Meeting Abstract
Hemolymph in insects plays a vital role in processes that range in scale from macroscopic – such as primary wound healing – to microscopic – such as flowing through vessels to deliver nutrients – to nanoscopic – such as fending off bacteria and viruses. When studying insect biomechanics, it is therefore crucial to understand the rheological properties of hemolymph at different scales. From a rheological perspective, hemolymph is a suspension of adherent and non-adherent micron-sized hemocytes suspended in plasma. Even though at the macro-scale the suspension may behave as a single-phase liquid, it has been a long-standing challenge to measure its rheological properties at the micro- and nano-scales, where the effects of hemocytes can be significant. Here, we present the findings of a multi-scale rheological study of hemolymph using a combination of traditional and novel characterization techniques. To probe the macroscopic properties of hemolymph, we used a commercial cone-and-plate rheometer (Brookfield Engineering DV-II+ Pro) with temperature controlled using a circulating bath (model Lauda RE206. To probe the micro- and nano-rheology, we suspended magnetic micro- and nano-wires, respectively, in a droplet of hemolymph in a controlled inert atmosphere and performed magnetic rotational spectroscopy by rotating the probe with a rotating magnetic field. For both methods, we conducted trials in atmospheres of nitrogen (~99%) to prevent or lessen the effects of clotting induced by oxygen. Our findings show that as scale is reduced, the effect of hemocytes on rheology of hemolymph becomes increasingly dominant and drastically changes the mechanical response of the hemolymph.
