Chemical Power Variability among Microscopic Robots in Blood Vessels

TL;DR

This paper analyzes how microscopic robots powered by fuel cells impact oxygen levels in blood vessels, highlighting the effects of circulation path variations and proposing mitigation strategies for oxygen depletion.

Contribution

It evaluates the influence of blood circulation variations on oxygen consumption by microscopic robots and suggests methods to mitigate oxygen depletion in different circulation scenarios.

Findings

Tens of billions of robots can operate with minimal oxygen reduction.

A trillion robots can cause significant oxygen depletion in some body regions.

Active mitigation strategies like oxygen storage can reduce depletion effects.

Abstract

Fuel cells using oxygen and glucose could power microscopic robots operating in blood vessels. Swarms of such robots can significantly reduce oxygen concentration, depending on the time between successive transits of the lung, hematocrit variation in vessels and tissue oxygen consumption. These factors differ among circulation paths through the body. This paper evaluates how these variations affect the minimum oxygen concentration due to robot consumption and where it occurs: mainly in moderate-sized veins toward the end of long paths prior to their merging with veins from shorter paths. This shows that tens of billions of robots can obtain hundreds of picowatts throughout the body with minor reduction in total oxygen. However, a trillion robots significantly deplete oxygen in some parts of the body. By storing oxygen or limiting their consumption in long circulation paths, robots can actively mitigate this depletion. The variation in behavior is illustrated in three cases: the portal system which involves passage through two capillary networks, the spleen whose slits significantly slow some of the flow, and large tissue consumption in coronary circulation.