Total automation of static and dynamic light scattering experiments with the aid of a special purpose robot

Abstract

A fully automated laser light scattering apparatus has been built and is now operational. A specially designed robot moves samples from a thermostatted holding rack to the spectrometer water bath. Use of a smoothly operating robot enables the study of multiphase fluids without disturbing sensitive interfaces. A computer controls virtually all the supporting hardware. Laser input intensity is adjusted by a rotating polarizer and the scattering angle is varied by a stepper motor built into the goniometer. Fiber optics and a silicon photodetector are employed to determine incident and transmitted intensity. Variables such as time base and prescaling on the autocorrelator are optimized by the software according to the characteristics of the sample. Safety and verification procedures are described. The trade off in signal-to-noise requirements of both dynamic and classical light scattering are considered in order to enable simultaneous dynamic and classical intensity measurements. An example of the utility of the instrument for studying critical phenomena is given.