@article{BalkBehlNoecheletal.2021,
  author    = {Balk, Maria and Behl, Marc and N{\"o}chel, Ulrich and Lendlein, Andreas},
  title     = {Enzymatically triggered Jack-in-the-box-like hydrogels},
  series = {ACS applied materials \& interfaces / American Chemical Society},
  volume    = {13},
  journal   = {ACS applied materials \& interfaces / American Chemical Society},
  number    = {7},
  publisher = {American Chemical Society},
  address   = {Washington, DC},
  issn      = {1944-8244},
  doi       = {10.1021/acsami.1c00466},
  pages     = {8095 -- 8101},
  year      = {2021},
  abstract  = {Enzymes can support the synthesis or degradation of biomacromolecules in natural processes. Here, we demonstrate that enzymes can induce a macroscopic-directed movement of microstructured hydrogels following a mechanism that we call a "Jack-in-the-box" effect. The material's design is based on the formation of internal stresses induced by a deformation load on an architectured microscale, which are kinetically frozen by the generation of polyester locking domains, similar to a Jack-in-thebox toy (i.e., a compressed spring stabilized by a closed box lid). To induce the controlled macroscopic movement, the locking domains are equipped with enzyme-specific cleavable bonds (i.e., a box with a lock and key system). As a result of enzymatic reaction, a transformed shape is achieved by the release of internal stresses. There is an increase in entropy in combination with a swelling-supported stretching of polymer chains within the microarchitectured hydrogel (i.e., the encased clown pops-up with a pre-stressed movement when the box is unlocked). This utilization of an enzyme as a physiological stimulus may offer new approaches to create interactive and enzyme-specific materials for different applications such as an optical indicator of the enzyme's presence or actuators and sensors in biotechnology and in fermentation processes.},
  language  = {en}
}
@article{BehlBalkLuetzowetal.2021,
  author    = {Behl, Marc and Balk, Maria and L{\"u}tzow, Karola and Lendlein, Andreas},
  title     = {Impact of block sequence on the phase morphology of multiblock copolymers obtained by high-throughput robotic synthesis},
  series = {European polymer journal : EPJ},
  volume    = {143},
  journal   = {European polymer journal : EPJ},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0014-3057},
  doi       = {10.1016/j.eurpolymj.2020.110207},
  pages     = {9},
  year      = {2021},
  abstract  = {The chemical nature, the number length of integrated building blocks, as well as their sequence structure impact the phase morphology of multiblock copolymers (MBC) consisting of two non-miscible block types. We hypothesized that a strictly alternating sequence should favour phase segregation and in this way the elastic properties. A library of well-defined MBCs composed of two different hydrophobic, semi-crystalline blocks providing domains with well-separated melting temperatures (T(m)s) were synthesized from the same type of precursor building blocks as strictly alternating (MBCsalt) or random (MBCsran) MBCs and compared. Three different series of MBCsalt or MBCsran were synthesized by high-throughput synthesis by coupling oligo(e-caprolactone) (OCL) of different molecular weights (2, 4, and 8 kDa) with oligotetrahydrofuran (OTHF, 2.9 kDa) via Steglich esterification in which the molar ratio of the reaction partners was slightly adjusted. Maximum of weight average molecular weight (M-w) were 65,000 g center dot mol(-1), 165,000 g center dot mol(-1), and 168,000 g center dot mol(-1) for MBCsalt and 80,500 g center dot mol(-1), 100,000 g center dot mol(-1), and 147,600 g center dot mol(-1) for MBCsran. When Mw increased, a decrease of both Tms associated to the melting of the OCL and OTHF domains was observed for all MBCs. T-m (OTHF) of MBCsran was always higher than Tm (OTHF) of MBCsalt, which was attributed to a better phase segregation. In addition, the elongation at break of MBCsalt was almost half as high when compared to MBCsran. In this way this study elucidates role of the block length and sequence structure in MBCs and enables a quantitative discussion of the structure-function relationship when two semi-crystalline block segments are utilized for the design of block copolymers.},
  language  = {en}
}
@article{BehlBalkMansfeldetal.2021,
  author    = {Behl, Marc and Balk, Maria and Mansfeld, Ulrich and Lendlein, Andreas},
  title     = {Phase morphology of multiblock copolymers differing in sequence of blocks},
  series = {Macromolecular materials and engineering},
  volume    = {306},
  journal   = {Macromolecular materials and engineering},
  number    = {3},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {1439-2054},
  doi       = {10.1002/mame.202000672},
  pages     = {9},
  year      = {2021},
  abstract  = {The chemical nature, the number length of integrated building blocks, as well as their sequence structure impact the phase morphology of multiblock copolymers (MBC) consisting of two non-miscible block types. It is hypothesized that a strictly alternating sequence should impact phase segregation. A library of well-defined MBC obtained by coupling oligo(epsilon-caprolactone) (OCL) of different molecular weights (2, 4, and 8 kDa) with oligotetrahydrofuran (OTHF, 2.9 kDa) via Steglich esterification results in strictly alternating (MBCalt) or random (MBCran) MBC. The three different series has a weight average molecular weight (M-w) of 65 000, 165 000, and 168 000 g mol(-1) for MBCalt and 80 500, 100 000, and 147 600 g mol(-1) for MBCran. When the chain length of OCL building blocks is increased, the tendency for phase segregation is facilitated, which is attributed to the decrease in chain mobility within the MBC. Furthermore, it is found that the phase segregation disturbs the crystallization by causing heterogeneities in the semi-crystalline alignment, which is attributed to an increase of the disorder of the OCL semi-crystalline alignment.},
  language  = {en}
}
@article{BochoveGrijpmaLendleinetal.2021,
  author    = {Bochove, Bas van and Grijpma, Dirk W. and Lendlein, Andreas and Sepp{\"a}l{\"a}, Jukka},
  title     = {Designing advanced functional polymers for medicine},
  series = {European polymer journal : EPJ},
  volume    = {155},
  journal   = {European polymer journal : EPJ},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0014-3057},
  doi       = {10.1016/j.eurpolymj.2021.110573},
  pages     = {2},
  year      = {2021},
  language  = {en}
}
@article{BaeckemoLiuLendlein2021,
  author    = {B{\"a}ckemo, Johan Dag Valentin and Liu, Yue and Lendlein, Andreas},
  title     = {Bio-inspired and computer-supported design of modulated shape changes in polymer materials},
  series = {MRS communications / a publication of the Materials Research Society},
  volume    = {11},
  journal   = {MRS communications / a publication of the Materials Research Society},
  number    = {4},
  publisher = {Springer},
  address   = {Berlin},
  issn      = {2159-6867},
  doi       = {10.1557/s43579-021-00056-6},
  pages     = {462 -- 469},
  year      = {2021},
  abstract  = {The Venus flytrap is a fascinating plant with a finely tuned mechanical bi-stable system, which can switch between mono- and bi-stability. Here, we combine geometrical design of compliant mechanics and the function of shape-memory polymers to enable switching between bi- and mono-stable states. Digital design and modelling using the Chained Beam Constraint Model forecasted two geometries, which were experimentally realized as structured films of cross-linked poly[ethylene-co-(vinyl acetate)] supported by digital manufacturing. Mechanical evaluation confirmed our predicted features. We demonstrated that a shape-memory effect could switch between bi- and mono-stability for the same construct, effectively imitating the Venus flytrap.},
  language  = {en}
}
@article{DengWangXuetal.2021,
  author    = {Deng, Zijun and Wang, Weiwei and Xu, Xun and Ma, Nan and Lendlein, Andreas},
  title     = {Polydopamine-based biofunctional substrate coating promotes mesenchymal stem cell migration},
  series = {MRS advances : a journal of the Materials Research Society (MRS)},
  volume    = {6},
  journal   = {MRS advances : a journal of the Materials Research Society (MRS)},
  number    = {31},
  publisher = {Springer Nature Switzerland AG},
  address   = {Cham},
  issn      = {2059-8521},
  doi       = {10.1557/s43580-021-00091-4},
  pages     = {739 -- 744},
  year      = {2021},
  abstract  = {Rapid migration of mesenchymal stem cells (MSCs) on device surfaces could support in vivo tissue integration and might facilitate in vitro organoid formation. Here, polydopamine (PDA) is explored as a biofunctional coating to effectively promote MSC motility. It is hypothesized that PDA stimulates fibronectin deposition and in this way enhances integrin-mediated migration capability. The random and directional cell migration was investigated by time-lapse microscopy and gap closure assay respectively, and analysed with softwares as computational tools. A higher amount of deposited fibronectin was observed on PDA substrate, compared to the non-coated substrate. The integrin beta 1 activation and focal adhesion kinase (FAK) phosphorylation at Y397 were enhanced on PDA substrate, but the F-actin cytoskeleton was not altered, suggesting MSC migration on PDA was regulated by integrin initiated FAK signalling. This study strengthens the biofunctionality of PDA coating for regulating stem cells and offering a way of facilitating tissue integration of devices.},
  language  = {en}
}
@article{FarhanBehlKratzetal.2021,
  author    = {Farhan, Muhammad and Behl, Marc and Kratz, Karl and Lendlein, Andreas},
  title     = {Origami hand for soft robotics driven by thermally controlled polymeric fiber actuators},
  series = {MRS communications / a publication of the Materials Research Society},
  volume    = {11},
  journal   = {MRS communications / a publication of the Materials Research Society},
  number    = {4},
  publisher = {Springer},
  address   = {Berlin},
  issn      = {2159-6859},
  doi       = {10.1557/s43579-021-00058-4},
  pages     = {476 -- 482},
  year      = {2021},
  abstract  = {Active fibers can serve as artificial muscles in robotics or components of smart textiles. Here, we present an origami hand robot, where single fibers control the reversible movement of the fingers. A recovery/contracting force of 0.2 N with a work capacity of 0.175 kJ kg(-1) was observed in crosslinked poly[ethylene-co-(vinyl acetate)] (cPEVA) fibers, which could enable the bending movement of the fingers by contraction upon heating. The reversible opening of the fingers was attributed to a combination of elastic recovery force of the origami structure and crystallization-induced elongation of the fibers upon cooling.},
  language  = {en}
}
@article{FolikumahBehlLendlein2021,
  author    = {Folikumah, Makafui Y. and Behl, Marc and Lendlein, Andreas},
  title     = {Reaction behaviour of peptide-based single thiol-thioesters exchange reaction substrate in the presence of externally added thiols},
  series = {MRS communications / a publication of the Materials Research Society},
  volume    = {11},
  journal   = {MRS communications / a publication of the Materials Research Society},
  number    = {4},
  publisher = {Springer},
  address   = {Berlin},
  issn      = {2159-6859},
  doi       = {10.1557/s43579-021-00041-z},
  pages     = {402 -- 410},
  year      = {2021},
  abstract  = {Identification of patterns in chemical reaction pathways aids in the effective design of molecules for specific applications. Here, we report on model reactions with a water-soluble single thiol-thioester exchange (TTE) reaction substrate, which was designed taking in view biological and medical applications. This substrate consists of the thio-depsipeptide, Ac-Pro-Leu-Gly-SLeu-Leu-Gly-NEtSH (TDP) and does not yield foul-smelling thiol exchange products when compared with aromatic thiol containing single TTE substrates. TDP generates an alpha,omega-dithiol crosslinker in situ in a 'pseudo intramolecular' TTE. Competitive intermolecular TTE of TDP with externally added "basic" thiols increased the crosslinker concentration whilst "acidic" thiols decreased its concentration. TDP could potentially enable in situ bioconjugation and crosslinking applications.},
  language  = {en}
}
@article{FolikumahBehlLendlein2021,
  author    = {Folikumah, Makafui Yao and Behl, Marc and Lendlein, Andreas},
  title     = {Thiol-Thioester exchange reactions in precursors enable pH-triggered hydrogel formation},
  series = {Biomacromolecules : an interdisciplinary journal focused at the interface of polymer science and the biological sciences},
  volume    = {22},
  journal   = {Biomacromolecules : an interdisciplinary journal focused at the interface of polymer science and the biological sciences},
  number    = {5},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {1525-7797},
  doi       = {10.1021/acs.biomac.0c01690},
  pages     = {1875 -- 1884},
  year      = {2021},
  abstract  = {Bio-interactive hydrogel formation in situ requires sensory capabilities toward physiologically relevant stimuli. Here, we report on pH-controlled in situ hydrogel formation relying on latent cross-linkers, which transform from pH sensors to reactive molecules. In particular, thiopeptolide/thio-depsipeptides were capable of pH-sensitive thiol-thioester exchange reactions to yield a,co-dithiols, which react with maleimide-functionalized multi-arm polyethylene glycol to polymer networks. Their water solubility and diffusibility qualify thiol/thioester-containing peptide mimetics as sensory precursors to drive in situ localized hydrogel formation with potential applications in tissue regeneration such as treatment of inflamed tissues of the urinary tract.},
  language  = {en}
}
@article{FriessLendleinWischke2021,
  author    = {Friess, Fabian and Lendlein, Andreas and Wischke, Christian},
  title     = {Size control of shape switchable micronetworks by fast two-step microfluidic templating},
  series = {Journal of materials research},
  volume    = {36},
  journal   = {Journal of materials research},
  number    = {16},
  publisher = {Springer},
  address   = {Berlin},
  issn      = {0884-2914},
  doi       = {10.1557/s43578-021-00295-2},
  pages     = {3248 -- 3257},
  year      = {2021},
  abstract  = {Shape-memory polymer micronetworks (MN) are micrometer-sized objects that can switch their outer shape upon external command.This study aims to scale MN sizes to the low micrometer range at very narrow size distributions. In a two-step microfluidic strategy, the specific design of coaxial class capillary devices allowed stabilizing the thread of the dispersed phase to efficiently produce precursor particles in the tip-streaming regime at rates up to similar to 170 kHz and final sizes down to 4 mu m. In a subsequent melt-based microfluidic photocrosslinking of the methacrylate-functionalized oligo(epsilon-caprolactone) precursor material, MN could be produced without particle aggregation. A comprehensive analysis of MN properties illustrated successful crosslinking, semi-crystalline morphology, and a shape-switching functionality for all investigated MN sizes (4, 6, 9, 12, 22 mu m). Such functional micronetworks tailored to and below the dimension of cells can enable future applications in technology and medicine like controlling cell interaction.},
  language  = {en}
}