Active suspensions destabilise passive membranes

We present a theory for the interaction between active suspensions and a passive flexible membrane. By explicitly solving for the pressure exerted by the active particles, in the absence of phase separation, we show that they renormalise the membrane properties and introduce novel non-local contributions. The overall effect is destabilising, acting to reduce both the surface tension and bending modulus. This theory predicts the onset of instabilities their morphology in good agreement with experimental and simulation data.