Challenges of the movement of catalytic micromotors in blood

Abstract

Catalytic microjet bubble-propelled engines have attracted a large amount of interest for their potential applications in biomedicine, environmental sciences and natural resources discovery. One of the current efforts in this field is focused on the search of biocompatible fuels. However, only a minimal amount of effort has been made to assess the challenges facing the movement of such devices in a real world environment, especially with regards to the components of blood and their interactions with the catalytic microjets. Herein, we will show the limitations on the movement of catalytic microengines prepared via the rolled-up, as well as the templated-electrochemical deposition method, in an artificial blood sample, due to the presence of two main components of animal blood: the cellular component (red blood cells in this study) and serum. We will show that the motion of catalytic microjets is only possible in highly diluted dispersions of the red blood cells and serum. This finding has a profound implication on the development of the whole field, where the components found in real environments have to be considered carefully, and issues arising from the presence of such components have to be resolved prior to deploying these devices in real world applications.

Efficient bubble propulsion of polymer-based microengines in real-life environments

“…12,13,15,16 Overall, these results clearly indicate that although the real sample matrix has a signicant effect on the microengine velocity (with higher speed diminutions upon increasing the complexity of the matrix), polymer-based microtube engines can move efficiently at relatively high speeds in a broad spectrum of uids. We attribute the favorable propulsion of polymer-based microtube engines in diverse raw real samples, compared to the greatly hindered motion reported recently for Cu-Pt microjets, 19,20 to their optimal geometry, well dened shape, large opening and light weight. Such polymer-based micromotors consist of a thin polymeric outer layer and a thin platinum inner layer (100 nm thick for each layer) and have relatively large openings in both sides (over 1.2 mm in the smaller opening), as clearly indicated in the inset SEM image of Fig.…”

“…The impeded movement in such samples has been attributed to high viscosity of these media and to co-existing molecules that passivate the catalytic Pt surface. 19,20 Since bubble-propelled microengines can be prepared by different fabrication methods and using different materials, 1 it is essential to carefully examine this important issue, in connection to other common protocols for fabricating bubble-propelled microtube engines, and to gain understanding of the effect of the motor design and composition on propulsion efficiency in different media.Here, we wish to demonstrate that template-prepared polymer/Pt microtube engines display efficient propulsion even in undiluted seawater and serum matrices, and to examine the effect of various undiluted (and slightly diluted) real-life environments upon their movement. Template electrodeposition has been shown to be particularly attractive for preparing polymer-based catalytic microengines (Fig.…”

“…[12][13][14][15][16][17][18] However, recent reports claimed that the movement of bubble-propelled Cu-Pt microengines is greatly hindered in various diluted real samples, and even completely stopped in highly diluted serum or seawater. 19,20 Such observations may have profound implications on the scope of future applications of microscale machines. The impeded movement in such samples has been attributed to high viscosity of these media and to co-existing molecules that passivate the catalytic Pt surface.…”

“…The impeded movement in such samples has been attributed to high viscosity of these media and to co-existing molecules that passivate the catalytic Pt surface. 19,20 Since bubble-propelled microengines can be prepared by different fabrication methods and using different materials, 1 it is essential to carefully examine this important issue, in connection to other common protocols for fabricating bubble-propelled microtube engines, and to gain understanding of the effect of the motor design and composition on propulsion efficiency in different media.…”

“…These speeds are lower than that observed in deionized water (980 mm s À1 , i.e., 140 body lengths per s). Yet, unlike Cu-Pt microengines that completely stopped their movement even in 50% of serum or 10% seawater samples, 19,20 the polymer-based microengines retain attractive propulsion behavior in undiluted seawater and serum samples, indicating promise for diverse practical environmental and biomedical applications, such as oil remediation, toxicity assessment or target isolation. Note also from the SEM image of Fig.…”