Innovations and Emerging Applications of Micro- and Nano-bots

Miniaturization, particularly of electronics and sensor technologies, has had a tremendous effect across industries. In the medical imaging and diagnostics space, the concept of smart pills has taken flight in the field of gastrointestinal imaging, though their impact on other application areas has remained muted. Read more in this Frost & Sullivan analysis.

A black-and-white photo doing the rounds of the internet for some time now, taken circa 1960, shows a couple of dockworkers loading a refrigerator-sized something onto a truck. Upon closer examination, one can spot IBM written on it, and the accompanying text explains that it is a 5 megabyte (MB) hard drive. The Apple iPhone X that was launched last week has a 256 gigabyte (GB) hard drive—more than 50,000 times the storage capacity—in an elegant-looking shell that is a fraction of the size of IBM’s monstrous contraption.

Miniaturization, particularly of electronics and sensor technologies, has had a tremendous effect across industries. In the medical imaging and diagnostics space, the concept of smart pills—ingestible sensors that are modeled after pharmaceutical pills but designed for advanced monitoring, diagnostic, therapeutic and/or surgical purposes—emerged in the mid-2000s. While smart pills have taken flight in the field of gastrointestinal imaging (in the form of wireless capsule endoscopes), their impact on other application areas has remained muted.

Smart Pills or Miniature Swiss Army Knives

A long-established visual imagery of a medical microbot (short for microscopic robot, typically less than 1 millimeter in length) is that of a miniaturized submersible swimming inside the body, equipped with tools for tissue biopsies, suturing and ablation. This is an ambitious concept, but the achievements so far do not match this expectation.

However, several research groups and companies are trying to make this a reality: prototypes have been showcased at scientific conferences and have been discussed in science journals. The stress on “science” is to establish that these have not been commercialized yet. Innovators include:

Microbot Medical (Hingham, Mass.)

The company has developed a concept technology platform that is a miniscule autonomous “crawling” robot. Company-released images of the ViRob platform show a tick-like device that is slightly larger than a grain of rice. Microbot Medical envisions that this robot will be able to crawl into tight spaces, such as blood vessels, dental cavities, the digestive tract and the respiratory system. ViRob can be controlled remotely using electromagnetic fields. The company said ViRob will be a component of new products that it is developing to serve as shunts to drain fluid accumulation in the spinal cord and the brain.

Multi-Scale Robotics Lab (MSRL), ETH Zurich (Zurich, Switzerland)

MSRL researchers are pursuing multi-disciplinary studies to develop robotic systems of various scales and for myriad applications. An important focus area is the development of micro- and nano-scale robots for surgical procedures. The team has demonstrated the use of a micron-sized metallic pellet in ophthalmic surgeries in animals. A 285 micron-diameter pellet (about four times the width of a strand of hair) was injected by needle into the eye of a pig. The pellet was controlled and moved around along three axes using an external electromagnetic field called OctoMag. The team published findings that cite the device’s reliable navigation in other animal subjects, stating that the microbot shows potential for suture-less surgeries.

Department of Nanoengineering, UC San Diego (La Jolla, Calif.)

A team of researchers has developed what it calls picayune robots—micro-motor-powered tubular structures that measure 20 microns in length and 5 microns in diameter. These zinc-based robots were injected into a live mouse with the aim of delivering drugs to a target organ. The researchers used an imaginative propelling mechanism: the zinc tubes, when in contact with the hydrochloric acid present in the digestive juices in the stomach, generate hydrogen bubbles. As these bubbles pop, they propel the robot forward.

The findings of this study were published in the journal ACS Nano; the study claims that the robot traveled at a speed of 60 microns per second, which is considerable for the scale of operation. The robots were ingested orally; upon reaching the stomach, they appear to have raced forward, embedding themselves onto the inner lining of the stomach, where they deployed their drug load.

California Institute of Technology (Pasadena, Calif.)

Fabrication at the nano-scale is understandably complex. Not only is visualization difficult, but successful miniaturization and assembly of components is a tall order. Here is where the idea of nucleic acid robots or nubots can be useful. Unlike the prototypes described above, these are not electromechanical devices, but organic molecules that can be used to activate small molecules. These nucleic acid fragments, in effect, act as robotic agents, navigating and performing as directed. Nubots are believed to be best suited to deliver drugs to target regions.

Lulu Qian, professor at the California Institute of Technology, has developed a DNA robot that can transport drug cargo. Qian’s group loaded a short fragment of single-stranded DNA with a fluorescent-tagged biomolecule. Under microscopic observation, the strand appeared to “carry” the load with its “hands” while it “walked” on the track provided by a double-stranded DNA. In other words, the drug cargo experiences a strong covalent bond with the nubot, firmly attaching itself to the nubot’s hands. The other end of the nubot forms momentary bonds that form and break, propelling it forward. Once it reaches the target, a stronger bond is made between the target and the cargo, at which point the cargo is transferred.

The Road Ahead

In a report on smart pills published in 2013, Frost & Sullivan opined: “It can be fathomed that in the coming years, micro- and nano-robots would be performing surgeries on the inside, with surgeons controlling them from the outside.” Four years later, despite strides being made, there has been no tangible output from the research community.

However, as with surgical and industrial robots that experienced significant development time and several failed prototypes, microbots are also undergoing a grueling development phase. Indeed, it is common and maybe even necessary for cutting-edge technologies to undergo developmental delays. As Victor Hugo said, “No force on Earth can stop an idea whose time has come.” Frost & Sullivan believes that micro- and nanobots are such compelling ideas.

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