The authors construct a colloidal model system to experimentally measure particle currents through microfluidic channels and analyze the fluctuations in these currents using the power spectral density (PSD). The PSD exhibits two distinct regimes: a low frequency regime with no significant frequency dependence, and a high frequency regime that decays as 1/f^2 with pronounced oscillations.
The authors show that the low frequency regime corresponds to fluctuations in the random arrival of particles into the channel, while the high frequency regime corresponds to fluctuations in the distribution of particle transit times through the channel. By considering a model for shot noise with a finite transit time and incorporating the experimentally measured distribution of particle velocities, the authors are able to quantitatively reproduce the features of the experimental PSD.
The particle velocity distribution is found to sensitively reflect the confining geometry of the channel, with variations in velocity arising from both the Poiseuille flow profile and small fluctuations in the particle height above the channel base. The authors demonstrate how these details of the velocity distribution govern the form of the resulting PSD, establishing concrete links between the PSD and the underlying physical mechanisms in this experimental system.
This work highlights how the high level of control and direct observation possible in colloidal systems can provide insights into the fluctuation behavior of confined transport processes, which are challenging to probe directly in molecular-scale systems like nanopores.
Til et annet språk
fra kildeinnhold
arxiv.org
Viktige innsikter hentet fra
by Stuart F. Kn... klokken arxiv.org 10-03-2024
https://arxiv.org/pdf/2404.17291.pdfDypere Spørsmål