Programmable Knot Microfibers from Piezoelectric Microfluidics

Abstract Microfibers have demonstrated significant application values in a large number of areas. Current efforts focus on developing new technologies to prepare microfibers with controllable morphological and structural features to enhance their functions. Here, a piezoelectric microfluidic platform is presented for consecutive spinning of functional microfibers with programmable spindle‐knots. In this platform, a jet of a pregel‐solution flowing in the channel can be subjected to a programmable piezoelectric signal and vibrates synchronously. Following a rapid polymerization of the wavy jet, microfibers with corresponding morphologies can be generated, including uniform, gradient, and symmetrical knots. Such a unique knot structure contributes to a water‐collection mechanism. Thus, it has been observed that microfibers with programmed knots enable even more flexible droplet handling and active water transport. In addition, by constructing higher‐order knot fiber networks, practical applications including spray reaction, lab‐on‐a‐chip vapor detection, etc., can also be demonstrated. it is believed that this platform opens a new avenue for fiber spinning, and the programmable microfibers would be highly applicable in chemical, biomedical, and environmental areas.