Unravelling what governs the fluctuation spectra of active membranes

We detect thermal and activity-driven fluctuations of lipid vesicles over the exceptionally broad frequency range of 0.1 to 1,000 Hz with an amplitude resolution of 0.1 nm. Thermal fluctuations, understood phenomenologically from the classical Helfrich theory, are modified by active protein pumps to enhance high-frequency fluctuations. This enhancement yields surprises regarding underlying processes occurring in the membrane.