Ricerca CERCA

3D Printing of Granular Hydrogels

azienda Thesis in external company    estero Thesis abroad



External reference persons Matteo Hirsch, prof. Esther Amsted - EPFL Lausanne (CH)

Research Groups AA - Materials and Processes for Micro and Nano Technologies


Description Hydrogels are among the first biomaterials expressly designed for their use in biomedicine.
However, state-of-the-art applications of hydrogels are severely limited because of their mechanical properties. Most hydrogels are either too soft or too brittle to be used for load-bearing applications. To overcome this shortcoming, double network (DN) hydrogels composed of two interpenetrating polymeric networks have been introduced. These DN hydrogels are composed of a highly crosslinked network, the filler, responsible for the stiffness of the hydrogel and a second
loosely crosslinked one, the matrix, that regulates the toughness of the material. Despite this great improvement in mechanics, composition and structural complexity found in soft natural tissues remain yet to be matched. Indeed, soft natural materials possess locally varying compositions and structures that are well-defined over many length scales. By contrast, synthetic hydrogels typically have an ill-defined microstructure and their composition is most often homogeneous. To obtain a better structural control, we introduced a novel 3D printing approach to fabricate strong and tough soft materials, namely double network granular hydrogels (DNGHs).[1] This is achieved with an ink composed of microgels that are swollen in a monomer-containing solution. Upon printing and post-curing, the monomers are converted into a percolating network, yielding a solid DNGH. These DNGHs possess mechanical properties that are superior to reported additive manufactured hydrogels. Because this new technology employs a microgel-based ink, it significantly extends the choice of materials that can be additive manufactured. Moreover, the modularity of the jamming approach allows for the combination of different inks in the same printing process, resulting in mechanically robust stimuli responsive structures. In this project, microgels will be composed of a variety of biocompatible polymers. In the first part, you will investigate the influence of the synthesis route on the mechanical and rheological properties of the resulting DNGHs. To achieve this goal, you will produce different types and sizes of microgels. The second part of the project is devoted to introducing microstructures into hydrogels. You will test the influence of type, density, and distribution of different monomer types on their overall mechanical properties. In the final part of the project, you will investigate the possibility to vary the local composition by means of multi-nozzle extrusion printing and harness it for the fabrication of 3D printed heterogeneous DNGHs that mimic soft load-bearing natural tissues (i.e. cartilage, meniscus, vertebral disk).

See also  thesis proposal 2021_ea.pdf 

Required skills A successful candidate is a motivated, self-driven person that likes to work on challenging projects
in an interdisciplinary, collaborative, friendly atmosphere. They have good background in
chemistry, chemical engineering, materials science, nanotechnology, or relate disciplines.

Notes If you are interested, please, send the CV and a short motivation letter to matteo.hirsch@epfl.ch.
Reference bibliography M. Hirsch, A. Charlet, E. Amstad, Adv. Funct. Mater. 2021, 31, 2005929

Deadline 09/02/2022      PROPONI LA TUA CANDIDATURA

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