Aligned perylene bisimide hydrogels: a 3D printing approach to mechanophotoconductive films.

Organic electronics often require molecular alignment to facilitate efficient charge transport. However, existing alignment methods (e.g., magnetic alignment, dielectrophoresis, spin coating, and doctor blading) are energy-intensive, incompatible with water-based materials, or wasteful. Here, we demonstrate that extrusion-based 3D printing induces significant shear alignment in aqueous perylene bisimide (PBI) and poly(ethylene oxide) (PEO) blends, eliminating the need for external fields or incompatible coating techniques. Upon drying, the resultant xerogels retain this alignment, yielding homogeneous, conductive, flexible films. These films exhibit robust mechanophotoresponsive behaviour: bending the aligned fibres to a radius of 45 mm enhanced the photocurrent response by 2.5-fold compared to the unbent state. Furthermore, the films maintained structural integrity over 1000 bending cycles, retaining 50% of their photoresponse. This work establishes 3D printing as an accessible route to fabricate aligned, water-processed organic materials for wearable mechanophotoresponsive applications.