Dynamic Light Scattering Measurements for Soft Materials on Solid Substrates: Employing Evanescent-wave Illumination and Dark-field Collection with a High Numerical Aperture Microscope Objective.

We developed an instrument that allows us to measure dynamic light scattering from soft materials on solid substrates by avoiding strong background due to the reflection light from substrates. In the instrument, samples on substrates are illuminated by evanescent-light field and the resultant scattered light from the samples is collected with a dark-field optical configuration by employing a high numerical aperture microscope objective. We applied the instrument to measure the dynamic properties of supported lipid bilayers (SLBs), which have been widely utilized in industries as functional materials such as biosensors. From the time course of the scattered light from the SLBs, the power spectrum with the broad peak ranging from 10 to 20 kHz is observed. The use of the microscope objectives enables us to apply the instrument to future light scattering imaging for dynamic properties of soft materials supported on various substrates by combining with conventional microscope systems.