A Self-Build Apparatus for Oscillatory Flow Birefringence Measurements in a Co-Cylindrical Geometry

Abstract

We developed a high-sensitive apparatus for oscillatory flow birefringence measurement in a co-cylindrical geometry. The apparatus was comprised of a conventional rheometer, an Argon ion laser, and a lock-in amplifier. The laser was irradiated to samples under sinusoidal strains, and transmitted light intensities were analyzed using the lock-in amplifier to evaluate flow birefringence. TTL signals, which were transformed from sinusoidal strains using a comparator, were used as reference signals for lock-on detection at low frequencies. First, phase shifts between the true strain and TTL reference signal generated by the comparator were calibrated. Next, reliability of the apparatus was assessed using a wormlike micellar solution, whose flow birefringence behavior are well known. Finally, sensitivity of the birefringence measurement was checked using a low birefringent cellulose nanofiber (CNF) dispersion. Flow birefringence behavior of the CNF dispersion became measurable thanks to a long optical pass length of the geometry. The apparatus will be a strong tool to reveal dynamics of low birefringent solutions.

Rheo-Optical Study on the Viscoelastic Relaxation Modes of a Microgel Particle Suspension around the Liquid–Solid Transition Regime

“…Strain-induced birefringence measurements were conducted using a homemade Rheosol-G3000 shear birefringence apparatus for 1 kg m –3 ≤ c < 10 kg m –3 and using the homemade shear dynamic birefringence apparatus for 10 kg m –3 ≤ c < 40 kg m –3 . The details of these apparatuses have been reported elsewhere. ,, The complex strain-optical coefficient, K *­(ω)  K ′(ω) + i K ″(ω), was calculated as a complex ratio of the oscillatory birefringence to the sinusoidal strain just like the complex modulus, G *, which is a complex ratio of the stress to the strain, as a function of angular frequencies ω ranging between 100 and 0.1 rad s –1 . The oscillatory strain amplitude was kept at γ 0 = 0.01 to ensure the linear viscoelastic regime.…”

“…The details of these apparatuses have been reported elsewhere. 24,34,35 The complex strain-optical coefficient, K*(ω)  K′(ω) + iK″(ω), was calculated as a complex ratio of the oscillatory birefringence to the sinusoidal strain just like the complex modulus, G*, which is a complex ratio of the stress to the strain, 32 as a function of angular frequencies ω ranging between 100 and 0.1 rad s −1 . The oscillatory strain amplitude was kept at γ 0 = 0.01 to ensure the linear viscoelastic regime.…”

Experimental Studies of Flow-Induced Birefringence in Complex Fluids

“…Some types of wormlike micellar solutions have attracted research attention because they generate shear-induced and shear-banding structures [4][5][6][7][8][9][10] . As already mentioned, traditional FIB measurements such as the crossed-Nicol method have some limitations.…”

“…Kádár et al 14) reported birefringence patterns as being sensitive to flow-induced structural changes, thus FIB measurement is considered to be an essential tool for examining the flow-induced structure of CNC suspensions. Tanaka et al 10) developed a highly sensitive apparatus for oscillatory FIB measurement and succeeded in measuring a low-bire-fringent suspension of cellulose nanofibers.…”

Birefringent Properties of Aqueous Cellulose Nanocrystal Suspensions

“…Flow birefringence has been used to study the birefringence relaxation of CNCs (Tanaka et al 2019). The complex strain-optical coe cient was measured experimentally using a custom-built apparatus for oscillatory ow birefringence measurements (Tanaka et al 2018) and was compared to theoretical values, for which the CNCs dimensions were measured by transmission electron microscopy.…”