Efficient fractionation of cellulose nanofibers using spiral microchannel

Abstract

Plant fiber isolated cellulose nanofibers (CNFs) are the materials with excellent mechanical properties. However, application of CNFs in polymer reinforcement is normally unsatisfactory due to its intertwined size distribution. Efforts to produce uniform sized CNFs have yet to be studied. In present work, spiral microchannel was used to fractionate CNFs based on the balance between inertial lift force (FL) and Dean drag force (FD) exerted on CNFs. The results showed that the smaller length of CNFs equilibrated near the inner microchannel while the larger length of CNFs occupied the equilibrium position away from the inner wall. With the increase of flowrates from 50 to 220 μL/min, fractionation efficiency between inner and middle outlet (EIM) of spiral microchannel A with larger radius curvature (R) from 5 to 15 mm increased from 0 to 75.4%. However, stronger Dean flow attributing to decrease of R (3 mm to 10 mm) of single spiral microchannel B enabled satisfactory fractionation efficiency of 70.9% at flowrate of 90 μL/min. Moreover, the fractionation efficiency of double spiral microchannel with twice as length as microchannel A and three times as length as microchannel B was lower than that of single spiral microchannel at flowrate lower than 90 μL/min. Furthermore, this study exhibited a versatile and simple method for CNFs fractionation with high fractionation efficiency.