications. Consequently, a complete nanomachine should be able to be turned on and off at will. We report the tuning of the propulsion power of catalytic microjets through illumination of a solution by a white-light source. We show that light suppresses the generation of microbubbles, stopping the engines if they are fixed-to or self-propelled above a platinum-patterned surface. The microjets are reactivated by dimming the light source that illuminates the fuel solution.
Magnetic microhelix coil structures
We design and investigate three-dimensional microhelix coil structures that are radial-, corkscrew-, and hollow-bar-magnetized. The magnetization configurations of the differently magnetized coils are experimentally revealed by probing their specific dynamic response to an external magnetic field. Helix coils offer an opportunity to realize microscale geometries of the magnetic toroidal moment, observed so far only in bulk multiferroic materials.
Rolled-up magnetic sensor for in-flow detection of magnetic objects
Rolled-up nanotech is used to fabricate magnetic sensor devices, which are directly integrated into fluidic architectures. Strain engineering is applied to roll-up a thin layer stack revealing giant magnetoresistence (GMR). In this way, the rolled-up tube acts as a fluidic channel, while the integrated GMR sensor responds to a magnetic field. In-flow detection of ferromagnetic CrO2 nanoparticles embedded in a biocompatible polymeric hydrogel shell is highlighted. The advantage of rolled-up devices is their integrability into existing on-chip technologies and the ability to combine several functions into a single architecture, possibly leading to a fully operational lab-in-a-tube system.
Superfast motion of catalytic microjet engines at physiological temperature
We reduced the toxicity of the fuel used to self-propel artificial nanomachines. At physiological temperatures, i.e. 37°C, only very small amounts of H2O2 as fuel is needed to propel the microjets. Under those conditions, Fibroblast cells are viable for more than 1 hour which is highly important for the not-too-distant use of artificial nanomachines in biomedical applications. In addition, at 5% H2O2, the microjets acquire superfast speeds reaching 10 mm sec-1. The dynamics of motion is altered while increasing the speed, i.e. the motion deviates from the linear to curvilinear trajectories which has been theoretically modelled.
This work was highlighted in:
New Scientist, 2832 (2011) (Oct 2, 2011) URL
Hybrid organic/inorganic molecular heterojunctions
We combine self-assembly and top-down methods to create hybrid junctions consisting of single organic molecular monolayers sandwiched between metal and/or single-crystalline semiconductor nanomembrane based electrodes. The fabrication process is fully integrative and produces a yield loss of less than 5% on-chip. The nanomembrane-based electrodes guarantee a soft yet robust contact to the molecules where the presence of pinholes and other defects becomes almost irrelevant. We also pioneer the fabrication and characterization of semiconductor/molecule/semiconductor tunneling heterojunctions which exhibit a double transition from direct tunneling to field emission and back to direct tunneling, a phenomenon which has not been reported previously.
This work was highlighted in:
Nature Materials, 10, 724 (2011) (Sep 23, 2011) URL
Towards remotely controlled intelligent microrobots
In this tutorial review we describe recent progress on catalytic microtubular engines fabricated by rolled-up nanotech. The control over speed, directionality and interactions of the microengines to perform tasks such as cargo transportation is also discussed. Since rolled-up nanotech on polymers can easily integrate almost any type of inorganic material, huge potential and advanced performance such as high speed, cargo delivery, motion control, and dynamic assembly are foreseen-ultimately promising a practical way to construct versatile and intelligent catalytic tubular microrobots.
This work was highlighted in:
Slowing down single photons from quantum dots
Nowadays, the vast majority of information is transferred by light in optical fibers. The single elementary particle of light is called a photon. The advantage of single photons is that they can carry and transfer quantum information over very long distances, enabling 100% secure communication, impossible to crack. We have successfully designed a new type of semiconductor material (quantum dots), which emit photons at a frequency that can be combined with rubidium atoms. By guiding the emitted light through the atoms the speed of the photons is reduced to less than 4% of the speed of light in vacuum. The breakthrough can enable the realization of quantum memories - an essential component in quantum information technology. Merging semiconductor and atomic physics in a hybrid interface opens the way to a series of novel experiments and research directions. For instance, quantum memories and quantum repeaters for quantum dot generated photons can now be fabricated. This work was carried out in close collaboration with the Kavli Institute of Nanoscience at Delft University of Technology in the Netherlands.
Guinness World Record® for "Smallest Man-Made Jet Engine"
"The smallest man-made jet engine measures just 600nm across and weighs 1 picogram. It was produced by Alex A. Solovev, Samuel Sanchez, Yongfeng Mei and Oliver G. Schmidt at the Leibniz Institute for Solid State and Materials Research (IFW Dresden)."
This is the text of the official certificate issued by Guinness World Records® beginning of this year (see left side for scanned original).
This achievement was highlighted in:
- Pro-Physik.de (March 8, 2011) URL
- Die Welt (March 8, 2011) URL
- Scinexx (March 9, 2011) URL
- Nanowerk (March 9, 2011) URL
Barkhausen Poster Award 2010 goes to IIN
Congratulations to Michael Melzer, who has been awarded this year's Barkhausen Poster Prize on 4 February 2011!
On his poster he described in detail how to fabricate highly sensitive thin films to detect small magnetic fields on rubber substrates. His work paves the way for a technology rapidly moving towards stretchable and flexible magnetoelelctronics. An electronic version of the poster can be found here.
The Barkhausen Poster Prize is awarded every year to students and young scientists for their outstanding research and convincing presentation. The award is funded by Materialforschungsverbund Dresden, TU Dresden, European Center for Micro- and Nanoreliability and Fries Research & Technology.
Microbots swimming in the flowing streams of microfluidic channels
The motion of artificial catalytic nanomachines is commonly studied in free bulk solution, which differs significantly from the stream-like channel networks existing in the human body. Here, we demonstrate that catalytic microbots can self-propel in the microchannels of a microfluidics system and transport multiple spherical microparticles into desired locations. We also show for the first time that artificial micromachines can easily swim against strong flowing streams.The integration of “smart and powerful” microbots with microchips will lead to plentiful functions in lab-on-a-chip devices including e.g. efficient and convenient drug or cell separation.
Cardboard rolls on the nanoscale
Everybody knows that cardboard paper can be a highly anisotropic material. You can easily bend or roll it in one direction and it is stiff in the other. If you take a close look you will find that the paper is periodically buckled along one direction. We have now exploited this phenomenon on the nanoscale to define the roll-up direction of ultra-thin membranes on a substrate surface. Given the abundance of fabrication methods to create thin corrugated films (including graphene), our work will help to realize novel 3D tubular nanostructures with well-controlled position, orientation, material composition, and exciting functionalities.