TY  - JOUR
A1  - Xu, QingHai
A1  - Cao, Xianyong
A1  - Tian, Fang
A1  - Zhang, ShengRui
A1  - Li, YueCong
A1  - Li, ManYue
A1  - Li, Jie
A1  - Liu, YaoLiang
A1  - Liang, Jian
T1  - Relative pollen productivities of typical steppe species in northern China and their potential in past vegetation reconstruction
JF  - Science China
N2  - The Relative Pollen Productivities (RPPs) of common steppe species are estimated using Extended R-value (ERV) model based on pollen analysis and vegetation survey of 30 surface soil samples from typical steppe area of northern China. Artemisia, Chenopodiaceae, Poaceae, Cyperaceae, and Asteraceae are the dominant pollen types in pollen assemblages, reflecting the typical steppe communities well. The five dominant pollen types and six common types (Thalictrum, Iridaceae, Potentilla, Ephedra, Brassicaceae, and Ulmus) have strong wind transport abilities; the estimated Relevant Source Area of Pollen (RSAP) is ca. 1000 m when the sediment basin radius is set at 0.5 m. Ulmus, Artemisia, Brassicaceae, Chenopodiaceae, and Thalictrum have relative high RPPs; Poaceae, Cyperaceae, Potentilla, and Ephedra pollen have moderate RPPs; Asteraceae and Iridaceae have low RPPs. The reliability test of RPPs revealed that most of the RPPs are reliable in past vegetation reconstruction. However, the RPPs of Asteraceae and Iridaceae are obviously underestimated, and those of Poaceae, Chenopodiaceae, and Ephedra are either slightly underestimated or slightly overestimated, suggesting that those RPPs should be considered with caution. These RPPs were applied to estimating plant abundances for two fossil pollen spectra (from the Lake Bayanchagan and Lake Haoluku) covering the Holocene in typical steppe area, using the "Regional Estimates of Vegetation Abundance from Large Sites" (REVEALS) model. The RPPs-based vegetation reconstruction revealed that meadow-steppe dominated by Poaceae, Cyperaceae, and Artemisia plants flourished in this area before 6500-5600 cal yr BP, and then was replaced by present typical steppe.
KW  - typical steppe
KW  - modern surface pollen
KW  - relative pollen productivity
KW  - relevant pollen source area
KW  - paleovegetation
Y1  - 2014
U6  - https://doi.org/10.1007/s11430-013-4738-7
SN  - 1674-7313
SN  - 1869-1897
VL  - 57
IS  - 6
SP  - 1254
EP  - 1266
PB  - Science China Press
CY  - Beijing
ER  - 
TY  - JOUR
A1  - Jiang, Yi
A1  - Mansfeld, Ulrich
A1  - Fang, Liang
A1  - Kratz, Karl
A1  - Lendlein, Andreas
T1  - Temperature-induced evolution of microstructures on poly[ethylene-co-(vinyl acetate)] substrates switches their underwater wettability
JF  - Materials & design
N2  - 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.
KW  - Aerophobicity
KW  - Temperature-memory effect
KW  - Switchable wettability
KW  - Air bubble repellence
KW  - Thermo-responsive polymer
Y1  - 2018
U6  - https://doi.org/10.1016/j.matdes.2018.12.002
SN  - 0264-1275
SN  - 1873-4197
VL  - 163
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Yan, Wan
A1  - Fang, Liang
A1  - Weigel, Thomas
A1  - Behl, Marc
A1  - Kratz, Karl
A1  - Lendlein, Andreas
T1  - The influence of thermal treatment on the morphology in differently prepared films of a oligodepsipeptide based multiblock copolymer
JF  - Polymers for advanced technologies
N2  - Degradable multiblock copolymers prepared from equal weight amounts of poly(epsilon-caprolactone)-diol (PCL-diol) and poly[oligo(3S-iso-butylmorpholine-2,5-dione)]-diol (PIBMD-diol), named PCL-PIBMD, provide a phase-segregated morphology. It exhibits a low melting temperature from PCL domains (T-m,T-PCL) of 382 degrees C and a high T-m,T-PIBMD of 170 +/- 2 degrees C with a glass transition temperature (T-g,T-PIBMD) at 42 +/- 2 degrees C from PIBMD domains. In this study, we explored the influence of applying different thermal treatments on the resulting morphologies of solution-cast and spin-coated PCL-PIBMD thin films, which showed different initial surface morphologies. Differential scanning calorimetry results and atomic force microscopy images after different thermal treatments indicated that PCL and PIBMD domains showed similar crystallization behaviors in 270 +/- 30 mu m thick solution-cast films as well as in 30 +/- 2 and 8 +/- 1nm thick spin-coated PCL-PIBMD films. Existing PIBMD crystalline domains highly restricted the generation of PCL crystalline domains during cooling when the sample was annealed at 180 degrees C. By annealing the sample above 120 degrees C, the PIBMD domains crystallized sufficiently and covered the free surface, which restricted the crystallization of PCL domains during cooling. The PCL domains can crystallize by hindering the crystallization of PIBMD domains via the fast vitrification of PIBMD domains when the sample was cooled/quenched in liquid nitrogen after annealing at 180 degrees C. These findings contribute to a better fundamental understanding of the crystallization mechanism of multi-block copolymers containing two crystallizable domains whereby the T-g of the higher melting domain type is in the same temperature range as the T-m of the lower melting domain type. Copyright (c) 2016 John Wiley & Sons, Ltd.
KW  - multiblock copolymer
KW  - oligodepsipeptides
KW  - phase morphology
KW  - thermal treatments
KW  - crystallization behavior
Y1  - 2017
U6  - https://doi.org/10.1002/pat.3953
SN  - 1042-7147
SN  - 1099-1581
VL  - 28
SP  - 1339
EP  - 1345
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Yan, Wan
A1  - Fang, Liang
A1  - Nöchel, Ulrich
A1  - Gould, Oliver E. C.
A1  - Behl, Marc
A1  - Kratz, Karl
A1  - Lendlein, Andreas
T1  - Investigating the roles of crystallizable and glassy switching segments within multiblock copolymer shape-memory materials
JF  - MRS Advances
N2  - The variation of the molecular architecture of multiblock copolymers has enabled the introduction of functional behaviour and the control of key mechanical properties. In the current study, we explore the synergistic relationship of two structural components in a shape-memory material formed of a multiblock copolymer with crystallizable poly(epsilon-caprolactone) and crystallizable polyfoligo(3S-iso-butylmorpholine-2,5-dione) segments (PCL-PIBMD). The thermal and structural properties of PCL-PIBMD films were compared with PCI.-PU and PMMD-PU investigated by means of DSC, SAXS and WARS measurements. The shape-memory properties were quantified by cyclic, thermomechanical tensile tests, where deformation strains up to 900% were applied for programming PCL-PIBMD films at 50 degrees C. Toluene vapor treatment experiments demonstrated that the temporary shape was fixed mainly by glassy PIBMD domains at strains lower than 600% with the PCL contribution to fixation increasing to 42 +/- 2% at programming strains of 900% This study into the shape-memory mechanism of PCL-PIBMD provides insight into the structure function relation in multiblock copolymers with both crystallizable and glassy switching segments.
Y1  - 2018
U6  - https://doi.org/10.1557/adv.2018.590
SN  - 2059-8521
VL  - 3
IS  - 63
SP  - 3741
EP  - 3749
PB  - Cambridge Univ. Press
CY  - New York
ER  - 
TY  - JOUR
A1  - Wang, Li
A1  - Heuchel, Matthias
A1  - Fang, Liang
A1  - Kratz, Karl
A1  - Lendlein, Andreas
T1  - Influence of a polyester coating of magnetic nanoparticles on magnetic heating behavior of shape-memory polymer-based composites
JF  - Journal of applied biomaterials & functional materials
N2  - Background: Magnetic composites of thermosensitive shape-memory polymers (SMPs) and magnetite nanoparticles (MNPs) allow noncontact actuation of the shape-memory effect in an alternating magnetic field. In this study, we investigated whether the magnetic heating capability of cross-linked poly(epsilon-caprolactone)/MNP composites (cPCLC) could be improved by covalent coating of MNPs with oligo(epsilon-caprolactone) (OCL).
 Methods: Two different types of cPCLC containing uncoated and OCL-coated MNP with identical magnetite weight content were prepared by thermally induced polymerization of poly(epsilon-caprolactone) diisocyanatoethyl methacrylate. Both cPCLCs exhibited a melting transition at T-m = 48 degrees C, which could be used as switching transition.
 Results: The dispersion of the embedded nanoparticles within the polymer matrix could be substantially improved, when the OCL-coated MNPs were used, as visualized by scanning electron microscopy. We could further demonstrate that in this way the maximal achievable bulk temperature (T-bulk) obtained within the cPCLC test specimen in magnetic heating experiments at a magnetic field strength of H = 30 kA.m(-1) could be increased from T bulk = 48 degrees C to T bulk = 74 degrees C.
KW  - Magnetic composites
KW  - Magnetite nanoparticles
KW  - Polymer networks
KW  - Shape-memory effect
Y1  - 2012
U6  - https://doi.org/10.5301/JABFM.2012.10293
SN  - 2280-8000
VL  - 10
IS  - 3
SP  - 203
EP  - 209
PB  - Wichtig
CY  - Milano
ER  - 
TY  - JOUR
A1  - Zhang, Quanchao
A1  - Sauter, Tilman
A1  - Fang, Liang
A1  - Kratz, Karl
A1  - Lendlein, Andreas
T1  - Shape-Memory Capability of Copolyetheresterurethane Microparticles Prepared via Electrospraying
JF  - Macromolecular materials and engineering
N2  - Multifunctional thermo-responsive and degradable microparticles exhibiting a shapememory effect (SME) have attracted widespread interest in biomedicine as switchable delivery vehicles or microactuators. In this work almost spherical solid microparticles with an average diameter of 3.9 +/- 0.9 mm are prepared via electrospraying of a copolyetheresterurethane named PDC, which is composed of crystallizable oligo(p-dioxanone) (OPDO) hard and oligo(e-caprolactone) (OCL) switching segments. The PDC microparticles are programmed via compression at different pressures and their shapememory capability is explored by off-line and online heating experiments. When a low programming pressure of 0.2 MPa is applied a pronounced thermally-induced shape-memory effect is achieved with a shape recovery ratio about 80%, while a high programming pressure of 100 MPa resulted in a weak shape-memory performance. Finally, it is demonstrated that an array of PDC microparticles deposited on a polypropylene (PP) substrate can be successfully programmed into a smart temporary film, which disintegrates upon heating to 60 degrees C.
KW  - biomaterials
KW  - microparticles
KW  - processing
KW  - stimuli-sensitive polymers
KW  - shape-memory effect
Y1  - 2015
U6  - https://doi.org/10.1002/mame.201400267
SN  - 1438-7492
SN  - 1439-2054
VL  - 300
IS  - 5
SP  - 522
EP  - 530
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Fang, Liang
A1  - Gould, Oliver E. C.
A1  - Lysyakova, Liudmila
A1  - Jiang, Yi
A1  - Sauter, Tilman
A1  - Frank, Oliver
A1  - Becker, Tino
A1  - Schossig, Michael
A1  - Kratz, Karl
A1  - Lendlein, Andreas
T1  - Implementing and quantifying the shape-memory effect of single polymeric micro/nanowires with an atomic force microscope
JF  - ChemPhysChem : a European journal of chemical physics and physical chemistry
N2  - 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.
KW  - cyclic thermomechanical testing
KW  - atomic force microscopy
KW  - soft matter micro- and nanowires
KW  - shape-memory effect
KW  - materials science
Y1  - 2018
U6  - https://doi.org/10.1002/cphc.201701362
SN  - 1439-4235
SN  - 1439-7641
VL  - 19
IS  - 16
SP  - 2078
EP  - 2084
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Krüger-Genge, Anne
A1  - Dietze, Stefanie
A1  - Yan, Wan
A1  - Liu, Yue
A1  - Fang, Liang
A1  - Kratz, Karl
A1  - Lendlein, Andreas
A1  - Jung, Friedrich
T1  - Endothelial cell migration, adhesion and proliferation on different polymeric substrates
JF  - Clinical hemorheology and microcirculation : blood flow and vessels
N2  - BACKGROUND: The formation of a functionally-confluent endothelial cell (EC) monolayer affords proliferation of EC, which only happens in case of appropriate migratory activity. AIM OF THE STUDY: The migratory pathway of human umbilical endothelial cells (HUVEC) was investigated on different polymeric substrates. MATERIAL AND METHODS: Surface characterization of the polymers was performed by contact angle measurements and atomic force microscopy under wet conditions. 30,000 HUVEC per well were seeded on polytetrafluoroethylene (PTFE) (theta(adv) = 119 degrees +/- 2 degrees), on low-attachment plate LAP (theta(adv) = 28 degrees +/- 2 degrees) and on polystyrene based tissue culture plates (TCP, theta(adv) = 22 degrees +/- 1 degrees). HUVEC tracks (trajectories) were recorded by time lapse microscopy and the euclidean distance (straight line between starting and end point), the total distance and the velocities of HUVEC not leaving the vision field were determined. RESULTS: On PTFE, 42 HUVEC were in the vision field directly after seeding. The mean length of single migration steps (SML) was 6.1 +/- 5.2 mu m, the mean velocity (MV) 0.40 +/- 0.3 mu m.min(-1) and the complete length of the trajectory (LT) was 710 +/- 440 mu m. On TCP 82 HUVEC were in the vision field subsequent to seeding. The LT was 840 +/- 550 mu m, the SML 6.1 +/- 5.2 mu m and the MV 0.44 +/- 0.3 mu m.min(-1). The trajectories on LAP differed significantly in respect to SML (2.4 +/- 3.9 mu m, p <0.05), the MV (0.16 +/- 0.3 mu m.min(-1), p <0.05) and the LT (410 +/- 300 mu m, p <0.05), compared to PTFE and TCP. Solely on TCP a nearly confluent EC monolayer developed after three days. While on TCP diffuse signals of vinculin were found over the whole basal cell surface organizing the binding of the cells by focal adhesions, on PTFE vinculin was merely arranged at the cell rims, and on the hydrophilic material (LAP) no focal adhesions were found. CONCLUSION: The study revealed that the wettability of polymers affected not only the initial adherence but also the migration of EC, which is of importance for the proliferation and ultimately the endothelialization of polymer-based biomaterials.
KW  - Endothelial cells
KW  - migration
KW  - polymer-based biomaterials
KW  - cytokine release
Y1  - 2019
U6  - https://doi.org/10.3233/CH-189317
SN  - 1386-0291
SN  - 1875-8622
VL  - 70
IS  - 4
SP  - 511
EP  - 529
PB  - IOS Press
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Liu, Yue
A1  - Razzaq, Muhammad Yasar
A1  - Rudolph, Tobias
A1  - Fang, Liang
A1  - Kratz, Karl
A1  - Lendlein, Andreas
T1  - Two-Level Shape Changes of Polymeric Microcuboids Prepared from Crystallizable Copolymer Networks
JF  - Macromolecules : a publication of the American Chemical Society
N2  - Polymeric microdevices bearing features like nonspherical shapes or spatially segregated surface properties are of increasing importance in biological and medical analysis, drug delivery, and bioimaging or microfluidic systems as well as in micromechanics, sensors, information storage, or data carrier devices. Here, a method to fabricate programmable microcuboids with shape-memory capability and the quantification of their recovery at different levels is reported. The method uses the soft lithographic technique to create microcuboids with well-defined sizes and surface properties. Microcuboids having an edge length of 25 mu m and a height of 10 mu m were prepared from cross-linked poly[ethylene-co-(vinyl acetate)] (cPEVA) with different vinyl acetate contents and were programmed by compression with various deformation degrees at elevated temperatures. The microlevel shape-recovery of the cuboidal geometry during heating was monitored by optical microscopy (OM) and atomic force microscopy (AFM) studying the related changes in the projected area (PA) or height, while the nanolevel changes of the nanosurface roughness were investigated by in situ AFM. The shape-memory effect at the microlevel was quantified by the recovery ratio of cuboids (R-r,R-micro), while at the. nanolevel, the recovery ratio of the nanoroughness (R-r,R-nano) was measured. The values of R-r,R-micro,,micro could be tailored in a range from 42 +/- 1% to 102 +/- 1% and Rr,nano from 89 +/- 6% to 136 +/- 21% depending on the applied compression ratio and the amount of vinyl acetate content in the cPEVA microcuboids.
Y1  - 2017
U6  - https://doi.org/10.1021/acs.macromol.6b02237
SN  - 0024-9297
SN  - 1520-5835
VL  - 50
SP  - 2518
EP  - 2527
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Liu, Yue
A1  - Gould, Oliver E. C.
A1  - Rudolph, Tobias
A1  - Fang, Liang
A1  - Kratz, Karl
A1  - Lendlein, Andreas
T1  - Polymeric microcuboids programmable for temperature-memory
JF  - Macromolecular materials and engineering
N2  - Microobjects with programmable mechanical functionality are highly desirable for the creation of flexible electronics, sensors, and microfluidic systems, where fabrication/programming and quantification methods are required to fully control and implement dynamic physical behavior. Here, programmable microcuboids with defined geometries are prepared by a template-based method from crosslinked poly[ethylene-co-(vinyl acetate)] elastomers. These microobjects could be programmed to exhibit a temperature-memory effect or a shape-memory polymer actuation capability. Switching temperaturesT(sw)during shape recovery of 55 +/- 2, 68 +/- 2, 80 +/- 2, and 86 +/- 2 degrees C are achieved by tuning programming temperatures to 55, 70, 85, and 100 degrees C, respectively. Actuation is achieved with a reversible strain of 2.9 +/- 0.2% to 6.7 +/- 0.1%, whereby greater compression ratios and higher separation temperatures induce a more pronounced actuation. Micro-geometry change is quantified using optical microscopy and atomic force microscopy. The realization and quantification of microparticles, capable of a tunable temperature responsive shape-change or reversible actuation, represent a key development in the creation of soft microscale devices for drug delivery or microrobotics.
KW  - actuation
KW  - atomic force microscopy
KW  - biomaterials
KW  - microparticles
KW  - shape-memory polymers
Y1  - 2020
U6  - https://doi.org/10.1002/mame.202000333
SN  - 1438-7492
SN  - 1439-2054
VL  - 305
IS  - 10
PB  - Wiley-VCH
CY  - Weinheim
ER  -