@article{FangGouldLysyakovaetal.2018,
  author    = {Fang, Liang and Gould, Oliver E. C. and Lysyakova, Liudmila and Jiang, Yi and Sauter, Tilman and Frank, Oliver and Becker, Tino and Schossig, Michael and Kratz, Karl and Lendlein, Andreas},
  title     = {Implementing and quantifying the shape-memory effect of single polymeric micro/nanowires with an atomic force microscope},
  series = {ChemPhysChem : a European journal of chemical physics and physical chemistry},
  volume    = {19},
  journal   = {ChemPhysChem : a European journal of chemical physics and physical chemistry},
  number    = {16},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {1439-4235},
  doi       = {10.1002/cphc.201701362},
  pages     = {2078 -- 2084},
  year      = {2018},
  abstract  = {The implementation of shape-memory effects (SME) in polymeric micro- or nano-objects currently relies on the application of indirect macroscopic manipulation techniques, for example, stretchable molds or phantoms, to ensembles of small objects. Here, we introduce a method capable of the controlled manipulation and SME quantification of individual micro- and nano-objects in analogy to macroscopic thermomechanical test procedures. An atomic force microscope was utilized to address individual electro-spun poly(ether urethane) (PEU) micro- or nanowires freely suspended between two micropillars on a micro-structured silicon substrate. In this way, programming strains of 10 +/- 1\% or 21 +/- 1\% were realized, which could be successfully fixed. An almost complete restoration of the original free-suspended shape during heating confirmed the excellent shape-memory performance of the PEU wires. Apparent recovery stresses of sigma(max,app)=1.2 +/- 0.1 and 33.3 +/- 0.1MPa were obtained for a single microwire and nanowire, respectively. The universal AFM test platform described here enables the implementation and quantification of a thermomechanically induced function for individual polymeric micro- and nanosystems.},
  language  = {en}
}
@article{WangRazzaqRudolphetal.2018,
  author    = {Wang, Li and Razzaq, Muhammad Yasar and Rudolph, Tobias and Heuchel, Matthias and N{\"o}chel, Ulrich and Mansfeld, Ulrich and Jiang, Yi and Gould, Oliver E. C. and Behl, Marc and Kratz, Karl and Lendlein, Andreas},
  title     = {Reprogrammable, magnetically controlled polymeric nanocomposite actuators},
  series = {Material horizons},
  volume    = {5},
  journal   = {Material horizons},
  number    = {5},
  publisher = {Royal Society of Chemistry},
  address   = {Cambridge},
  issn      = {2051-6347},
  doi       = {10.1039/c8mh00266e},
  pages     = {861 -- 867},
  year      = {2018},
  abstract  = {Soft robots and devices with the advanced capability to perform adaptive motions similar to that of human beings often have stimuli-sensitive polymeric materials as the key actuating component. The external signals triggering the smart polymers' actuations can be transmitted either via a direct physical connection between actuator and controlling unit (tethered) or remotely without a connecting wire. However, the vast majority of such polymeric actuator materials are limited to one specific type of motion as their geometrical information is chemically fixed. Here, we present magnetically driven nanocomposite actuators, which can be reversibly reprogrammed to different actuation geometries by a solely physical procedure. Our approach is based on nanocomposite materials comprising spatially segregated crystallizable actuation and geometry determining units. Upon exposure to a specific magnetic field strength the actuators' geometric memory is erased by the melting of the geometry determining units allowing the implementation of a new actuator shape. The actuation performance of the nanocomposites can be tuned and the technical significance was demonstrated in a multi-cyclic experiment with several hundreds of repetitive free-standing shape shifts without losing performance.},
  language  = {en}
}
@article{JiangMansfeldFangetal.2018,
  author    = {Jiang, Yi and Mansfeld, Ulrich and Fang, Liang and Kratz, Karl and Lendlein, Andreas},
  title     = {Temperature-induced evolution of microstructures on poly[ethylene-co-(vinyl acetate)] substrates switches their underwater wettability},
  series = {Materials \& design},
  volume    = {163},
  journal   = {Materials \& design},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0264-1275},
  doi       = {10.1016/j.matdes.2018.12.002},
  pages     = {10},
  year      = {2018},
  abstract  = {Material surfaces with tailored aerophobicity are crucial for applications where gas bubble wettability has to be controlled, e.g., gas storage and transport, electrodes, bioreactors or medical devices. Here, we present switchable underwater aerophobicity of hydrophobic polymeric substrates, which respond to heat with multilevel micro-and nanotopographical changes. The cross-linked poly[ethylene-co-(vinyl acetate)] substrates possess arrays of microcylinders with a nanorough top surface. It is hypothesized that the specific micro-/nanotopography of the surface allows trapping of a water film at the micro interspace and in this way generates the aerophobic behavior. The structured substrates were programmed to a temporarily stable, nanoscale flat substrate showing aerophilic behavior. Upon heating, the topographical changes caused a switch in contact angle from aerophilic to aerophobic for approaching air bubbles. In this way, the initial adhesion of air bubbles to the programmed flat substrate could be turned into repellence for the recovered substrate surface. The temperature at which the repellence of air bubbles starts can be adjusted from 58 +/- 3 degrees C to 73 +/- 3 degrees C by varying the deformation temperature applied during the temperature-memory programming procedure. The presented actively switching polymeric substrates are attractive candidates for applications, where an on-demand gas bubble repellence is advantageous. (c) 2018 Helmholtz-Zentrum Geesthacht, Zentrum fur Material- und Kustenforschung. Published by Elsevier Ltd.},
  language  = {en}
}
@article{JiangMansfeldKratzetal.2019,
  author    = {Jiang, Yi and Mansfeld, Ulrich and Kratz, Karl and Lendlein, Andreas},
  title     = {Programmable microscale stiffness pattern of flat polymeric substrates by temperature-memo technology},
  series = {MRS Communications},
  volume    = {9},
  journal   = {MRS Communications},
  number    = {1},
  publisher = {Cambridge Univ. Press},
  address   = {New York},
  issn      = {2159-6859},
  doi       = {10.1557/mrc.2019.24},
  pages     = {181 -- 188},
  year      = {2019},
  abstract  = {Temperature-memory technology was utilized to generate flat substrates with a programmable stiffness pattern from cross-linked poly(ethylene-co-vinyl acetate) substrates with cylindrical microstructures. Programmed substrates were obtained by vertical compression at temperatures in the range from 60 to 100 degrees C and subsequent cooling, whereby a flat substrate was achieved by compression at 72 degrees C, as documented by scanning electron microscopy and atomic force microscopy (AFM). AFM nanoindentation experiments revealed that all programmed substrates exhibited the targeted stiffness pattern. The presented technology for generating polymeric substrates with programmable stiffness pattern should be attractive for applications such as touchpads. optical storage, or cell instructive substrates.},
  language  = {en}
}
@misc{JiangMansfeldKratzetal.2019,
  author    = {Jiang, Yi and Mansfeld, Ulrich and Kratz, Karl and Lendlein, Andreas},
  title     = {Programmable microscale stiffness pattern of flat polymeric substrates by temperature-memory technology},
  series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  volume    = {9},
  journal   = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  number    = {1},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-46974},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-469745},
  pages     = {181 -- 188},
  year      = {2019},
  abstract  = {Temperature-memory technology was utilized to generate flat substrates with a programmable stiffness pattern from cross-linked poly(ethylene-co-vinyl acetate) substrates with cylindrical microstructures. Programmed substrates were obtained by vertical compression at temperatures in the range from 60 to 100 degrees C and subsequent cooling, whereby a flat substrate was achieved by compression at 72 degrees C, as documented by scanning electron microscopy and atomic force microscopy (AFM). AFM nanoindentation experiments revealed that all programmed substrates exhibited the targeted stiffness pattern. The presented technology for generating polymeric substrates with programmable stiffness pattern should be attractive for applications such as touchpads. optical storage, or cell instructive substrates.},
  language  = {en}
}
@article{BlockiLoewenbergJiangetal.2017,
  author    = {Blocki, Anna and L{\"o}wenberg, Candy and Jiang, Yi and Kratz, Karl and Neffe, Axel T. and Jung, Friedrich and Lendlein, Andreas},
  title     = {Response of encapsulated cells to a gelatin matrix with varied bulk and microenvironmental elastic properties},
  series = {Polymers for advanced technologies},
  volume    = {28},
  journal   = {Polymers for advanced technologies},
  publisher = {Wiley},
  address   = {Hoboken},
  issn      = {1042-7147},
  doi       = {10.1002/pat.3947},
  pages     = {1245 -- 1251},
  year      = {2017},
  abstract  = {Gelatin-based hydrogels offer various biochemical cues that support encapsulated cells and are therefore suitable as cell delivery vehicles in regenerative medicine. However, besides the biochemical signals, biomechanical cues are crucial to ensure an optimal support of encapsulated cells. Hence, we aimed to correlate the cellular response of encapsulated cells to macroscopic and microscopic elastic properties of glycidylmethacrylate (GMA)-functionalized gelatin-based hydrogels. To ensure that different observations in cellular behavior could be attributed to differences in elastic properties, an identical concentration as well as degree of functionalization of biopolymers was utilized to form covalently crosslinked hydrogels. Elastic properties were merely altered by varying the average gelatin-chain length. Hydrogels exhibited an increased degree of swelling and a decreased bulk elastic modulus G with prolonged autoclaving of the starting solution. This was accompanied by an increase of hydrogel mesh size and thus by a reduction of crosslinking density. Tougher hydrogels retained the largest amount of cells; however, they also interfered with cell viability. Softer gels contained a lower cell density, but supported cell elongation and viability. Observed differences could be partially attributed to differences in bulk properties, as high crosslinking densities interfere with diffusion and cell spreading and thus can impede cell viability. Interestingly, a microscopic elastic modulus in the range of native soft tissue supported cell viability and elongation best while ensuring a good cell entrapment. In conclusion, gelatin-based hydrogels providing a soft tissue-like microenvironment represent adequate cell delivery vehicles for tissue engineering approaches. Copyright (c) 2016 John Wiley \& Sons, Ltd.},
  language  = {en}
}
@phdthesis{Jiang2019,
  author    = {Jiang, Yi},
  title     = {Tailoring surface functions of micro/nanostructured polymeric substrates by thermo-mechanical treatments},
  school      = {Universit{\"a}t Potsdam},
  pages     = {93},
  year      = {2019},
  language  = {en}
}
@misc{JiangMansfeldFangetal.2018,
  author    = {Jiang, Yi and Mansfeld, Ulrich and Fang, Liang and Kratz, Karl and Lendlein, Andreas},
  title     = {Temperature-induced evolution of microstructures on poly[ethylene-co-(vinyl acetate)] substrates switches their underwater wettability},
  series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  number    = {639},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-42460},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-424601},
  pages     = {10},
  year      = {2018},
  abstract  = {Material surfaces with tailored aerophobicity are crucial for applications where gas bubble wettability has to be controlled, e.g., gas storage and transport, electrodes, bioreactors or medical devices. Here, we present switchable underwater aerophobicity of hydrophobic polymeric substrates, which respond to heat with multilevel micro- and nanotopographical changes. The cross-linked poly[ethylene-co-(vinyl acetate)] substrates possess arrays of microcylinders with a nanorough top surface. It is hypothesized that the specific micro-/nanotopography of the surface allows trapping of a water film at the micro interspace and in this way generates the aerophobic behavior. The structured substrates were programmed to a temporarily stable, nanoscale flat substrate showing aerophilic behavior. Upon heating, the topographical changes caused a switch in contact angle from aerophilic to aerophobic for approaching air bubbles. In this way, the initial adhesion of air bubbles to the programmed flat substrate could be turned into repellence for the recovered substrate surface. The temperature at which the repellence of air bubbles starts can be adjusted from 58 ± 3 °C to 73 ± 3 °C by varying the deformation temperature applied during the temperature-memory programming procedure. The presented actively switching polymeric substrates are attractive candidates for applications, where an on-demand gas bubble repellence is advantageous.},
  language  = {en}
}