The scientific and medical research communities have been looking to develop robots that measure in the nanometer range (that’s one-billionth of a meter) for quite some time. Being so small, they would be able to perform difficult tasks, such as targeted drug delivery to specific cells, or the elimination of harmful antigens, pathogens or viruses. However, the development of such machines raises numerous challenges.
For one, making them small enough to fit between cells remains tricky, and these tiny bots would also need a propulsion system that will allow them to navigate their way through the human body. But now, in a paper published in the June 2014 issue of ACS Nano, an Israeli and German team announced the creation of the smallest nanobot yet, a magnet-guided corkscrew which is propelled by a tiny helical propeller.
The team is comprised of researchers from the Technion-Israel Institute of Technology, the Max Planck Institute for Intelligent Systems, and the Institute for Physical Chemistry at the University of Stuttgart, Germany. Led by Dr. Peer Fischer at the Max Planck Institute, the research team created the tiny helical nanopropeller from a filament of silica and nickel that measures just 70 nanometers in diameter and 400 in length.
That’s more than 1,000 times smaller than the width of a human hair, or 100 times smaller than a single red blood cell, making the wee machine the tiniest nanopropeller humanity has ever created. Instead of carrying its own motor, the propeller is powered by an externally-applied weak rotating magnetic field which causes the prop to spin, driving it and its attached payload forward.
In order to test it, the scientist placed it in a hyaluronan gel, which is similar in consistency to bodily fluids. Like those fluids, the gel contains a mesh of entangled long polymer protein chains. In previous studies, larger micrometer-sized propellers got caught in these chains, slowing or completely halting their progress. The new nanoprop, however, was able to move relatively quickly by simply passing through the gaps in the mesh.
The study’s co-author, Associate Professor Alex Leshanksy of the Technion Faculty of Chemical Engineering, said that the nanobots:
actually display significantly enhanced propulsion velocities, exceeding the highest speeds measured in glycerin as compared with micro-propellers, which show very low or negligible propulsion.
The applications for this device certainly include targeted drug delivery, where the nanobots would be equipped with insulin, antibiotics, or even chemotherapy drugs which they could then deliver to specific cells in the body to speed up the delivery process and reduce side-effects. Scientists could also attach “active molecules” to the tips of the propellers, or use the propellers to deliver tiny doses of radiation.
The applications seem wide, varied, and exciting, from combating diabetes to fighting cancer and HIV with surgical precision. And developments like these, though they measure in the billionth of meters, they add up to a future where lives are healthier, longer and more prosperous.
Nanotechnology has long been the dream of researchers, scientists and futurists alike, and for obvious reasons. If machinery were small enough so as to be microscopic, or so small that it could only be measured on the atomic level, just about anything would be possible. These include constructing buildings and products from the atomic level up, with would revolutionize manufacturing as we know it.
In addition, microscopic computers, smart cells and materials, and electronics so infinitesimally small that they could be merged with living tissues would all be within our grasp. And it seems that at least once a month, universities, research labs, and even independent skunkworks are unveiling new and exciting steps that are bringing us ever closer to this goal.
Once such breakthrough comes from the University of North Carolina at Chapel Hill, where biomedical scientists and engineers have joined forces to create the “smart sponge”. A spherical object that is microscopic — just 250 micrometers across, and could be made as small as 0.1 micrometers – these new sponges are similar to nanoparticles, in that they are intended to be the next-generation of delivery vehicles for medication.
Each sponge is mainly composed of a polymer called chitosan, something which is not naturally occurring, but can be produced easily from the chitin in crustacean shells. The long polysaccharide chains of chitosan form a matrix in which tiny porous nanocapsules are embedded, and which can be designed to respond to the presence of some external compound – be it an enzyme, blood sugar, or a chemical trigger.
So far, the researchers tested the smart sponges with insulin, so the nanocapsules in this case contained glucose oxidase. As the level of glucose in a diabetic patient’s blood increases, it would trigger the nanocapsules in the smart sponge begin releasing hydrogen ions which impart a positive charge to the chitosan strands. This in turn causes them to spread apart and begin to slowly release insulin into the blood.
The process is also self-limiting: as glucose levels in the blood come down after the release of insulin, the nanocapsules deactivate and the positive charge dissipates. Without all those hydrogen ions in the way, the chitosan can come back together to keep the remaining insulin inside. The chitosan is eventually degraded and absorbed by the body, so there are no long-term health effects.
One the chief benefits of this kind of system, much like with nanoparticles, is that it delivers medication when its needed, to where its needed, and in amounts that are appropriate to the patient’s needs. So far, the team has had success treating diabetes in rats, but plans to expand their treatment to treating humans, and branching out to treat other types of disease.
Cancer is a prime candidate, and the University team believes it can be treated without an activation system of any kind. Tumors are naturally highly acidic environments, which means a lot of free hydrogen ions. And since that’s what the diabetic smart sponge produces as a trigger anyway, it can be filled with small amounts of chemotherapy drugs that would automatically be released in areas with cancer cells.
Another exciting breakthrough comes from University of California at Berkeley, where medical researchers are working towards tiny, implantable sensors . As all medical researchers know, the key to understanding and treating neurological problems is to gather real-time and in-depth information on the subject’s brain. Unfortunately, things like MRIs and positron emission tomography (PET) aren’t exactly portable and are expensive to run.
Implantable devices are fast becoming a solution to this problem, offering real-time data that comes directly from the source and can be accessed wirelessly at any time. So far, this has taken the form of temporary medical tattoos or tiny sensors which are intended to be implanted in the bloodstreams. However, what the researchers at UofC are proposing something much more radical.
In a recent research paper, they proposed a design for a new kind of implantable sensor – an intelligent dust that can infiltrate the brain, record data, and communicate with the outside world. The preliminary design was undertaken by Berkeley’s Dongjin Seo and colleagues, who described a network of tiny sensors – each package being no more than 100 micrometers – in diameter. Hence the term they used: “neural dust”.
The smart particles would all contain a very small CMOS sensor capable of measuring electrical activity in nearby neurons. The researchers also envision a system where each particle is powered by a piezoelectric material rather than tiny batteries. The particles would communicate data to an external device via ultrasound waves, and the entire package would also be coated in a polymer, thus making it bio-neutral.
But of course, the dust would need to be complimented by some other implantable devices. These would likely include a larger subdural transceiver that would send the ultrasound waves to the dust and pick up the return signal. The internal transceiver would also be wirelessly connected to an external device on the scalp that contains data processing hardware, a long range transmitter, storage, and a battery.
The benefits of this kind of system are again obvious. In addition to acting like an MRI running in your brain all the time, it would allow for real-time monitoring of neurological activity for the purposes of research and medical monitoring. The researchers also see this technology as a way to enable brain-machine interfaces, something which would go far beyond current methods. Who knows? It might even enable a form of machine-based telepathy in time.
Sounds like science fiction, and it still is. Many issues need to be worked out before something of this nature would be possible or commercially available. For one, more powerful antennae would need to be designed on the microscopic scale in order for the smart dust particles to be able to send and receive ultrasound waves.
Increasing the efficiency of transceivers and piezoelectric materials will also be a necessity to provide the dust with power, otherwise they could cause a build-up of excess heat in the user’s neurons, with dire effects! But most importantly of all, researchers need to find a safe and effective way to deliver the tiny sensors to the brain.
And last, but certainly not least, nanotechnology might be offering improvements in the field of prosthetics as well. In recent years, scientists have made enormous breakthroughs in the field of robotic and bionic limbs, restoring ambulatory mobility to accident victims, the disabled, and combat veterans. But even more impressive are the current efforts to restore sensation as well.
One method, which is being explored by the Technion-Israel Institute of Technology in Israel, involves incorporating gold nanoparticles and a substrate made of polyethylene terephthalate (PET) – the plastic used in bottles of soft drinks. Between these two materials, they were able to make an ultra-sensitive film that would be capable of transmitting electrical signals to the user, simulating the sensation of touch.
Basically, the gold-polyester nanomaterial experiences changes in conductivity as it is bent, providing an extremely sensitive measure of physical force. Tests conducted on the material showed that it was able to sense pressures ranging from tens of milligrams to tens of grams, which is ten times more sensitive than any sensors being build today.
Even better, the film maintained its sensory resolution after many “bending cycles”, meaning it showed consistent results and would give users a long term of use. Unlike many useful materials that can only really be used under laboratory conditions, this film can operate at very low voltages, meaning that it could be manufactured cheaply and actually be useful in real-world situations.
In their research paper, lead researcher Hossam Haick described the sensors as “flowers, where the center of the flower is the gold or metal nanoparticle and the petals are the monolayer of organic ligands that generally protect it.” The paper also states that in addition to providing pressure information (touch), the sensors in their prototype were also able to sense temperature and humidity.
But of course, a great deal of calibration of the technology is still needed, so that each user’s brain is able to interpret the electronic signals being received from the artificial skin correctly. But this is standard procedure with next-generation prosthetic devices, ones which rely on two-way electronic signals to provide control signals and feedback.
And these are just some examples of how nanotechnology is seeking to improve and enhance our world. When it comes to sensory and mobility, it offers solutions to not only remedy health problems or limitations, but also to enhance natural abilities. But the long-term possibilities go beyond this by many orders of magnitude.
As a cornerstone to the post-singularity world being envisioned by futurists, nanotech offers solutions to everything from health and manufacturing to space exploration and clinical immortality. And as part of an ongoing trend in miniaturization, it presents the possibility of building devices and products that are even tinier and more sophisticated than we can currently imagine.
It’s always interesting how science works by scale, isn’t it? In addition to dreaming large – looking to build structures that are bigger, taller, and more elaborate – we are also looking inward, hoping to grab matter at its most basic level. In this way, we will not only be able to plant our feet anywhere in the universe, but manipulate it on the tiniest of levels.
As always, the future is a paradox, filling people with both awe and fear at the same time.