Influence of sonication on the release from hydrogel capsules
The objective is to investigate the influence of sonication on the
mechanical and release properties of hydrogel capsules. A new
fabrication process is developed to fabricate millimetric capsules made
of a highly-viscous liquid core protected by a thin hyperelastic
alginate membrane. At high intensities and/or long exposure times,
sonication can lead to the capsule rupture, because it induces fatigue
in the membrane. Below the breakup threshold, no remnant effect of
sonication is, however, measured on the capsule mechanical
properties. The release is studied by sonicating capsules filled with
blue dextran suspended in an aqueous solution. The mass release that
results from sonication is found to be proportional to the sonication
duration time and pressure wave amplitude. A possible physical
interpretation is that the acoustic streaming flow induced by the
ultrasonic wave enhances convection in the vicinity of the capsule
membrane and thus mass release. We have finally quantified the passive
release subsequent to low-intensity sonications:
it is on average identical to the one measured on non-sonicated
capsules. Overall the membrane therefore recovers its physical and
mechanical properties after sonication. If sonication leads to an
increase in porosity of the capsule membrane, the increase is temporary
and reverses back at the end of the ultrasonic stimulation.
Figure 1: Sonication of hydrogel capsules
Collaborators
Liguo Zhang, Stimulation ultrasonore de billes et capsules : mesure des propriétés mécaniques et favorisation du relargage pour vectorisation, PhD Thesis, UTC, February 2012.