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Department Talks

  • Dr. Dieter Nees
  • https://global.gotomeeting.com/join/588789885

Roll-to-roll UV nanoimprint lithography (R2R-UV-NIL) gains increasing industrial interest for large area nano- and micro-structuring of flexible substrates because it combines nanometer resolution with many square meter per minute productivity. Small-area masters of functional nano and micro surface structures are readily available by various lithographic techniques like e.g. UV-, e-beam- or interference lithography. However, the upscaling of small-area nano- and micro-structured masters into medium size roller molds – often called shims - for R2R-UV-NIL production still remains a bottleneck in the large area nano-structuring process chain. At JR MATERIALS we have installed a customized EVG 770 UV-NIL-stepper and are developing step-&-repeat UV-NIL processes and materials for the seamless upscaling of small-area masters into polymer shims for our R2R-UV-NIL pilot line with dimensions of up to 270 x 630 mm2. These polymer shims can be used either directly for short to medium R2R-UV-NIL manufacturing runs or get galvano-formed into nickel-shims for real long run production. In this seminar the JR MATERIALS UV-NIL tools, processes and materials as well as a few applications will be presented.

Cancelled: Electro-active Ionic Elastomers

  • 23 March 2020 • 11:00—12:00
  • Prof. Antal Jákli
  • 2P04

Motivated by the low voltage driven actuation of ionic Electroactive Polymers (iEAPs) [1] [2], recently we began investigating ionic elastomers. In this talk I will discuss the preparation, physical characterization and electric bending actuation properties of two novel ionic elastomers; ionic polymer electrolyte membranes (iPEM)[3], and ionic liquid crystal elastomers (iLCE).[4] Both materials can be actuated by low frequency AC or DC voltages of less than 1 V. The bending actuation properties of the iPEMs are outperforming most of the well-developed iEAPs, and the not optimized first iLCEs are already comparable to them. Ionic liquid crystal elastomers also exhibit superior features, such as the alignment dependent actuation, which offers the possibility of pre-programed actuation pattern at the level of cross-linking process. Additionally, multiple (thermal, optical and electric) actuations are also possible. I will also discuss issues with compliant electrodes and possible soft robotic applications. [1] Y. Bar-Cohen, Electroactive Polyer Actuators as Artficial Muscles: Reality, Potential and Challenges, SPIE Press, Bellingham, 2004. [2] O. Kim, S. J. Kim, M. J. Park, Chem. Commun. 2018, 54, 4895. [3] C. P. H. Rajapaksha, C. Feng, C. Piedrahita, J. Cao, V. Kaphle, B. Lüssem, T. Kyu, A. Jákli, Macromol. Rapid Commun. 2020, in print. [4] C. Feng, C. P. H. Rajapaksha, J. M. Cedillo, C. Piedrahita, J. Cao, V. Kaphle, B. Lussem, T. Kyu, A. I. Jákli, Macromol. Rapid Commun. 2019, 1900299.

  • Danijela Gregurec, PhD
  • 3P02

In this talk I will discuss the development of functional materials and their application in modulating the biological microenvironment during cellular sensing and signal transduction. First, I’ll briefly summarize the mechanical, biochemical and physicochemical material properties that influence cellular sensing and subsequent integration with the tissues at the macroscale. Controlling signal transduction at the submicron scale, however, requires careful materials engineering to address the need for minimally invasive targeting of single proteins and for providing sufficient physical stimuli for cellular signaling. I will discuss an approach to fabricate anisotropic magnetite nanodiscs (MNDs) which can be used as torque transducers to mechanosensory cells under weak, slowly varying magnetic fields (MFs). When MNDs are coupled to MFs, their magnetization transitions between a vortex and in-plane state, leading to torques on the pN scale, sufficient to activate mechanosensitive ion channels in neuronal cell membranes. This approach opens new avenues for studies of biological mechanoreception and provides new tools for minimally invasive neuromodulation technology.

  • Daniel Razansky
  • MPI-IS Stuttgart, Heisenbergstr. 3, room 2R4

Optoacoustic imaging is increasingly attracting the attention of the biomedical research community due to its excellent spatial and temporal resolution, centimeter scale penetration into living tissues, versatile endogenous and exogenous optical absorption contrast. State-of-the-art implementations of multi-spectral optoacoustic tomography (MSOT) are based on multi-wavelength excitation of tissues to visualize specific molecules within opaque tissues. As a result, the technology can noninvasively deliver structural, functional, metabolic, and molecular information from living tissues. The talk covers most recent advances pertaining ultrafast imaging instrumentation, multi-modal combinations with optical and ultrasound methods, intelligent reconstruction algorithms as well as smart optoacoustic contrast and sensing approaches. Our current efforts are also geared toward exploring potential of the technique in studying multi-scale dynamics of the brain and heart, monitoring of therapies, fast tracking of cells and targeted molecular imaging applications. MSOT further allows for a handheld operation thus offers new level of precision for clinical diagnostics of patients in a number of indications, such as breast and skin lesions, inflammatory diseases and cardiovascular diagnostics.

Organizers: Metin Sitti

  • Prof. CheolGi KIm
  • 3P02

The precise delivery of bio-functionalized matters is of great interest from the fundamental and applied viewpoints. Particularly, most existing single cell platforms are unable to achieve large scale operation with flexibility on cells and digital manipulation towards multiplex cell tweezers. Thus, there is an urgent need of innovative techniques to accomplish the automation of single cells. Recently, the flexibility of magnetic shuttling technology using nano/micro scale magnets for the manipulation of particles has gained significant advances and has been used for a wide variety of single cells manipulation tasks. Herein, let’s call “spintrophoresis” using micro-/nano-sized Spintronic devices rather than “magnetophoresis” using bulk magnet. Although a digital manipulation of single cells has been implemented by the integrated circuits of spintrophoretic patterns with current, active and passive sorting gates are required for its practical application for cell analysis. Firstly, a universal micromagnet junction for passive self-navigating gates of microrobotic carriers to deliver the cells to specific sites using a remote magnetic field is described for passive cell sorting. In the proposed concept, the nonmagnetic gap between the defined donor and acceptor micromagnets creates a crucial energy barrier to restrict particle gating. It is shown that by carefully designing the geometry of the junctions, it becomes possible to deliver multiple protein- functionalized carriers in high resolution, as well as MFC-7 and THP-1 cells from the mixture, with high fidelity and trap them in individual apartments. Secondly, a convenient approach using multifarious transit gates is proposed for active sorting of specific cells that can pass through the local energy barriers by a time-dependent pulsed magnetic field instead of multiple current wires. The multifarious transit gates including return, delay, and resistance linear gates, as well as dividing, reversed, and rectifying T-junction gates, are investigated theoretically and experimentally for the programmable manipulation of microrobotic particles. The results demonstrate that, a suitable angle of the 3D-gating field at a suitable time zone is crucial to implement digital operations at integrated multifarious transit gates along bifurcation paths to trap microrobotic carriers in specific apartments, paving the way for flexible on-chip arrays of multiplexed cells. Finally, I will include the pseudo-diamagnetic spintrophoresis using negative magnetic patterns for multiplexed magnetic tweezers without the biomarker labelling. Label free single cells manipulation, separation and localization enables a novel platform to address biologically relevant problems in bio-MEMS/ NEMS technologies.

Kirigami-Inspired Metamaterials - from Morphable Structures to Soft Robots

IS Colloquium
  • 09 January 2020 • 16:00—17:00
  • Katia Bertoldi
  • Room 2P04 in Stuttgart and broadcast to room N0.002 in Tübingen

In the search for materials with new properties, there have been great advances in recent years aimed at the construction of mechanical systems whose behaviour is governed by structure, rather than composition. Through careful design of the material’s architecture, new material properties have been demonstrated, including negative Poisson’s ratio, high stiffness-to-weight ratio and mechanical cloaking. While originally the field focused on achieving unusual (zero or negative) values for familiar mechanical parameters, more recently it has been shown that non-linearities can be exploited to further extend the design space. In this talk Prof. Katia Bertoldi will focus on kirigami-inspired metamaterials, which are produced by introducing arrays of cuts into thin sheets. First, she will demonstrate that instabilities triggered under uniaxial tension can be exploited to create complex 3D patterns and even to guide the formation of permanent folds. Second, she will show that such non-linear systems can be used to designs smart and flexible skins with anisotropic frictional properties that enables a single soft actuator to propel itself. Finally, Prof.Bertoldi will focus on bistable kirigami metamaterials and show that they provide an ideal environment for the propagation non-linear waves.

Organizers: Metin Sitti

  • Ye Zhao
  • MPI-IS Stuttgart, Heisenbergstr. 3, room 2P04

The demand for safe, robust, and intelligent robotic systems is growing rapidly, given their potential to make our societies more productive and increase our welfare. To achieve this, robots are increasingly expected to operate in human-populated environments, maneuver in remote and cluttered environments, maintain and repair facilities, take care of our health, and streamline manufacturing and assembly lines. However, computational issues limit the ability of robots to plan complex motions in constrained and contact-rich environments, interact with humans safely, and exploit dynamics to gracefully maneuver, manipulate, fly, or explore the oceans. This talk will be centered around planning and decision-making algorithms for robust and agile robots operating in complex environments. In particular, Dr. Zhao will present novel computational approaches necessary to enable real-time and robust motion planning of highly dynamic bipedal locomotion over rough terrain. This planning approach revolves around robust disturbance metrics, an optimal recovery controller, and foot placement re-planning strategies. Extending this motion planning approach to generalized whole-body locomotion behaviors, He will introduce our recent progress on high-level reactive task planner synthesis for multi-contact, template-based locomotion interacting with constrained environments and how to integrate formal methods for mission-capable locomotion. This talk will also present robust trajectory optimization algorithm capable of handling contact uncertainties and without enumerating contact modes. Dr. Zhao will end this talk with current research directions on distributed trajectory optimization and task and motion planning.

Organizers: Metin Sitti

  • Majid Taghavi
  • MPI-IS Stuttgart, Room 2P4, Heisenbergstraße 3

In this talk, Majid Taghavi will briefly discuss the demand for high-performance electromechanical transducers, the current challenges, and approaches he has been pursuing to tackle them. He will discuss multiple electromechanical concepts and devices that he has delivered for low-power energy harvesting, self-powered sensors, and artificial muscle technologies. Majid Taghavi will look into piezoelectric, triboelectric, electrostatic, dielectrophoretic, and androphilic phenomena, and will show his observations and innovations in coupling physical phenomena and developing smart materials and intelligent devices.

Organizers: Metin Sitti

  • Eric R. Dufresne
  • MPI-IS Stuttgart, Room 2P4, Heisenbergstraße 3

Prof. Eric Dufresne will describe some experiments on some simple composites of elastomers and droplets. First, we will consider their composite mechanical properties. He will show how simple liquid droplets can counterintuitively stiffen the material, and how magnetorheological fluid droplets can provide elastomers with magnetically switchable shape memory. Second, we consider the nucleation, growth, and ripening of droplets within an elastomer. Here, a variety of interesting phenomena emerge: size-tunable monodisperse droplets, shape-tunable droplets, and ripening of droplets along stiffness gradients. We are exploiting these phenomena to make materials with mechanically switchable structural color.

Organizers: Metin Sitti

  • Prof. Pietro Valdastri and Prof. Russel Harris
  • Room 2P4, Heisenbergstraße 3, 70569 Stuttgart

Prof. Pietro Valdastri's talk will focus on Medical Capsule Robots. Capsule robots are cm-size devices that leverage extreme miniaturization to access and operate in environments that are out of reach for larger robots. In medicine, capsule robots can be designed to be swallowed like a pill and to diagnose and treat mortal diseases, such as cancer. The talk will move from capsule robots for the inspection of the digestive tract toward a new generation of surgical robots and devices, having a relevant reduction in size, invasiveness, and cost as the main drivers for innovation. During the talk, we will discuss the recent enabling technologies that are being developed at the University of Leeds to transform medical robotics. These technologies include magnetic manipulation of capsule robots, hydraulic and pneumatic actuation, real-time tracking of capsule position and orientation, ultra-low-cost design, frugal innovation, and autonomy in robotic endoscopy.
Prof. Russell Harris has been researching new manufacturing processes for over 20 years. He has several research projects focussing on robotics, and is particularly interested in how new manufacturing processes can be an enabler to advanced robotic devices and components. In this talk he will discuss some of this research and where he believes there may be new opportunities for collaborative research across manufacturing and robotics.