Altering the bubble release of reactive inkjet printed silk micro-rockets

A novel approach of using layer-by-layer (LBL) reactive inkjet printing (RIJ) of regenerated silk fibroin (RSF) was used to generate micron-sized silk rockets which have the enzyme catalase immobilised inside the silk scaffold structure and use the catalase enzyme to drive their motion in samples containing H2O2 as a fuel. By using the LBL printing approach we show that is it possible to generate 3D structures where different materials can be incorporated into the structure at defined locations. The use of silk together with an inkjet printing method has great potential to easily incorporate different enzymes, proteins, chemicals or other biomolecules and build versatile devices by entrapping them into the silk scaffold. This allows us to generate small-scale devices that can generate thrust via catalytic reactions within fluidic environments for potential applications including environmental monitoring and remediation, in vivo drug delivery and repair, and lab-on-a-chip diagnostics. In contrast, current manufacturing processes of micromotors often use slow and lengthy production processes (e.g. evaporation) combined with expensive materials such as platinum. The location of catalyst on these devices has been shown to influence trajectory behaviour, which is not easy to control using conventional methods. Furthermore devices using platinum as a catalyst can undergo biofouling thus inhibiting their catalytic reactions. By using biocompatible silk scaffolds, created by RIJ, the devices generated here have the potential to overcome all these problems.