Printable embedded pattern designs affect mechanical performance of cold-water fish gelatin cast films

Edible films made of cold-water fish gelatin suffer from suboptimal mechanical strength, limiting their use for sustainable packaging applications. In this study, the use of 3D-printable embedded patterns is investigated as reinforcement for gelatin cast films, aiming for cast films with customizable and enhanced mechanical strength. Various combinations of patterns (i.e. lines, grids, and triangles) and inks (varying concentrations of sodium caseinate, sodium alginate, and cellulose fibers) were 3D-printed. The 3D-printed structures were embedded into cast films and the mechanical properties were subsequently tested. Our results show that films with embedded patterns had an overall higher tensile strength at different stretching directions (i.e. parallel, perpendicular, and diagonal), compared to the plain gelatin films. The strongest mechanical anisotropy was found using the line pattern and the grid showed anisotropy in the parallel and perpendicular direction, highlighting the influence of printing path. Microscopical analysis revealed that embedded patterns affected the fracture mechanics of films. Interestingly, cellulose fibers showed alignment in the printed filaments along the printing direction, which contributes to an increased tensile strength of films after drying. Thus, by using printable embedded pattern design, edible films with customized mechanical performance can be made, contributing to future developments of sustainable packaging solutions. • Embedded patterns increase the tensile strength of gelatin films. • Degree of reinforcement depends on pattern design and stretching direction. • Embedded line pattern shows the strongest mechanical anisotropy. • Cellulose fibers strengthen filaments by inducing alignment during printing.