Micro squeeze flow rheometer for high frequency analysis of nano-litre volumes of viscoelastic fluid

In this paper, the design, fabrication and experimental analysis of a piezoelectrically actuated micro squeeze flow rheometer is presented. Being only 30x30x0.5 mm in size, the micro rheometer is sensitive to very small volumes of the order of 1-10 nano-litre of liquid and light enough to operate at frequencies in the kHz regime, an order of magnitude higher than normally attainable with conventional cone and plate rheometry. Initial experiments show that the response of the rheometer is dependent on the viscoelasticity of the fluid being tested. The prototype was used to measure the moduli of poly(dimethylsiloxane) (PDMS) of viscosity 10 Pa s, a nonvolatile viscoelastic fluid, over the frequency range of 10-1000 Hz. Results show good agreement between with the moduli measured using conventional rheometry up to 100 Hz and with values extrapolated up to 1 kHz.