Medical Technology: Little Robot and the Seven Dwarfs

30. November 2015
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Capturing vital signs, removing a thrombosis or administering drugs in a targeted manner: robots are already fulfilling such tasks at a micro or nano-level in the laboratory. Experts estimate that over the next decade many such devices will come to benefit patients.

People have been dreaming about it for centuries: we fall ill, yet no surgeon has to reach for a scalpel. Rather, it’s microscopic robots that make their way into our bodies and perform operations or administer medical agents in a targeted manner at the scene of the event. In the laboratory, doctors and engineers have jointly managed to overcome technical difficulties: a great step towards application in use.

Modular or Origami

The first question: How do these tools manage to do their work in our bodies? This is achieved through reconfigurable systems. Doctors inject – currently still only as part of laboratory projects – a large number of small, partially identical modules in the body. By way of intelligent combination, larger functional groups with different characteristics emerge. They reach locations which are difficult to access by tradition means in order to take biopsies, perform surgery or offload substances.

At the International Conference on Robotics and Automation (ICRA) MIT researchers presented microrobots that resemble origami figures. They consist of films and can move around or swim, thanks to neodymium magnets and electromagnetic coils beneath their surface. Their speed limit sits somewhere between three and four centimetres per second. The new mini drone transport small loads. These could be drugs or radioactive seeds. Smaller obstacles such as blood clots are successfully crossed.

A special juice

Challenges still remain. In order to be able to travel around in the blood or in synovial fluid, it is important that viscosity of human body fluids be taken into account. Spirally formed appendages, such as nature uses when building bacteria, proved to be too complex. But the challenges don’t end there: most biological fluids are not Newtonian fluids with constant viscosity. Their properties vary according to movement speed.

Researchers at the Max Planck Society are now investing efforts in an internal drive system in their micro-swimmers. A working group has been able to produce miniaturised silicone shells via 3D printing. Their structure could easily pass through blood vessels. In order to get around, both shell parts fold up quickly, but slowly open again – thanks to magnetic control. The viscosity between the two halves changes, and so the journey begins. Here, too, one aim is that of administering medications locally.

Fresh fish in the body

Speaking of 3D printing: scientists from La Jolla are investing efforts in three-dimensional techniques so as to produce the smallest, fish-shaped workpieces [Paywall]. Using Microscale Continuous Optical Printing (μCOP) they produce several hundred micro fish within a few seconds. The heart of the μCOP is a digital micro-mirror array with two million micro-mirrors, each of which can be individually controlled in order to steer UV radiation and have it projected onto light-sensitive layers. In the tail region nanoparticles have been coated with platinum – as a catalyst, in order to use chemical energy. Solutions of hydrogen peroxide serve as a medium; the molecule breaking up under catalysis into water and oxygen. Enzymes would be suitable for energy production for further inserting processes in the body. On top of that, researchers placed iron oxide particles in the “head” of their microfish: an option for external control via magnetic field. They are now trying to transport medications in microencapsulated form. Having reached their target the devices release the pharmaceutic product, which permits locally high concentrations without burdening the entire organism – visions out of the future for the eyes of doctors in the present.

Saw in the blood vessel

Experiments involving miniature grippers sound similarly futuristic. John Hopkins University reports having early successes using artificial “starfish”. Small “grippers” claw their way through vascular occlusions by changing shape. Temperature-sensitive versions can however also carry out biopsies. They shoot their mini tentacle at higher temperatures while passing by; in so doing they take tissue samples. It’s precisely here that added value is to be found: whereas gastroenterologists today take only individual samples for colonoscopies, “Micro Grippers” distribute themselves statistically throughout the entire intestine. If doctors put thousands of these devices into action, the statistical probability of overlooking malignant tissue drops. After the job has been done colleagues gather the minute sample hunters using commercial bar magnets and send them to the lab.

This gets into your eye

Innovative research is in no way restricted to the intestine. It’s in the vitreous body of the eye where these smallest of devices can demonstrate their strong point. The latest example: a combination involving fluorescent dyes was led to a special type of sensor. When oxygen saturation varies, differences show up in the fluorescence spectrum. Particularly with high-risk patients there exists the possibility to transfer measurements from the doctor’s office to the patient living his or her everyday life. Laymen could regularly examine themselves and transmit readings via app to an ophthalmologist – an opportunity to conduct close monitoring. High-minded goals – now things are moving from the laboratory to the animal model and then into the clinic.

 

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