To evaluate the effect of ethanol on the liposome structure, the ethanol concentration in the liposome suspension should be gradually increased, depending on the measurement time, and thus, the use of a typical stopped-flow system is unsuitable. In addition, the time scale of liposome formation is nanoseconds and conventional SAXS does not exhibit a sufficient temporal resolution. Therefore, we measured and simulated the change in the liposome structure during the reverse process of liposome formation, i.e., liposome deformation, with a gradual increase in ethanol concentration. The time-resolved microfluidic-based SAXS measurement system, with a flowfocusing microchannel, is shown in Figure . To measure the structural dynamics of the liposomes using ethanol, the ethanol concentration in the liposome suspension should be gradually increased, depending on the residence time. In the microchannel, ethanol molecules are transported from the side-flow stream to the center stream via Fick's law of diffusion. Ethanol induces structural changes in the liposomes, depending on the increase in the ethanol concentration. The flow conditions and dimensions of the microchannel affect the ethanol diffusion behavior and signal-tonoise (S/N) ratio of the X-ray scattering intensity, and thus, we performed preliminary SAXS to optimize the flow conditions and microchannel structure. A total flow rate of 50 µL/min and a flow rate ratio (FRR) of the side channels to the center channel of 5 are suitable for observing the change in liposome structure with a high S/N ratio. The dimensions of the microchannel are optimized to 1 mm wide and 0.7 mm deep.