Microfluidic Printheads for Highly Switchable Multimaterial 3D Printing of Soft Materials

Abstract Extrusion‐based 3D printing uses multiple printing nozzles to produce multimaterial combinations. It requires complex alignment and accuracy control as well as an effective start‐stop procedure to print intermittently, which has so far proven difficult to achieve. A recently developed simpler approach is to sequence the multimaterial inks through a single nozzle that will avoid both of these requirements. Although it has been successfully demonstrated for viscoelastic inks, adapting it to more widely available viscous inks is still a challenge. Here, a dynamically controllable multimaterial single‐nozzle 3D printing printhead is demonstrated that is capable of printing both viscous and viscoelastic materials. It uses pneumatically pulsed injection of multiple viscous inks into a central nozzle for printing. It is shown through simulations and experiments that a crucial but narrow range active reverse pressure in static reservoir(s) is essential to provide accurate switching in viscous inks, which is unlike viscoelastic inks that have a wider operating range and do not require a backflow control. Using this approach, high frequency and fast switching between four different viscous materials for pixelated printing of different materials which can be used to embed different functional properties in a variety of 2D and 3D shapes using commercially available polymers are demonstrated.