methods are disclosed in which a micelle is stabilized against degradation upon dilution . the micelle comprises molecules of a block polymer having a hydrophobic block and a hydrophilic block . the hydrophobic block forms a core of the micelle with corona from the hydrophilic block . the methods for stabilizing the core are by chemically cross - linking , incorporating a hydrophobic oil in the core to render it more hydrophobic and stable , and incorporating a cross - linked interpenetrating network of a stimuli - responsive hydrogel into the core . the hydrogel is responsive to any stimuli , but preferably temperature or ph . a substance such as , drugs , can be incorporated into the dense inner core of the micelles . when subjected to ultrasound , the micelles release the substance , and then reversibly revert to a stable dense core and re - encapsulating the substance when the ultrasound is turned off . by pulsing the ultrasound , it is therefore , to controllably release the substance in a pulsed manner corresponding to the ultrasound signal .