Lean, mean micromachine

In a room lined with medical encyclopaedias and flecks of subdued light, Antoine Barbot is struggling to work the machine in front of him. It is emitting a series of whirrs and hisses, potential signs that it might spring to life, but nothing is happening. “This machine is too big, it’s not on my scale,” he says.

A large Nespresso machine is certainly outside of Barbot’s professional orbit. As a research associate at the Hamlyn Centre in Imperial College London, Barbot spends his time working with devices on the scale of 200μm – roughly the length of a human hair.

He has spent the past two years working at the Hamlyn’s EPSRC Micro-Machining Facility, a cuttingedge research wing that has experimented with miniature robotics since it was established in 2014. More specifically, he “has been operating at a submillimetre level”, working to design, manufacture and orient tiny robots to perform a range of minimally invasive medical procedures.

With the help of six 3D printers, the centre has the capacity to create ultra-small fibrebots, tiny devices made of hollow optical fibres equipped with grippers and scalpels that can be as small as 150nm.

At a micro level

Recently, Barbot has been working to develop a more precise manufacturing system at the microlevel, seeking to equip these machines with 2D sensors, enabling them to perform intricate medical tasks and provide feedback to surgeons in real time.

“This work on floating microrobots is one of the first applications where these robots are being designed for surgery,” Barbot says. “Many people are looking at tiny robots that can be injected into the body and deliver drugs at specific locations, but we are focusing on how these robots could work once they are on the inside.”

The first robotically assisted MIS operation was performed by ‘Probot’, a device developed through laboratory studies at Imperial, before being clinically applied to patients for prostate surgery in April 1991. These days, the Da Vinci surgical system is commonly used, helping around 200,000 operations a year, mostly hysterectomies and prostate removals.

While these devices are reliable and widely used, as Bardot says, most of the scalpels, blades and tweezers that currently operate are above or within the 1mm range. Naturally, the same can be said of devices that are installed within the body, such as catheters or implants.

200,000
Operations a year – mostly hysterectomies and prostate removals – use the Da Vinci surgical system.
The Economist

To be more precise, researchers are experimenting with these ultra-small nanobots, seeking to propel them into bodily corners and cavities that either cannot be reached or are too delicate to explore.

“The goal is to improve the surgical techniques so patients can recover faster with less tissue damage,” says Barbot. “But these tools are also allowing us think of new surgeries that were not possible before.”

Problematic obstacles

To become a reality, there are a range of problems to overcome. Usually a strange and complex place to inhabit, the rules, logic and proportion of things at or above the millimetre range are turned on their head. “A classic problem that we get in microrobotics is the need to redesign things and find new solutions to problems that only occur at the micro level,” Bardot says. “We can scale things down… I think the smallest electrical motor might be a millimetre in size. But at some point, if we want to go further, we need new ways of designing and fabricating things.”

Along with bodily rejection, a problem with medical micromachining is equipping robots with adequate sensing capabilities. Despite a range of impressive functions – from running to swimming – most tests have been conducted in laboratory conditions, a far cry from the dark cavernous expanse of the human body.

Given that microbots are too small to be seen by surgical cameras and too fine to house sensors or computers, it remains to be seen how these devices can provide sensory feedback once inside the patient.

“The basic idea revolves around this relationship between sensor and actuator, the actuator to interact with your environment and you need sensors to know what you’re doing,” Bardot explains. “Currently we don’t have any tools at this level.”

To avoid this, Bardot and Imperial researchers have been working to uncover a more precise way of making fibre-based robots; experimenting with a water-based solution to attach a 2D circuit to a fibrebot, creating a patterned sensor to track the robot’s movements.

The magnetic robots move the circuit onto the fibre, wrapping the sensor around the device. The magnet then moves upwards, drawing the robots together to form a pincher like grip to grab onto the circuit.

Impelled by these magnetic currents, the circuit is dragged towards the fibrebot. Once the circuit is positioned, the floating robots contract, drawing the fibre upwards and wrapping the circuit around it.

Performed in under five minutes, this manoeuvre is the first to equip a fibrebot with advanced forms of sensorial technology, a solution that is cheap and in the right hands, relatively easy to reproduce.

“I’m fairly certain that, except for the microscope, this process can be reproduced in a week for about ?200,” Bardot says. “Another thing that is really interesting with this technology is that instead of creating everything from scratch, we are building on the work of 2D electronics that has been developed over the last 50 years.”

Revolutionary opportunities

For Bardot, the success of this experiment is exciting due to the myriad of opportunities it unearths. A series of tiny steps forward rather than a leap, the robots delivering drugs and liquid biopsies could spur on faster, more accurate forms of cancer diagnosis.

“Microfluidics could be an interesting prospect for drug delivery and for liquid biopsies,” enthuses Bardot. “For cancer treatment, for example, you could run a small sample every hour and keep track of the process in real time, shortening the information loop, reacting faster as the cancer is evolving.”

Given some of the cutting-edge research being conducted, these predictions feel like the tip of the iceberg. For example, the Max Planck Institute for Intelligent Systems in Stuttgar have created miniature robots that can crawl, jump and swim through the body, contorted into shape by magnetic fields.

Meanwhile, scientists at the University of California have developed spider-like robots that carry coatings of platelets and red blood cells to neutralise bacteria and counteract toxins in the bloodstream.

Microrobots are also being touted as a radical new force in brain surgery, allowing surgeons to treat tumours and aneurisms without the need for invasive procedures such as a craniotomy.

These novel forms of treatment are currently being investigated by University of Toronto professor Jessica Burgner-Kahrs, who has been experimenting with robots that curve and snake through the body, avoiding vital organs to access specific tissues non-invasively.

For some these advancements might be ushering an age that ranks robotic precision over the intuitive understanding of medical professionals – an act that physicist Richard Feynman called “swallowing the doctor” – for Bardot, one can enhance the other.

“It’s about bringing more information to the surgeon for safer procedures and more precise methods,” Bardot says. ”Some people think it’s about replacement, but, for me, it’s about getting the best out of both the surgeon and the machine.”

However, more work is needed to investigate how micro-figures can be manoeuvred and equipped with sensors and short-form computers to help navigate the body, and report findings via feedback loops.

Once greater functionality is established, not only could these devices be used to enhance routine non-invasive operations, but they could unearth revolutionary new forms of surgery and diagnosis. After all, what is innovation, but a series of tiny, incremental changes that converge into one giant leap forward?