Robotic toys may have topped many of the 2017 Christmas lists for both children and adults, alike, but there is a whole other breed of robots which are far less conspicuous but are magnificent and microscopic – nanorobots.
As industrious and inventive humankind is, it is no surprise that our curiosity into robotics and machinery would eventually delve into the nanoscale. The field is still in its infancy but there are clear opportunities for such development to being revolutionary in fields such as medicine, energy-generation and the removal of pollutants from the environment.
Here we will look at a few of the heroic abilities of these microscopic marvels:
Nanobots can be utilised to ‘herd’ oil spills to prevent them from spreading further and thus allow them to be cleaned up in a swift and easy manner. This is achieved by the “actively moving motors” which can function by gathering up and leaching contaminants such as oil from the water surface to. These nanobots (or microbots) obtain their power by converting chemical energy into mechanical energy by methods such as decomposing hydrogen peroxide into oxygen bubbles.
Research found that a superhydrophobic (very water repellent) compound made up of 12 carbon atoms along with a sulphur atom (n-Dodecanethiol) is the ideal structure to remove oil droplets from the water surface. This compound was used to modify a micromotor.
The advancement of this technology is promising but there are still obstacles to overcome before it could be used within the field. The composition of micromotors which often utilise a concoction of heavy metals such as gold, silver and platinum along with hydrogen peroxide could cause the leaching of unwanted chemicals into the environment, toxicity to organisms and, since the micromotors are self-propelling, the possibility of pollutants being further propagated.
Robots created from DNA have been programmed to perform functions in the same way a computer chip does. Researchers utilised a technique known as DNA origami in which a long strand of DNA is ‘stapled’ by smaller DNA strands to achieve a desired structure. These nanobots have been successfully deployed in living organisms – cockroaches to be precise. Specific proteins within the cockroach act as triggers for the bot to release its ‘payload’ which can then interact with the target cockroach cell.
In the future, this could be used as a diagnostic tool to retrieve biochemical and physiological information from an organism, although to be used in humans, work must be done to improve the capacity and efficiency of the DNA nanobot.
In a fascinating study earlier this year, scientists developed a four-armed microstructure (a “tetrapod”) to be worn by a single sperm cell. Now, this isn’t taking fashion choices a bit too far, but a method to deliver drugs to cells in the cervix and ovaries.
Sperms cells have evolved to be biocompatible within the female reproductive system and, as they are able to self-propel, they are able to move through it freely. The structure of the sperm nucleus gives it a remarkable capacity retain drugs whilst protecting them from “body fluid dilution, immune-reactions and degradation by enzymes”.
Once the sperm-hybrid micromotor has been guided to the correct location with the assistance of an external magnet, the sperm squeezes out from the tetrapod case and “fuses” with the cell membrane thus allowing the drugs to be released in the target cell. The precision enabled by this ingenious technique opens up new pathways in the administration of drugs to affected cells in the treatment of gynaecological cancers and other ailments. Before the microbots can be trialled in humans, further research needs to done to ensure safe biodegradability of the synthetic components.
Research is moving towards one of the ultimate goals of nanorobotics in clinical fields – robots that can be ingested (or perhaps injected or inhaled) and taken into the human body to carry out functions to cure diseases, correct cellular abnormalities and heal ailments. Although the science is a long way off the dream, steps are being taken to bring us closer.
The starting points in this ‘Holy-Grail of Chemistry’ is to develop protein machinery. In order to do this, we need to fully understand the complex compounds which autonomously carry out tasks within the body. These include compounds such as motor proteins in muscle tissue, protein cofactors that are essential in creating the correct protein structures and proteins which are involved in the ‘reading’ (transcription) of DNA which then goes on to translate the DNA into proteins that make up every cell in our bodies.
From this growing comprehension, scientists have been able to engineer synthetic versions of such compounds with additional functionality. Researchers in Japan have recently synthesised proteins which respond to external stimuli such as light or ATP (adenosine triphosphate) with binary feedback (digital encoding/decoding in which there are exactly two possible states) that prompts logic gate functions (an elementary building block for digital circuits).
This step towards controllable protein machinery has real, imminent potential for nanorobotic drug-delivery. The understanding of how this technology could be utilised for wider clinical applications is still in its infancy but the possibilities it could bring are very exciting.
Researchers in Singapore have been able to construct a functioning graphene engine with a thickness of just 1 nanometer. The engine is constructed from a single layer of graphene contaminated with a few chlorine fluoride (ClF3) molecules and it functions in the same manner as a 2-stroke combustion engine. The energy for the engine is supplied by a laser which causes the chlorine fluoride molecules to react and create internal pressure in the graphene membrane. This pressure equals approximately 106 Pa – many times higher than your average car tyre pressure. This creates a high-power volume changeable actuator through the disassociation and chemisorption of chlorine fluoride to the graphene surface. When the laser is turned on and off, the membrane rises and falls in the same manner as an engine piston.
This nano-engine is promising for future applications in nano/ micro robot technology; it has demonstrated impressive endurance lasting over 10,000 cycles with zero degradation to the machine.
A nano-inspired future
It is a mind-boggling prospect that we already have the technology to create such futuristic machines. Although we are many years away from seeing these nanobots playing a role in our daily lives, science is making exciting steps towards reaching those ‘Holy Grails’. There are many obstacles to overcome on this journey, such as the complexities in loading nanobots of such small scale with sufficient programming and efficiency to carry out complex tasks, and the assurance of biocompatibility. However, the benefits could be an astounding advancement in the medical, environmental and wider scientific fields. Watch this space.