An Introduction to Surgical Microbots

This article was updated on the 3rd October 2019.

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A study by Watson B, et al (2010), conducted at Monash University, Australia, developed a micro-motor using piezoelectric material to create a drive system for in vivo surgery.

It is hoped that complex surgical procedures used to treat cerebral complications, such as those seen in stroke patients, will be more effective when using a small swimming robot (a micro-robot), that can get to small vascular components. This procedure is otherwise near-to-impossible with standard operating tools.

The motivation behind engineering such state-of-the-art robotic technology comes from complicated invasive procedures such as neurosurgical and cardiovascular surgery (also termed minimal access surgery).  Here, the likelihood of error and strain is increased and could result in prolonged pain, delayed recovery time, or in extreme cases, death or serious injury to the patient.

The idea of developing microbots with the functional capacity to conduct intricate in vivo surgery is set to revolutionize invasive medicine as we know it. Piezoelectric motors have been tested as micro-motor robots, though research into ultrasonic resonant motors has yet to be tweaked to meet performance requirements. The basic architecture to a piezoelectric resonance motor involves a resonant stator mode that generates circular motions at the tip of a stator. The stator itself is made of piezoelectric material that banks an array of electrodes to generate an electrical impulse.

A basic prototype introduced by Watson et al. (2010) was made of helical grooves and a magnet that works to balance the axial, torsional, and electro-magnetic resonance.

The structure can be broken down into five distinct parts: a power supply, a piezoelectric element, a stator, a rotor, and the flagellum. The stator axial moves back and forth and the stator torsional force vibration mode moves in a spiral fashion. Both the stator and torsional vibration mode work as one unit and force a stator-tip motion to occur. The spiral-circular motion of the stator tip forces the rotor to move the flagellum (see detailed animation below). The micro-robots, if designed to carry micro-needles, micro-pumps, and force, could then help perform intricate surgical tasks that would otherwise pose a risk to surrounding tissue if using larger surgical tools.

Working Example

A group of researchers at the Institute of Robotics and Intelligent Systems part of the Swiss Federal Institute of Technology-Zürich (ETHZ) are currently developing micro-robots for invasive eye surgery. The micro-robots are being designed to move magnetically through the vitreous humour of the eye.

The use of an external magnetic controller is used to maneuvrer the micro-robots and guide them towards specific target points. This is an exciting approach for modern-day medical technology and is also set to pave the way for drug delivery systems. The video above is a news release demonstrating how micro-robots are being applied in eye surgery today.

The micro-robotic device is controlled by an external magnetic field. Though an exciting and smooth technique, a great deal of precision is required for controlling the movement and for guiding the micro-robot to the target site. This is a rather complex technique which can further profit from future development.

If perfected, this novel technique could see medical procedures such as drug delivery to the eye and the re-construction of retinal tissue achieved alongside with an increased level of precision and accuracy. Conditions such as macular degeneration will favor in this instance because treatment of this and similar diseases require the direct delivery of drugs to a retinal vein, which is quite specific and carries high risks.

Advantages

One of the main advantages to the application of micro-robots in surgery is the decreased chances of an injury following invasive surgical procedures. There is also the added advantage of greater accuracy, particularly as the micro-robot is controlled externally. Use of micro-robots that involve needle insertion also helps reduce workspace limitations though this is controlled by a macro-robot device positioned at a particular location in the operating space.

Disadvantages

One of the biggest questions regarding surgical micro-robotics remains its power supply. It is fundamental that a power supply is sufficient to control the performance of micro-robots during an operation period, which can occasionally take up to several hours. A lack of energy supply during an operation will be a dangerous risk to the patient.

There also needs to be further research on geometric limitations to micro-robots and focus on how sensitive human tissue actually is to a robot system when considering exposure to radiation. Battery capacity also needs to be taken into consideration when understanding the operational period and the ability of a battery to deliver a particular electrical current at a precise voltage.

Future Direction

To focus on…

• Possible human limitations that could restrict the use of micro-robotics in surgery.
• Ways to improve the safety of micro-robot application in surgical procedures.
• The impact of micro-robotics on healthcare costs and patient recovery.
• Using micro-robots to achieve effective drug delivery.

Sources

• Siciliano, B., Khatib, O. (2008). Springer Handbook of Robotics. Germany, Berlin: Springer Science and Business Media.
• Gulrez, T., Hassanien, A.E. (2012). Advances in Robotics and Virtual Reality. Germany, Berlin: Springer Science and Business Media.
• Rosen, J., Hannaford, B., Satava, R.M. (2011). Surgical Robotics: Systems Applications and Visions. UK, London: Springer Science and Business Media, LLC.
• Watson, B., Friend, J., Yeo, L. Modelling and testing of a piezolelectric ultrasonic micro-motor suitable for in vivo micro-robotic applications. Journal of Micromechanics and Microengineering. 2010. 20: 115018.
• Edd, J., Payen, S., Rubinsky, B., et al. Biomimetic Propulsion for a Swimming Surgical Micro-Robot. Published in IEEE/RSJ Intelligent Robotics and Systems Conference, Las Vegas, USA, October, 2003.