Abstract
Optimal tip sonication settings, namely tip position, input power, and
pulse durations, are necessary to ensure proper mixing and maintain
solution temperature below a critical temperature. This is significant
for temperature sensitive procedures like preparation of viable cell
extract for in vitro protein synthesis. In this paper, the
optimum tip immersion depth is estimated which ensures maximum mixing
thereby enhancing thermal dissipation of local cavitation hotspots
inside the sonication tube; from modeled velocity field streamlines this
is found at immersion depths between 20-30% height below the liquid
surface. A simplified finite element (FE) heat transfer model is
presented and validated experimentally with (R2> 97%) which can predict the temperature rise over time in
a tip-sonicated vessel. This model is used to observe the effect of
temperature rise on cell extract performance of E. coli BL21 DE3
star strain and estimate the temperature threshold. From the combined
heat map of yield and temperature it is observed that yield is
correlated with final steady state temperature. Relative yields in the
top 10% are observed for solution temperatures maintained below
32C; this reduces below 50% relative yield at temperatures above
47C. To extend utility of these finite element models to other
temperature sensitive sonication processes, we also present a
generalized workflow for direct simulation using the FE code as well as
master plots for estimation of sonication parameters (power input and
pulse settings) without need of running the code.