Large-scale and continuous production of sodium alginate/MWCNTs axial heterogeneous fibers moisture-electric generator with visual identification of acid/alkali gases

Moisture electricity generator (MEG) is a green and environmental-friendly energy harvesting technology, and the ubiquitous presence of moisture makes it a strong competitor for mobile power. Among the available structural forms, fibrous MEG with engineered tunability and high integrality are perhaps one of the most promising solutions. However, the continuous preparation of fibrous MEG limits their scale-up production and commercial application. Herein, we utilized sodium alginate (SA) and multi-walled carbon nanotubes (MWCNTs) in combination with microfluidic sequential wet spinning to continuously fabricate axial heterogeneous structure fiber, where the gradient of oxygen-containing functional groups is critical for electricity generation. A single unit (1 cm) can produce an open-circuit voltage (V oc ) of 0.26 V, a short-circuit current (I sc ) of 2.59 μA, and a power density of 0.80 μW/cm 2 under moisture stimulation. The energy output can be easily increased by a simple series/parallel connection. Benefiting from the axial heterogeneous structure, the fibrous MEG can continuously output 0.2–0.25 V for more than 168 h. Furthermore, we extended the functionality and practicality of the fibrous MEG by incorporating materials with pH-responsive functions, which enables visual monitoring of acid/alkali gases. Overall, this work creates a new strategy for the structural design and large-scale continuous production of multifunctional fiber-based electronics.