Rotibots: Cyborgs made of microfauna and microbeads
As increasing volumes of potentially toxic chemicals are shipped globally and incorporated into industrial networks, the risk of chemical spills resulting in environmental degradation is swelling. Whereas traditional organic substances are digestible from an environment by local microbial populations, inorganic and recently developed chemical waste cannot be degraded in these traditional ecological manners. Ecosystems have not been sufficiently exposed to these toxic chemicals to establish metabolic pathways capable of digesting them.
Environmental remediation is required to rehabilitate contaminated ecosystems. Biocatalytic degradation is the process of breaking down molecules into less harmful components. This is a well-regarded potential solution to environmental contamination, which enables scientists to capitalize on preexistent metabolic pathways in microbes. When these pathways are not present, remediative scientists must develop synthetic strategies for cleaning.
Microbeads are one solution to this. By engineering specific microbead structures, scientists have been able to develop high-affinity degradative pathways which can be applied to an expanding range of pollutants. These microbeads exhibit potent remediative potential, however they are limited by their immotility. While we may be able to engineer individual chemicals at the molecular level, engineering directed and dynamic robots capable of seeking and digesting contaminants is a magnitude greater challenge.
The microfauna present within contaminable environments are a possible resolution to this static issue. Motile within the present mediums, these organisms have been selected for rapid dispersal, enabling them to locate nutrients. Microfauna are physically well equipped to navigate ecosystems, however they lack the metabolic pathways to enable digestion of pollutants.
One of the major phyla of such microfauna is Rotifera, commonly termed ‘wheel animals’ or ‘rotifers’. These are a diverse group of microfauna with member species present in a highly diverse range of habitats, though they’re most prolifically found in freshwater. Rotifers are motile and often use cilia to initiate flow streamlines, which enable filter feeding alongside locomotion.
A new development in the field of biohybrid microrobots has combined the cleaning capacity of functionalized microbeads with the propulsion capacity of marine rotifers. The resultant unit is referred to as a ‘rotibot’, and experiments have demonstrated its capacity to effectively clean in aqueous environments.
Due to the negative charge exhibited by rotifer cilia, positively charged microbeads adhere to the cilia, and eventually settle beneath the inner lips of each rotifer mouth. The rotifer cilia beat, producing a micropump effect, thereby promoting fluid flow to locomote the rotifer. This beating simultaneously mixes the aqueous solution around the rotifer to precipitate effective feeding. Once microbeads are in place, any contaminants that the rotifer mouth encounters are degraded.
Rotibots are slightly slower than their rotifer counterparts, however they are still capable of swimming in upstream directions against the current. Rotibots are also able to function in a wide range of aqueous environments. They are able tao vastly increase the decontamination rates of aqueous solution by mass, due to their engaging in active remediation. Depending on the microbeads attached, rotibots have a range of potential functions.
Initial application of rotibot technology was experimentally demonstrated in antibacterial settings. Rotibots were able to inhibit bacteria more than 800% more effectively than passively remediative free microbeads were. The same increase in efficacy was demonstrated when microbeads were used in order to demonstrate rotibot efficacy at degradation of organophosphorus pesticides,. The final experimental conditions tested rotibots’ capacity to degrade heavy metals via chelation, which further galvanized support for rotibot technology, and the widespread applicability this technique may have.
The augmentation of microbead remediative technology with locomotive hosts is indicative of an ongoing trend in the field of microrobotics. Researchers are increasingly aware of the benefits construed by incorporating evolutionarily established biotechnology with contemporary synthetic techniques. The application of this interdisciplinary approach to environmentally remediative practices is all the more timely considering the ongoing issues surrounding contamination of environments.
Rotibot: Use of Rotifers as Self‐Propelling Biohybrid Microcleaners Fernando Soto Miguel Angel Lopez‐Ramirez Itthipon Jeerapan Berta Esteban‐Fernandez de Avila Rupesh Kumar Mishra Xiaolong Lu Ingrid Chai Chuanrui Chen Daniel Kupor Amir Nourhani Joseph Wang First published: 28 March 2019