(Images Courtesy of “The Sentinel Collection” http://www.collectiondx.com/toy_review/2003/sentinel

Introduction:I was always fascinated with the Sentinels from the 1999 Movie “The Matrix” starring Keanu Reeves. These fictional robots look like a cross between insects, viruses and octopi. What I found cool is the fact that the robots could find the “prey” and attach to many surfaces, both organic and metallic. (If you have never seen this movie, check out the video clip below so you can have an idea of how this unique robot moves).

YOUTUBE VIDEO FROM THE MATRIXI did some reading on medical nanorobots that are capable of moving through the aquatic environment of the human blood stream (and therefore an aquatic locomotion) and I wonder if tiny nano-sized versions of the sentinels from the Matrix could be manufactured that could be use to target and destroy cancer cells, sequester viruses or crawl through specific tissue and repair damaged cells or cell parts.

“The Sentinel” Bio-Inspired Medical Nanobot

The basic definition of Nanotechology in terms of hierarchy in design:

Nanotechnology is the engineering of functional systems at the molecular scale.This covers both current work and concepts that are more advanced. In its original sense, 'nanotechnology' refers to the projected ability to construct items from the bottom up using molecular techniques.

“The science, engineering, and technology related to the understanding and control of matter at the length scale of approximately 1 to 100 nanometers.”

Bioinspiration:There are many adaptations derived from many organisms that played a role in my first and second designs. Just the like the Ted Talks Video we watched from Dr. Fuller (with all of the foot adaptations from so many species that went into one robot design) I took ideas from a few different organisms including:• The crystal like surface -receptors from a bacteriophage virus• The rotary motors of the bacterial and sperm flagella that propel the organism forward.• The bristle-like extensions and gears found on the legs of insects (as in our week 3 class

readings and videos.• The flexible nature of octopus arms and the ability to perform multiple tasks

simultaneously.

Biomedical Applications:The robot will be capable of performing repair of damaged tissue using controlled remote response and, attack foreign bodies or cancer cells and be able to deliver medicines to specific target tissues by either the remote control release or surface contact stimulus.

Designs• Design 1

• This one was a bit TOO ambitious! Brief explanation:• The propulsion would be achieved using a nanomotor assembly that would mimic

the system utilized by a bacterial flagellum. (Videos to follow). The best candidate material would be carbon nanotubes although synthetic DNAʼs have been used. The Benefit of using modified organic materials such as DNA/RNA or any modified amino acids for a motor unit is that ATP or any NTP could be used to power the machine using the organisms own supply, just like in a real bacterium. The hinges on the motor assembly would allow the arms to move forward and backward, perhaps by using the nano-gears as seen on the legs of insects or the hinges found in insect joints. The receptors on the front of the nanobot would interact with the surface of the target by either chemical interaction or magnetic fields.

• Design #2:• I changed the original design; I got rid of the octopus-like arms and reduced the

locomotion generators to a few back rotors like a bacterium; I decided to make the robot more of a deliverer of medicines and/or doses of radioactive materials that utilizes a geared-release mechanism. The cavity in the center of the nanobot is attached to surface fibers that are in turn held together by a gear system. The materials for the gears would be composed of a stiffer polymer like chitin while the receptor fibers would be composed of something more flexible. The receptor molecules themselves at the tips of the fibers would have to be attached by some sort of covalent linkage, similar to an antibody. The fibers that make up the nanogears would most likely be composed of carbon nanofibers and silicon. Synthetic nucleotides and synthetic amino acids with ATP binding sites showed up in the literature and would be excellent candidates because they can be powered by materials already found in the human body.

DESIGNS BORROWED FROM NATURE:1. The propulsion will be achieved using the flagellar motor assembly inspired by the

human sperm and bacterial flagellum. (See diagram below:)

• YOU TUBE VIDEO LINK TO ACADEMIC DESCRIPTION OF THE MOTOR

a. Example of inspired robot design (“twisting artificial muscles) from Dr Javad Foroughi, Prof Geoff Spinks and team at the Intelligent Polymer Research Institute at the University of Wollongong, part of the ARC Centre of Excellence for Electromaterials Science. (Published in SCIENCE, 2012 October 11.)

YOU TUBE VIDEO OF NANOBOT-INSPIRED ARTIFICIAL FLAGELLA

b. Proposed Medical Robot (proposed design) Taken from “How Stuff Works”

2. Gears inspired by the insect gear systems covered in Week 3 Lecture notes. The gears would act as a interface between the “receptor fibers” on the front of the robot and the “expandable sac” within the robot. As the receptor fiber interacts with the molecules on the targetʼs surface, the conformation changes will move the expandable “sac” within the robot releasing its contents, or could be an injectable assembly like a virus, into the target. The motion is automatic and the gears would capture that forward motion and translate the motion into the robotʼs interior. (See Figures below)

a). Gears inspired from Insects: (Photos from Week 3 Lecture notes)

" " " " (Images: Ed Yong, September 2013, Phenomena.NationalGeographic.com

b.) The diagram below is an example of nano-gears composed of carbon-nanofibers. These would be incorporated into the medical nanobot. The construction of the carbon -fibers is proposed to be done by virus-directly assembly similar to the process discussed in this weekʼs Ted Talks by Angela Belcher (Virus-assembled Batteries..see source list),

c.) Cell-Signaling and Surface Receptors. The robot would exhibit some type of surface reception similar to that found in cell-surface communication. When the robot reaches its target, the molecular conformational changes will cause the gears to move and that motion will drive the released of the robotʼs inner contents (medicine, radioactive probes, whatever needs to be delivered to specific target). For a review of surface reception, I have included the Bozeman Video I used in my class:

YOUTUBE VIDEO LINK TO BOZEMAN DISCUSSION"

Technical Challenges of Aquatic Locomotion of Nanobots in fluids / Physical Limits

• In an aqueous environment, the biggest challenge becomes friction (or drag) from the fluid.

• The density of the robot is important since you donʼt want the robot sinking or floating to the top of the blood vessel so the density of the robot should be such that it matched that of the blood (same specific gravity)

• Newtonʼs Third Law applies here; in order for an animal to move FORWARD in an aqueous environment, the fluid must be pushed BACKWARD; therefore the animal (ROBOT) must have an efficient means of pushing the fluid backwards to move towards its target within the blood stream. This becomes a huge problem the SMALLER the robot becomes. See the video below that explains the problems of moving nano-sized objects through a liquid medium:

• YOU TUBE: THE PHYSICS OF SPERM AND SMALL ORGANISMS:

• Powering the robot: how can the robot be powered at such a small scale? Suggestions include using the bodyʼs own ATP source; if the nanomaterial at the motor was composed of synthetic amino acids with ATP binding sites, than the motor can use this as a source. Other ideas include using “SEEBECK EFFECT” (see below), tiny capacitors, nuclear power of magnetic fields applied from an external source to drive the robot within the body.

• SEEBACK EFFECT: The Seebeck effect occurs when two conductors made of different metals are joined at two points that are kept at two different temperatures. The metal conductors become a thermocouple, meaning that they generate voltage when the junctures are at different temperatures.

Since it's difficult to rely on temperature gradients within the body, it's unlikely we'll see many nanorobots use body heat for power. (Source: HOW STUFF WORKS).

• How will the nanobot be recovered, removed? This is a big challenge. Method that I found in my research mainly focused on using ultrasound waves to break up the nanoparticle into sizes that can be easily excreted. Other methods include the use of magnetic fields to guide the particles to the kidney for excretion. Also, using the immune system to remove the particles has been suggested as well. This is a problem that is being researched intensely.

Current Medical Nanobot Prototypes:• “Cyberplasm” is a medical nanobot constructed that is designed to detect cancer cells

Image: 17 March, 2014 in Science. Tags: Cyberplasm, Cyberplasm - a new disease detecting nanobot for humans, disease detecting nanobot for humans

• “Cancer Destroyer” designed by Japanese company; still too big for human use.

FInal Notes:One thing really fascinated me when I performed my research is that nanotechnology was introduced to the science arena by Richard Feynman back in the 1950ʻs. He challenged his graduate students to design a machine that would fit inside of a cube 1/64th of an inch on all sides. It was this challenge that spark the development of the field of nanomachines. (How Stuff Works).

When I teach cellular biology, I refer to the cell parts as machines. I think my students have a better grasp of molecular biology if I can use machine analogies. I believe nature natureʼs molecular machinery is truly the key to building more efficient systems from everything to energy to medicine.

The following is an excellent summary from a TED TALKS video on the challenges of constructing nanorobots for medical applications:

LINK TO TED TALKS VIDEO MEDICAL NANBOTS

Sources:

Barker, Veronique. "Fantastic Voyage - From Fiction to Reality." innovation Canada.ca. July-August 2007, Issue 29.

Burrows & Sutton. 2013. Interacting Gears Synchronize Propulsive Leg Movements in a Jumping Insect. Science http://dx.doi.org/10.1126/science.1240284

Cavalcanti, Adriano, et al. "Nanorobot for Treatment of Patients with Artery Occlusion." Proceedings of Virtual Concept, 2006. Cancun, Mexico.

Cavalcanti, Adriano. "Nanorobotics." NanoScience Today. September 13, 2004. http://www.geocities.com/cbicpg/nanoscience/NST2004/nanorobots.htm

Griml, Guy. "Israeli scientists unveil mini-robot that can travel through bloodstream." Haaretz.com. July 17, 2007. http://wwwhaaretz.com/hasen/spages/875277.html

Hyperphysics. http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html. (Physics Laws)

"Israeli scientists invent smallest robot to deliver drugs through blood vessels." China View. June 27, 2007. http://news.xinhuanet.com/english/2007-06/27/content_6300084.htm

Knight, Will. "Drugs delivered by robots in the blood." NewScientist.com. October, 2004. www.newscientist.com/article/dn6474.html

Rubinstein, Leslie. "A Practical NanoRobot for Treatment of Various Medical Problems." Foresight Nanotech Institute. http://www.foresight.org/conference/MNT8/Papers/Rubinstein/index.html

Strickland, Jonathan. “How Nanobots Will Work.” How Stuff Works.http://electronics.howstuffworks.com/nanorobot7.htm

"Technion Researchers Find Way to Move Swimming Robot Through the Human Body." Technion University Press Release. October 29, 2006. http://pard.technion.ac.il/archives/presseng/Html/PR_swimmersENG_29_10.Html

Video Sources:

Robert fuller Ted Talks...do not attempt to mimic nature...be inspired by it!!http://www.ted.com/talks/robert_full_on_animal_movement#t-1133787

The physics of sperm TED TALKS: https://www.youtube.com/watch?v=U9g4gRWkFTs

Ted Talks: Building Medical Robots: https://www.youtube.com/watch?v=DfV8xu2nHy4

Nanotech You Tube: Twisting medical muscles: https://www.youtube.com/watch?v=JQdu8d3EUaY

Octopus Robotics https://www.youtube.com/watch?v=Gvx8GwTCx_A