If you’ve ever taken the same round pill for stomach cramps, headaches, and anything else, you already know that medicines aren’t always made to treat specific pain points.

While over-the-counter medications have long been used to treat a variety of maladies, biomedical researchers have only lately begun to investigate strategies for better-targeted drug delivery when treating more complex medical conditions such as cardiovascular disease or cancer.

The millirobot represents a promising breakthrough in this rapidly expanding field of biomedicine. These fingertip-sized robots have the potential to save lives in the future by crawling, spinning, and swimming into tight locations on their mission to inspect inner workings or distribute medicines.

Renee Zhao, a mechanical engineer at Stanford University, is leading research in this subject and is working on a number of millirobot designs at the same time, including a magnetic crawling robot that was recently featured worming its way into a stomach on the cover of Science Advances. Her robots can self-select different locomotive modes and overcome impediments in the body thanks to magnetic fields, which allow for continuous motion and can be applied instantaneously to generate torque and change the way the robots move. By changing the strength and direction of the magnetic field, Zhao’s team can send the robot flying across the body at speeds 10 times the robot’s length in a single leap.

The magnetic actuation is a key part of her research. It lets her control the device without being tied to it, and it separates the control unit from the device so that it can be made smaller. Zhao said that their most recent robot, which was featured in Nature Communications this month, is “the most robust and multifunctional untethered robot we have ever developed.”

As its name implies, this new “spinning-enabled wireless amphibious origami millirobot” can do a wide variety of tasks. It’s a beautifully designed single unit that can quickly move across the slick, uneven surfaces of an organ and float through human fluids, propelling itself wirelessly while conveying liquid medicines. Rather than swallowing pills or injecting liquids, this robot withholds medicine until it “reaches the target, and then releases a high-concentration drug,” according to Zhao, an assistant professor of mechanical engineering. “That is how our robot achieves targeted drug delivery.”

Changing the way drugs are delivered

According to Zhao, what makes this amphibious robot unique is that it goes beyond the designs of most origami-based robotics, which rely solely on the foldability of origami to regulate how a robot morphs and moves.

The team led by Zhao analyzed not only how folding may allow the robot to do particular activities — for example, an accordion fold that squeezes out medicine — but also how the dimensions of each fold’s exact shape effected the robot’s stiff mobility when it was not folded. Therefore, as the robot unfolds, its shape naturally facilitates movement. Such considerations helped the researchers to get more usage out of the materials without adding bulk, and in Zhao’s universe, the less invasive the medical treatment, the more usefulness accomplished from a single structure in the robot’s design.

The integration of various geometrical characteristics is another unique aspect of the robot’s design. A longitudinal opening in the robot’s center and lateral slits inclined up the sides helped the robot swim better by reducing water resistance. “This design induces a negative pressure in the robot for fast swimming and meanwhile provides suction for cargo pickup and transportation,” Zhao explained. “We take full advantage of the geometric features of this small robot and explore that single structure for different applications and for different functions.”

The Zhao Lab is discussing with the Stanford Medical School’s faculty the best ways to advance medical practice through the development of novel technologies. If Zhao’s experiment succeeds, her robots would not only give a convenient means to effectively dispense medicine, but they will also be able to carry equipment or cameras into the body, potentially revolutionizing how doctors evaluate patients. The company is also researching using ultrasound imaging to track where robots travel, obviating the need for organs to be cut open.

Better with less

While we won’t see millirobots like Zhao’s in real-world situations until more is understood about optimal design and imaging best practices, the lab’s first-of-its-kind swimmer, featured in Nature Communications, is one of their most advanced robots. It is now in the trial stages, which precede any live animal testing that will follow human clinical trials.

Meanwhile, Zhao’s group is working on merging a variety of revolutionary smart materials and structures into distinctive designs that will eventually result in new biomedical devices. She also intends to continue scaling down her robots in order to do microscale biomedical research.

Zhao, as an engineer, seeks to create the most functional structures possible. Her amphibious robot embodies that objective, as it inspired her team to think more deeply about geometric characteristics that other origami robot researchers had not yet prioritized. “We started looking at how all these work in parallel,” Zhao remarked. “This is a very unique point of this work, and it also has broad potential application in the biomedical field.”

Image Credit: Zhao Lab

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