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FRINATEK-Fri prosj.st. mat.,naturv.,tek

Dynamics of coupled processes in responsive soft (bio)polymer materials

Alternative title: Dynamikk til koblede prosesser i responsive polymer materialer.

Awarded: NOK 8.0 mill.

The project Dynamics of coupled processes in responsive soft (bio)polymer materials (DynaRes) focuses on development of novel insight into the dynamics of responsive soft (bio)polymer materials that respond to molecular stimuli. Within the DynaRes project we focus on the dynamics of the coupled processes of molecular probe transport, recognition by interaction, reaction, hydrogel structure and network relaxation, occurring in such materials. This approach goes beyond the extensive studies of responsive (bio)polymer materials that mainly uses correlations between the stimuli and hydrogel structure and composition and resulting changes in equilibrium swelling states as the primary observable. DynaRes combines experimental and numerical strategies. In the project, hydrogels with embedded duplex DNA segments as physical crosslinks, a soft material offering large parameter space for its properties, as well as being applicable for biosensors is studied. The experimental approaches include preparation of various hydrogel entities, spatiotemporal characterization of the different processes utilizing fluorescence techniques, and high-resolution interferometry. The spatiotemporal evolution of the processes, involving coupling to elastic properties, will be modelled using finite element. Experimental protocols is realised and applied for fluorescence labelling for spatiotemporal characterization of molecular processes, mechanically stratified hydrogels for determination of kinetics of wrinkle formation in responsive hydrogels, and numerical procedures as needed for the modelling of the swelling processes. Application of fluoroprobes has shown how the reaction-diffusion processes mutually interact in the case of oligonucleotides interaction with embedded DNA crosslinks in the hydrogels. The oligonucleotides that binds strongly to the embedded DNA crosslinks and subsequently open them in a competitive displacement, is at the same time drained from the invading pool of oligonucleotides, yielding an overall plug like concentration profile moving (slowly) through the hydrogel. On the other hand, the weakly binding oligonucleotides fills up the whole gel volume apparently like a diffusive dominated process. Hydrogels with embedded DNA crosslinks selected among reported aptamers has been realized as biosensors. The protocol for the mechanically stratified hydrogels is based on spin-coating of various polymer systems of responsive hydrogels, with varying concentrations of monomer and cross linker for creating two layers of different Young's modulus and thicknesses. These materials, including also monitoring wrinkle formation are characterized employing quantitative phase imaging (QPI) and confocal microscopy. For the numerical analysis of hydrogel swelling behavior, two different models have been implemented in FORTRAN as user subroutines for the commercial finite element software Abaqus; one simple model where the chemical potential directly drives the swelling behavior and one more complex model accounting for the specific processes occurring in cationic gels. The chemical potential driving the swelling of the gels have been included in the model utilizing the similarities between hydrogel swelling and heat transfer, enabling the temperature elements of Abaqus to be used to mimic the diffusion process in gels. The simple model is used to study the onset of buckling in layered hydrogels with stiffness gradients during transient swelling. Efficient post-processing procedures have been established to quantify the swelling ratio and wavelength at the onset of buckling from numerical results. The heterogeneous nature of the swelling process significantly alters the predicted swelling level at the onset of buckling in layered hydrogels, with lower global swelling ratios at the onset of buckling. This behavior is seen for various stiffness values for the substrate and stiffness contrast between the substrate and the film. The results obtained for homogeneous swelling using the finite element approach are compared with reported semi-analytical results, demonstrating good agreement for both the extent of swelling at instability and the wavelength. We are currently working on extending the available semi-analytical procedure to heterogenous swelling situations and to implement the solution process in Python. This represent a benchmark related for the finite element simulations and is furthermore a computationally efficient open-source alternative to finite element simulations. The cationic model has been used to obtain representative material parameters for transient hydrogel swelling by an inverse modeling routine comparing simulation results with qualitative data from the interferometric experimental setup. This approach has also been combined with specific ion effects encountered at higher salt concentrations where the salt-specific effect is represented as specific Flory-Huggins interaction parameters.

I prosjektet er det oppnådde ny fundamental kunnskap med hensyn til samspillet mellom ulike prosesser knyttet til molekylære responsive hydrogeler. Dette er kunnskap som kan legges til grunn for mer hensiktsmessig design av slike materialer ved anvendelse som biosensorer, og et «proof of concept» for det er vist. Videre er det oppnådd ny kunnskap om forekomst av rynking i mekanisk heterogene hydrogeler. Dette er et fenomen som andre har beskrevet til å være av betydning i forbindelse med folding av myke materialer slik de forekommer i morfogenese. Samlet sett resulterer dette i et kunnskapsgrunnlag en kan bygge videre på, som har potensiell oppmerksomhet i internasjonale forskningsmiljøer og som kan anvendes ved utvikling av biosensorer.

The project Dynamics of coupled processes in responsive soft (bio)polymer materials (DynaRes) focuses on development of novel insight into the dynamics of responsive soft (bio)polymer materials that respond to molecular stimuli. Within the DynaRes project we focus on the dynamics within the coupled processes of molecular probe transport, recognition by interaction, reaction, hydrogel structure and network relaxation, occurring in such materials. This approach goes beyond the extensive studies of responsive (bio)polymer materials that mainly uses correlations between the stimuli and hydrogel structure and composition on one hand, and resulting changes in equilibrium swelling states on the other, as the primary observable. The DynaRes approach is to combine experimental and numerical strategies to assess the dynamics of the various processes taking place in two selected molecular responsive hydrogels. The selected hydrogels, the first include one with embedded duplex DNA segments as physical crosslinks, and the other including a host-guest type crosslink, represent models offering large parameter space for their properties, as well as being applicable for biosensors. The experimental approaches include preparation of various hydrogel entities, spatiotemporal characterization of the different processes utilizing fluorescence techniques, and high resolution interferometry. The spatiotemporal evolution of the processes, involving coupling to elastic properties, will be modelled using finite element based approaches. Successful implementation of the DynaRes project can be expected to provide significant advancement in knowledge of biomolecule responsive hydrogel materials, not only for the selected the soft materials, but also with relevance for other man made hydrogels or as existing naturally.

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FRINATEK-Fri prosj.st. mat.,naturv.,tek