A novel method for measuring dynamic contact angles of fibers with spindle-knots

摘要

The determination of the dynamic contact angle is of significant interest for the characterization of the wettability of technical fibers and textiles in diverse fields of science and technology. There exist traditional methods for dynamic contact angle measurements of flat surfaces and of fibers with a uniform cross-sectional shape along the fiber. So far, however, no method has been reported which is suitable for structured fibers, particularly for spindle-knotted structured fibers of varying cross-sections. This article describes a new method for measuring the dynamic contact angle for polydimethylsiloxane (PDMS) spindle-knotted structured fibers. The method is an outcome of integrating the results obtained from experiments (applying force tensiometry) and a proposed theoretical model describing such fibers. The reliability and conformity of the results are shown by comparing the measured dynamic contacts angle of PDMS as spindle-knot and as a flat surface. This method may pave the road for better wettability analysis of various structured fibers. It also allows to measure the local receding and advancing contact angles for macroscopic/microscopic structured fibers (especially when they are not accessible as flat surfaces) against the various test liquids.