3D‐printing represents an emerging technology that can revolutionize the way object and functional devices are fabricated. Here the use of metal 3D printing is demonstrated to fabricate bespoke ...electrochemical stainless steel electrodes that can be used as platform for different electrochemical applications ranging from electrochemical capacitors, oxygen evolution catalyst, and pH sensor by means of an effective and controlled deposition of IrO2 films. The electrodes have been characterized by scanning electrode microscopy and energy dispersive X‐ray spectroscopy before the electrochemical testing. Excellent pseudocapacitive as well as catalytic properties have been achieved with these 3D printed steel‐IrO2 electrodes in alkaline solutions. These electrodes also demonstrate Nernstian behavior as pH sensor. This work represents a breakthrough in on‐site prototyping and fabrication of highly tailored electrochemical devices with complex 3D shapes which facilitate specific functions and properties.
On‐site design and fabrication of metal electrodes for different electrochemical applications is possible, thanks to metal 3D printing. Helical‐shaped steel electrodes—fabricated through a selective laser melting technology—are electrochemically modified with IrO2 films and used as capacitors, pH sensors, and catalysts for oxygen evolution reaction, demonstrating excellent performance.
Closing the resource loop by transforming plastic waste into higher value products is an important step for changing from a linear to circular economy. Using a sequential pyrolysis and catalytic ...chemical vapour deposition process, plastics have been successfully converted into carbon nanotubes (CNTs). Pure low density polyethylene (LDPE), polypropylene (PP) and mixed plastics (MP) were used as raw materials in the two-stage process. In the first stage, the plastics were pyrolysed at 600 °C. In the second stage, the non-condensable gases were converted into multi-walled CNTs over a Ni-based catalyst at two different temperatures, 500 and 800 °C. The influence of plastic feedstock and synthesis temperature on the performance of plastic-derived CNTs as electrode materials in electrocatalysis was investigated. The CNTs were evaluated as electrode materials for their heterogeneous electron transfer rate using a redox probe, which showed improved electrochemical behaviour. For oxygen reduction reaction (ORR), CNTs produced at 500 °C demonstrated superior performance compared to those produced at 800 °C. Influence of feedstock on electrocatalytic ORR activity of the as synthesised CNTs was marginal. Temperature was the governing factor influencing the properties of CNTs due to annealing and oxidation of edge defects generated during synthesis at higher temperatures.
•Plastics were converted to carbon nanotubes (CNTs) and used as electrode material.•Electrocatalytic oxygen reduction was observed using plastic derived CNTs electrodes.•CNTs synthesised at 500 °C performed better than those synthetized at 800 °C.•Higher defect density and lower amount of oxidised sites enhanced electrocatalysis.
The availability of drinking water is of utmost importance for the world population. Anthropogenic pollutants of water, such as heavy‐metal ions, are major problems in water contamination. The ...toxicity assays used range from cell assays to animal tests. Herein, we replace biological toxicity assays, which use higher organisms, with artificial inorganic self‐propelled microtubular robots. The viability and activity of these robots are negatively influenced by heavy metals, such as Pb2+, in a similar manner to that of live fish models. This allows the establishment of a lethal dose (LD50) of heavy metal for artificial inorganic microfish robots. The self‐propelled microfish robots show specific response to Pb2+ compared to other heavy metals, such as Cd2+, and can be used for selective determination of Pb2+ in water. It is a first step towards replacing the biological toxicity assays with biomimetic inorganic autonomous robotic systems.
How much is the fish? Artificial inorganic self‐propelled microtubular robots have been used to replace heavy‐metal biological toxicity assays, which use higher organisms. The viability and activity of these robots are negatively influenced by heavy metals, such as Pb2+, in a similar manner to that of live fish models. It is a first step towards replacing the biological toxicity assays with biomimetic inorganic autonomous robotic systems (see figure).
The advancement of additive manufacturing (AM) for metal matrix nanocomposites (MMNCs) is gaining enormous attention due to their potential improvement of physical and mechanical performance. When ...using nanostructured additives as reinforcements in 3D printed metal composites and with the aid of selective laser melting (SLM), the mechanical properties of the composites can be tailored. The nanostructured additive AEROSIL
fumed silica is both cost-effective and beneficial in the production of MMNCs using SLM. In this study, both hydrophobic and hydrophilic fumed silicas were shown to successfully achieve homogenous blends with commercial 316L stainless steel powder. The powder blends, which exhibited better flow, were then used to fabricate samples using SLM. The samples' microstructure demonstrated that smaller grains were present in the composites, resulting in improvements in mechanical properties by grain refinement compared to those of 316L stainless steel samples.
Graphene oxide (GO), an up‐and‐coming material rich in oxygenated groups, shows much promise in pollution management. GO is synthesised using several synthetic routes, and the adsorption behaviour of ...GO is investigated to establish its ability to remove the heavy‐metal pollutants of lead and cadmium ions. The GO is synthesised by Hummers’ (HU), Hofmann’s (HO) and Staudenmaier’s (ST) methodologies. Characterisation of GO is performed before and after adsorption experiments to investigate the structure–function relationship by using Fourier‐transform infrared spectroscopy and X‐ray photoelectron spectroscopy. Scanning electron microscopy coupled with elemental detection spectroscopy is used to investigate morphological changes and heavy‐metal content in the adsorbed GO. The filtrate, collected after adsorption, is analysed by inductively coupled plasma mass spectrometry, through which the efficiency and adsorption capacity of each GO for heavy‐metal‐ion removal is obtained. Spectroscopic analysis and characterisation reveal that the three types of GO have different compositions of oxygenated carbon functionalities. The trend in the affinity towards both PbII and CdII is HU GO>HO GO>ST GO. A direct correlation between the number of carboxyl groups present and the amount of heavy‐metal ions adsorbed is established. The highest efficiency and highest adsorption capacity of heavy‐metal ions is achieved with HU, in which the relative abundance of carboxyl groups is highest. The embedded systematic study reveals that carboxyl groups are the principal functionality responsible for heavy‐metal‐ion removal in GO. The choice of synthesis methodology for GO has a profound influence on heavy‐metal‐ion adsorption. A further enrichment of the carboxyl groups in GO will serve to enhance the role of GO as an adsorbent for environmental clean‐up.
Heavy metals GO! Preparation methodology has a profound influence on the adsorption capacity of graphene oxide (GO) towards heavy‐metal ions. Hummers' (HU) GO shows superior adsorption capability compared to GO prepared by Hofmann's (HO) and Staudenmaier's (ST) methods; this is in direct correlation with the number of carboxylate functionalities present.
Nano/Microrobots Meet Electrochemistry Moo, James Guo Sheng; Mayorga‐Martinez, Carmen C.; Wang, Hong ...
Advanced functional materials,
March 24, 2017, Volume:
27, Issue:
12
Journal Article
Peer reviewed
Artificial autonomous self‐propelled nano and microrobots are an important part of contemporary technology. They are typically self‐powered, taking chemical energy from their environment and ...converting it to motion. They can move in complex environments and channels, deliver cargo, perform nanosurgery, act as chemotaxis and perform sense‐and‐act actions. The electrochemistry is closely interwoven within this field. In the case of self‐electrophoretically driven nano/microrobots, electrochemical mechanism has been the basis of power, which translates chemical energy to motion. Electrochemistry is also a major tool for the fabrication of these micro and nanodevices. Electrochemistry and electric fields can be used for the directing of nanorobots and for detection of their positions. Ultimately, nano and microrobots can dramatically improve performances of electrochemical sensors and biosensors, as well as of the energy generating devices. Here, all aspects in the fundamentals and applications of electrochemistry in the realm of nano‐ and microrobots are reviewed.
The nexus between electrochemistry and nano/microrobots is closely interwoven. In this confluence, fabrication, powering, control and applications of these self‐propelled devices are illustrated. Understanding these fundamentals will push new frontiers for the locomotion of nano/microrobots.
Self‐propelled autonomous nano/microswimmers are at the forefront of materials science. These swimmers are expected to operate in highly confined environments, such as between the grains of soil or ...in the capillaries of the human organism. To date, little attention is paid to the problem that in such a confined environment the fuel powering catalytic nano/microswimmers can be exhausted quickly and the space can be polluted with the product of the catalytic reaction. In addition, the motion of the nano/microswimmers may be influenced by the confinement. These issues are addressed here, showing the influence of the size of the capillary and length of the micromotor on the motion and the influence of the depletion of the fuel and excess of the exhaust products. Theoretical modeling is provided as well to bring further insight into the observations. This article shows challenges that these systems face and stimulates research to overcome them.
Confined space alters the swimming behaviors of the self‐propelled microswimmers due to hydrodynamic interactions between boundaries and swimmers, an effect similar to inertial focusing of passive particles in the microfluidic flow.
We report a facile platform for mass production of robust self-propelled tubular microengines. Tissue cells extracted from fruits of banana and apple, Musa acuminata and Malus domestica, are used as ...the support on which a thin platinum film is deposited by means of physical vapor deposition. Upon sonication of the cells/Pt-coated substrate in water, microscrolls of highly uniform sizes are spontaneously formed. Tubular microengines fabricated with the fruit cell assisted method exhibit a fast motion of ∼100 bodylengths per s (∼1 mm s(-1)). An extremely simple and affordable platform for mass production of the micromotors is crucial for the envisioned swarms of thousands and millions of autonomous micromotors performing biomedical and environmental remediation tasks.
The rise of miniaturized artificial self‐powered devices, demonstrating autonomous motion, has brought in new considerations from the environmental perspective. This review addresses the interplay ...between these nano/micro/macromotors and the environment, recent advances, and their applications in pollution management. Such self‐propelled devices are able to actuate chemical energy into mechanical motion in situ, adding another powerful dimension towards solving environmental problems. Use of synthetic nano/micro/macromotors has demonstrated potential in environmental remediation, both in pollutant removal and contaminant degradation, owing to motion‐induced mixing. At the same time, the chemical environment exerts influence on the locomotion of the motors. These sensitized self‐powered devices demonstrate capabilities for being deployed as sensors and their chemotactic behaviors show efficacy to act as first responders towards a chemical leakage. Thus, the notion of a self‐propelling entity also entails further investigation into its inherent toxicity and possible implications as a pollutant. Future challenges and outlook of the use of these miniaturized devices are discussed, with specific regard to the fields of environmental remediation and monitoring, as we move towards their wider acceptance. We believe that these tiny machines will stand up to the task as solutions for environmental sustainability in the 21st century.
First response: Use of synthetic nano/micro/macromotors has demonstrated potential in environmental remediation, both in pollutant removal and contaminant degradation, owing to motion‐ induced mixing. At the same time, the chemical environment exerts influence on the locomotion of the motors, allowing these sensitized self‐powered devices to be deployed as sensors and first responders to chemical leakage.
Manipulation of a micromotor's locomotion has been the ultimate aim of scientists and engineers alike. While numerous roadmaps have been cast, the interswitching of the locomotion and directionality ...of these miniaturized machines remains elusive. In this report, ultrasound is utilized to produce stop/go motion on bubble‐propelled micromotors via Bjerknes forces. An intricate study using high‐speed camera on the interactions between the bubbles and micromotor is undertaken. The reciprocal action between oscillating bubbles aggregates and ejected microbubbles in an acoustic field demonstrate influence on the motion of the micromotor. Long‐range translational motion can be induced into the micromotor, when repulsive forces between bubble aggregates and ejected microbubbles are manifested in an acoustic field by Bjerknes forces. Additionally, such ultrasonic pulses demonstrate capability to change the directionality of the micromotor, where chirality of the locomotion can be switched. Here, introduction of pulses of ultrasonic irradiation demonstrates new capabilities to switch the motion of bubble‐propelled micromotors.
Under ultrasound irradiation, the vibration of bubbles in solution results in the manifestation of Bjerknes forces in an acoustic field. Such forces allow for the occurrences of both repulsive and attractive forces, being dependent on the bubble sizes. This paves the way for the manipulation of bubble‐propelled micromotors, where stop‐go, translational, and chiral‐directional motion can be induced.
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