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  - 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  -