Display omitted •We designed fully bioresorbable FF nanotube-based piezoelectric nanocomposite.•Self-assembled FF nanotubes provide high piezoelectric responses.•FEM simulation enabled rational selection of polymer matrices of FF nanotubes.•FF-based nanocomposites generate local piezoelectricity upon cell activity.•The local piezoelectricity can manipulate cell alignment and proliferation. Here we propose a material design for nanocomposites of self-assembled diphenylalanine (FF) nanotubes with bioresorbable polymer matrices to achieve a flexible and mechanically durable bio-piezoelectric nanogenerator (bio-PENG). The piezoelectric property of the nanocomposite membranes demonstrates a normal-like distribution in accordance with Young’s modulus of the polymer matrices. Attributed to the high conformability between polyvinyl alcohol (PLA) and FF nanotubes, the PLA-based nanocomposite bio-PENG exhibits high electrical output performance, reaching an output voltage of 2.8 V and power density of 2.6 μW cm−2. Moreover, the bio-PENG shows stable energy-generating performance for over 1000 operating cycles. Benefiting from the high piezoelectric property, the nanocomposite can manipulate cell activities including alignment and proliferation. The results of the simulation using the finite element method (FEM) confirm that the nanocomposite can generate piezoelectricity through mechanical strain caused by free migration of cells. In vitro demonstration shows that cell migration-induced piezoelectricity allows for the manipulation of cell alignment and proliferation. Thus, our material design of FF nanotube-based nanocomposites presents a promising option for bioresorbable energy harvesters that will be widely available in biomedical applications.