Firstly, what is the ideal digital resolution of frames for accurate particle positioning? Literature reports suggest roughly 1024×768, but why?
Secondly, what is the maximum fps of the digital camera to allow the widest application? 500fps showed up in literature in order to track the particles in low viscosity environment, but why 500fps quantitatively?
Possible candidates (around 1024×758@500fps):
Particle tracking microrheology may mean two different methods. One is single particle tracking technique, where the particle acts as a probe to investigate the rheology of the matrix. Another is general particle tracking microrheology where the ensemble of many particles itself is investigated. The particle tracking methods considered here involve the use of optical microscope. DWS which involve laser light scattering is not considered here. In DWS the MSD is not directly tracked but calculated from g2(t)-1.
The detailed principles of optical and video microscopy were reviewed. Thierry Savin’s PhD dissertation (MIT, 2006) is a good source of information.
An inverted microscope with fluorescent, live cell, time-lapse imaging, high-speed multi-fluorescence optical sectioning, polarization contrast and DIC, micromanipulation, etc. is favorable. Oil immersion objectives are required to correctly resolve Brownian colloidal particles.
60X oil immersion type objective lens (Olympus, Japan) with numerical aperture of 1.40, while 500 nm probe particles were observed using 100X oil immersion type objective lens with numerical aperture of 1.42.
Cooling reduces the array’s dark current, improving the sensitivity of the CCD to low light intensities, even for ultraviolet and visible wavelengths. Professional observatories often cool their detectors with liquid nitrogen to reduce the dark current, and therefore the thermal noise, to negligible levels. Magnification is characterized by nm per pixel. Generaly hundreds of nm per pixel can achieved, which yields spatial resolutions of tens of nm, well below the optical resolution of ~250 nm.
How to know which in the current frame is the particle in the last frame?
Calculation of: MSD, PDF
Routines here.
Aim: To aid the theoretical modeling of the rheological data.
Used to calculate zeta-potentials.
Samples: PEG 35k aqueous solutions at cp = 0, 0.063, 0.1, 0.25, 0.4, 0.63, 0.8, 1.0 wt%
Instrument: AR-G2
Procedure: yet to determine.
Samples: Neat Laponite suspension, Laponite/PEG suspension with PEG 35k of cp = 0.063, 0.1, 0.25, 0.4, 0.63, 0.8, 1.0 wt%
Instrument: Malvern Zetasizer nano zs90