Surface-induced flow A natural microscopic engine using infrared energy as fuel

Although this experimental setup is not using biological samples, the observed effect, that is, an intratubular flow that occurs in the absence of any pressure gradient and that it is a consequence of Exclusion Zone formation in water inside those tubes may be also valid to biological tubes as capillaries and the blood flow, infrared light is the unique energy source necessary to achieve this, other wavelengths of light also can expand Exclusion Zone waters:

" Since incident radiant energy (light) fuels EZ expansion, that energy may likewise fuel the self-driven flow. We confirmed that application of ultraviolet-containing white light could boost flow velocity by up to 500% (5). Thus, the self-driven flow mechanism can convert radiant energy into kinetic energy." {Credits 1}

But IR light is more effective and ubiquitous:

" The practical significance of IR utilization lies in its ubiquity. For biological entities in particular, IR can be both exogenous and endogenous. Approximately 50% of solar energy received by earth is in the form of IR (25); metabolic activities of living organisms generate thermal radiation (heat), which is essentially IR (26)." {Credits 1}

So:

" Regarding the self-driven flow mechanism, blood vessel interiors appear to be lined with EZs. The glycocalyx, a gel-like polysaccharide, lines the insides of vessels (21, 22). Beyond the glycocalyx exists a cell-free layer that excludes red blood cells (23). The exclusion of red blood cells from an annular region inside the vessels implies the presence of an EZ, a seemingly critical feature for the existence of SIF. If SIF exists in the circulatory system, then we can make two predictions: (i) IR can be an energy source for blood circulation, and (ii) flow should persist even in the absence of cardiac contraction." {Credits 1}

{Credits 1} 🎪 Li, Z., & Pollack, G. H. (2020). Surface-induced flow: A natural microscopic engine using infrared energy as fuel. Science Advances, 6(19), eaba0941. © 2020 The Authors. Content from this work may be used under the terms of the Creative Commons Attribution NonCommercial License.