Chain Dynamics in Supramolecular Polymer Networks

Supramolecular polymer networks consist of macromolecules that are cross linked by transient physical interactions such as hydrogen bonding or transition metal complexation. The utility of these networks is based on their mechanical properties, which lay between those of permanent networks and that of mechanically entangled, viscoelastic polymer solutions, depending on the strength of transient chain cross linking. To benefit from this interplay, it is necessary to understand it. To promote this understanding, we use a modular toolkit to form supramolecular polymer networks that exhibit greatly varying strength of transient chain cross linking but that are all derived from the very same precursor polymer. This strategy allows the impact of the strength of transient chain cross linking on the network dynamics and mechanics to be studied with high consistency. We follow this approach to evaluate the diffusive mobility of labeled tracer chains within these transient networks. Our results reveal that the concentration dependence of the tracer chain diffusivity is in agreement with theoretical predictions derived from the sticky reptation model by Rubinstein and Semenov, provided the chain association is stronger than a certain threshol

Implementation of anisotropic soft pads in a surgical gripper for secure and gentle grip on vulnerable tissues

Current surgical grippers rely on friction grip, where normal loads (i.e. pinch forces) are translated into friction forces. Operating errors with surgical grippers are often force-related, including tissue slipping out of the gripper because of too low pinch forces and tissue damaging due to too high pinch forces. Here, we prototyped a modular surgical gripper with elastomeric soft pads reinforced in the shear direction with a carbon-fiber fabric. The elastomeric component provides low normal stiffness to maximize contact formation without the need of applying high normal loads (i.e. pinch forces), whereas the carbon-fiber fabric offers high shear stiffness to preserve the formed contact under the lateral loads (i.e. shear forces) that occur during tissue lifting. Additionally, we patterned the pads with a sub-surface micropattern, to further reduce the normal stiffness and increase shear stiffness. The body of the prototype gripper, including shaft, joints, and gripper tips, was fabricated in a single step using 3D printing, followed by manual attachment of the soft pads to the gripper. The gripping performance of the newly developed soft gripper on soft tissues was experimentally compared to reference grippers equipped with metal patterned pads. The soft-pad gripper generated similar gripping forces but significantly lower pinch forces than metal-pad grippers. We conclude that grippers with anisotropic-stiffness pads are promising for secure and gentle tissue grip.</p

A modular construction kit for supramolecular polymer gels

Supramolecular polymer gels are swollen networks of macromolecules interconnected by transient, non covalent bonds; they form an extraordinarily useful class of soft, stimuli sensitive materials. To optimize the use of supramolecular polymer gels in applications, their physical and chemical properties must be understood. This understanding is ideally achieved using model systems that allow the type and strength of supramolecular chain crosslinking to be varied to a great extent without concurrent alteration of the properties of the covalent polymer backbones. We introduce a system that provides these requirements. We use linear chains of electrophilic methacryl succinimidyl MASI modified poly N isopropylacrylamide pNIPAAm . These polymers can be modified in a modular fashion by replacing their electrophilic MASI units by nucleophilic amine functionalized derivatives of custom, supramolecular crosslinkable functionalities. We follow this approach and prepare a set of pNIPAAm polymers that consist of exactly the same polymer backbone functionalized with different types of crosslinkable sidegroups. These polymers are then crosslinked by addition of low molecular weight linkers that are complementary to the motifs on the polymer. We use multiple hydrogen bonding based on diaminotriazine and maleimide, cyanuric acid and Hamilton wedges, and diaminotriazine and cyanuric acid; we also use metal complexation based on terpyridine and different metal salts. This approach creates supramolecular networks of greatly varying rheological properties, from low viscous liquids to elastic gels, each showing consistent and quantitative correlation between the gel mechanical properties and the binding strength of the respective constituent supramolecular crosslinking motifs. Exploiting the good solubility of the common pNIPAAm backbone polymer in a variety of solvents allows these networks to be prepared and studied in different media with unprecedented consistency and flexibilit

Implementation of anisotropic soft pads in a surgical gripper for secure and gentle grip on vulnerable tissues

Current surgical grippers rely on friction grip, where normal loads (i.e. pinch forces) are translated into friction forces. Operating errors with surgical grippers are often force-related, including tissue slipping out of the gripper because of too low pinch forces and tissue damaging due to too high pinch forces. Here, we prototyped a modular surgical gripper with elastomeric soft pads reinforced in the shear direction with a carbon-fiber fabric. The elastomeric component provides low normal stiffness to maximize contact formation without the need of applying high normal loads (i.e. pinch forces), whereas the carbon-fiber fabric offers high shear stiffness to preserve the formed contact under the lateral loads (i.e. shear forces) that occur during tissue lifting. Additionally, we patterned the pads with a sub-surface micropattern, to further reduce the normal stiffness and increase shear stiffness. The body of the prototype gripper, including shaft, joints, and gripper tips, was fabricated in a single step using 3D printing, followed by manual attachment of the soft pads to the gripper. The gripping performance of the newly developed soft gripper on soft tissues was experimentally compared to reference grippers equipped with metal patterned pads. The soft-pad gripper generated similar gripping forces but significantly lower pinch forces than metal-pad grippers. We conclude that grippers with anisotropic-stiffness pads are promising for secure and gentle tissue grip.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Medical Instruments & Bio-Inspired Technolog

Plastic zonder olie : lesmodule voor nieuwe scheikunde

Lesmodule voor nieuwe scheikunde voor leerlingen uit 5 en 6 vwo. Bioplastics worden gemaakt uit natuurlijke grondstoffen. Als ze de synthetische plastics vervangen kan de voorraad aardolie ontzien worden. Omdat veel bioplastics afbreekbaar zijn, kan ook de berg plastic afval krimpen. Maar zijn bioplastics in staat om ons de reguliere plastics te doen vergeten? Hoe maken we bioplastics met dezelfde veelzijdige eigenschappen als plastic? Waar komen de uiteenlopende eigenschappen van plastics eigenlijk vandaan? De lesmodule ‘Plastic zonder Olie’ gaat op deze en meerdere vragen in. Naast de practica waarin de leerlingen bioplastics gaan maken ligt het zwaartepunt van de module bij een multidisciplinaire slotopdracht

Plastic zonder olie : lesmodule voor nieuwe scheikunde

Lesmodule voor nieuwe scheikunde voor leerlingen uit 5 en 6 vwo. Bioplastics worden gemaakt uit natuurlijke grondstoffen. Als ze de synthetische plastics vervangen kan de voorraad aardolie ontzien worden. Omdat veel bioplastics afbreekbaar zijn, kan ook de berg plastic afval krimpen. Maar zijn bioplastics in staat om ons de reguliere plastics te doen vergeten? Hoe maken we bioplastics met dezelfde veelzijdige eigenschappen als plastic? Waar komen de uiteenlopende eigenschappen van plastics eigenlijk vandaan? De lesmodule ‘Plastic zonder Olie’ gaat op deze en meerdere vragen in. Naast de practica waarin de leerlingen bioplastics gaan maken ligt het zwaartepunt van de module bij een multidisciplinaire slotopdracht