Robotically Steered Flexible Needles
Needle insertion into soft tissue is one of the most common minimally invasive medical procedures today (S. Misra, 2010). It is often used for diagnosis, sample removal from tissues deep within the body and localized therapeutic drug delivery. Typically, a rigid needle with a relatively large diameter would be used for these procedures.
Inaccurate needle placement can result in malignancies not being detected during biopsy, radioactive seeds not being placed in the correct location to destroy cancerous lesions during brachytherapy and potentially fatal effects during the administration of anesthesia (S. Misra, 2010).
The University of Twente has developed a robot-assisted system for steering flexible needles than can reach their intended target in tissue with sub-millimetre level accuracy (Bruysters, 2015). The needle has an asymmetric tip that causes it to naturally bend when inserted into soft tissue. By performing a sequence of insertions and rotations the needle can navigate complex three-dimensional paths. The needle is controlled by a robot using ultrasound imaging and a localization algorithm (Bruysters, 2015).
This system also allows the clinician to have control, using guidance and cues given by the robotic system through vibrations and visual feedback. This could allow a clinician to guide the needle from a different location to the patient (Bruysters, 2015).
The researchers believe that the system is 3-4 years away from starting clinical trials.
Reconfigurable modular robots have the potential to aid drug delivery and perform surgery within the human body by allowing a single system to navigate diverse environments and perform multiple tasks. Existing microbots can move or work effectively in homogenous environments and to complete a single specific task, but lack versatility (U Kei Cheang, 2016).
Researchers at Drexel University have demonstrated how using a rotating magnetic field, multiple chains of microscopic magnetic bead-based robots can link and unlink in a modular fashion into microrobots with different physical characteristics, whilst swimming at impressive speeds through a liquid (Faulstick, 2016).
The robot chains move by spinning like a long screw-shaped propeller, controlled by an external rotating magnetic field. Increasing the rotational velocity of the field will result in the robots spinning faster. This is also the mechanism for dividing the robot into shorter segments, at a certain rate of rotation the chain will split into two smaller chains that can be controlled independently.
They can then be re-linked at the optimum rotation rates and angle of approach. This technology could travel inside the body and decouple to deliver a medicinal payload of treatment to a specific, targeted part of the body (Faulstick, 2016).
Researchers at the University of Sheffield, MIT, and the Tokyo Institute of Technology have developed and demonstrated an ‘origami’ robot, which is swallowed as a capsule and unfolds inside the human body. It is then steered by external magnetic fields to crawl and perform specific tasks such as recovering foreign objects, patch wounds, or deliver medicine (Hardesty, 2016).
The robot has two layers of structural material sandwiching a material that shrinks when exposed to heat, the shape of the robot is determined by a pattern of slits in the outer layers when the middle layer contracts. There is a permanent magnet in the center that responds to changing magnetic fields outside of the body. In order to move, an application of a magnetic field causes the body to flex, and friction between the front feet and the ground is great enough that the front feet stay fixed while the back feet lift.
Another sequence of magnetic fields then causes the robot’s body to twist slightly, which breaks the adhesion of the front feet and the robot moves forward.
3,500 button batteries are swallowed in the US every year if they come into prolonged contact with the esophagus the battery can burn the tissue and become embedded (Hardesty, 2016). This robot could remove the battery without surgery, manually transporting it through the digestive system. The device is biodegradable, so after performing its task it dissolves safely into the digestive system.
The researchers at MIT aim to develop the origami robot to become autonomous through the use of sensors. This would eliminate the need for external control via a magnetic field.
References and Further Reading
Robotically Steered Flexible Needles Navigate in Tissue
Drexel's Microswimmer Robots Can Work Together - And Apart
Ingestible Origami Robot
S. Misra, K. B. R. B. W. S. K. T. R. a. A. M. O., 2010. Mechanics of Flexible Needles Robotically Steered through Soft Tissue. The International Journal of Robotics Research, 29(13), pp. 1640-1660.
U Kei Cheang, F. M. H. K. K. L. H. C. F. &. M. J. K., 2016. Versatile microrobotics using simple modular subunits. Scientific Reports, Volume 6, p. 30472.
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