Direct‐Ink‐Writing <scp>3D</scp> Printing of <scp>PVDF</scp> / <scp>ILs</scp> @ <scp>CNTs</scp> Composites for Enhanced Piezoelectric Energy Harvesting

ABSTRACT Polyvinylidene fluoride (PVDF) is a promising piezoelectric polymer for energy harvesting and sensing, yet its application is limited by low polar‐phase content and challenges in fabricating complex geometries. Here, we report a mild‐condition direct ink writing (DIW) 3D printing strategy to fabricate PVDF nanocomposites incorporating multi‐walled carbon nanotubes (CNTs) functionalized with imidazolium ionic liquid (ILs). The DIW‐printability, thermal behavior, crystalline phase evolution, dielectric response, and cross‐sectional morphology are systematically investigated by TEM, rheology, DSC, XRD, FTIR, and SEM tests. The as‐prepared inks exhibit typical shear‐thinning behavior with a rapid thixotropic recovery within the linear viscoelastic region, enabling smooth extrusion and reliable deposition during the DIW process. Structural characterization shows a non‐monotonic dependence on the ILs content, with the β‐phase fraction reaching 86.15% and the crystallinity 41.62%. Under an impact acceleration of 5 m/s 2 , the optimal printed sample delivers 16.8 V open‐circuit voltage and 258 nA short‐circuit current, charges a 1 μF capacitor to 3.1 V within 300 s, and powers five LEDs. The device exhibits excellent stability, maintaining consistent output over 200 impact cycles. The device also serves as a flexible sensor, producing clear and repeatable voltage signatures under finger tapping and fist hammering, underscoring its potential for wearable biomechanical monitoring. These results demonstrate that DIW provides a practical and geometry‐customizable route to high‐performance PVDF piezoelectric devices.