The role of electrolysis and enzymatic hydrolysis treatment in the enhancement of the electrochemical properties of 3D-printed carbon black/poly(lactic acid) structures
Additive manufacturing, also known as 3D printing, is beginning to play an unprecedented role in developing many applications for industrial or personalized products. The conductive composite structures require additional treatment to achieve an electroactive surface useful for electrochemical devices. In this paper, the surfaces of carbon black/poly(lactic acid) CB-PLA printouts were activated by electrolysis or enzymatic digestion with proteinase K, or a simultaneous combination of both. The proposed modification protocols allow the tailoring of electrochemically active surfaces and electron transfer kinetics determined by electrochemical techniques (CV, EIS) by [Fe(CN)6]4-/3- redox probe. X-ray photon spectroscopy and SEM imaging were applied to determine the delivered surface chemistry. CB-PLA hydrolysis under alkaline conditions and anodic polarization greatly impacted the charge transfer kinetics. The enzymatic hydrolysis of PLA with proteinase K led to highly efficient results, yet requires an unsatisfactory prolonged activation duration of 72 h, which can be efficiently reduced by electrolysis carried out in the presence of the enzyme. Our studies hint that the activation protocol originates from surface electropolymerization rather than a synergistic interaction between the electrolysis and enzymatic hydrolysis. The detailed mechanism of CB-PLA hydrolysis supported by electrolysis is a promising new route to achieve time-efficient and environmentally-friendly activation procedure.