Hydrogels prepared from low molecular weight gelators (LMWGs) are formed as a result of hierarchical intermolecular interactions between gelators to form fibres, and then further interactions between the self-assembled fibres via physical entanglements, as well as potential branching points. These interactions can allow hydrogels to recover quickly after a high shear rate has been applied. There are currently limited design rules describing which types of morphology or rheological properties are required for a LMWG hydrogel to be used as an effective, printable gel. By preparing hydrogels with different types of fibrous network structures, we have been able to understand in more detail the morphological type which gives rise to a 3D-printable hydrogel using a range of techniques, including rheology, small angle scattering and microscopy.

Although there is extensive literature covering the biomedical applications of superparamagnetic iron oxide nanoparticles (SPIONs), the phase of the iron oxide core used is not often taken into account when cell labelling and tracking studies for regenerative medicine are considered. Here, we use a co-precipitation reaction to synthesise particles of both magnetite- (Fe₃O₄) and maghemite- (γ-Fe₂O₃) based cores and consider whether the extra synthesis step to make maghemite based particles is advantageous for cell tracking.

Supramolecular gels have potential in many areas. In many cases, a major drawback is that the gels are formed at a high rate. As a result, non-optimal, kinetically trapped self-assembled structures are often formed, leading to gels that can be hard to reproduce and control. One method to get around kinetic trapping is annealing. Thermal annealing is one possi-bility, but it is not always desirable to heat the gels. Here, we describe a method to anneal pH-triggered gels after they are formed. We employ a reaction relay in a peptide-based hydro-gel system to anneal the structures by a controlled and uniform pH change. Our method allows us to prepare gels with more controlled properties. We show that this can be used to enable homogeneous ‘moulding and casting’ of the hydrogels. This method of annealing is more effective in improving gel robust-ness than a conventional heat-cool cycle.

We describe rheological protocols to study layered and three-dimensional (3D)-printed gels. Our methods allow us to measure the properties at different depths and determine the contribution of each layer to the resulting combined properties of the gels. We show that there are differences when using different measuring systems for rheological measurement, which directly affects the resulting properties being measured. These methods allow us to measure the gel properties after printing, rather than having to rely on the assumption that there is no change in properties from a preprinted gel. We show that the rheological properties of fluorenylmethoxycarbonyl-diphenylalanine (FmocFF) gels are heavily influenced by the printing process.

Annealing is widely used as a means of changing the physical properties of a material. The rate of heating and cooling used in the annealing process controls the final properties. Annealing can be used as a means of driving towards the, or at least a, thermodynamic minimum. There is surprisingly little information on annealing kinetically-trapped supramolecular gels. Here, we show that annealing multicomponent gels can be used to prepare materials with tunable mechanical properties. We show that annealing in a two-component gel leads to a self-sorted network, which has significantly different mechanical properties to the as-prepared gels. Whilst the fibres are self-sorted, we show that the annealing of this system leads to significant change in the network level of assembly, and it is this that leads to the increase in storage modulus. We also show that it is possible to selectively anneal only a single component in the mixture.

We show that combining cavitation and conventional rheology can be used to understand the underlying microstructure in gels.