Sahin, M. A.; Stoecklein, D.; Park, J.; Destgeer, G.

Microstructures created with flow lithography exhibit distinct functionality depending on the shape and composition of the precursor fluids, enabling applications from tissue engineering to anti-counterfeiting. However, current techniques rely on static nozzle geometries or passive hydrodynamic focusing, which commit to a fixed structure and limit dynamic reconfiguration of material architecture during fabrication. Here, we introduce ActiSculpt, an acoustofluidic platform that replaces in-channel physical structures with programmable, electronically driven acoustic streaming. By exploiting the interplay between laminar stability and acoustic streaming, we decouple deterministic fluid deformation from chaotic mixing, achieving a continuous cross-sectional displacement sensitivity of ~15 um/V. We demonstrate the generation of a diverse library of hydrogel particles whose cross-sectional moments of inertia are tunable up to 5.5-fold, establishing a direct, geometry-mediated link between acoustic parameters and the moments that govern bending and torsional rigidity. We further demonstrate continuous fiber fabrication in which acoustic parameters are varied in real time, encoding structural variation along the fiber's length. The result is a platform that overcomes the one-device, one-geometry constraint of existing techniques, enabling not only on-demand reconfiguration between fabrication runs but also real-time control of material architecture. This spatiotemporal control establishes a new design axis for soft-material manufacturing.