User:UCSBGasparini/sandbox/Purdue's μTUM Microrobots

= μTUM Microrobots =

Introduction:
Purdue's μTUM Microrobot is a magnetic microbot that can travel through the human colon without a battery or power source. This tiny robot, 400 μm x 800 μm, is powered via an electromagnetic force, generated by a gyrating magnet, that creates a rotational torque on the microbot. By flipping the axis of rotation of the magnet, the robot is capable of another dimension of movement. Therefore, the robot is able to flip sideways and lengthwise. In order to locate the flipping microbot in the patient's organ, researchers have developed a high frequency (greater than 10 Megahertz) ultrasound tracking system that allows the operator to precisely locate the device. The μTUM Microrobot project at Purdue started in 2017 and aims to begin human in vivo testing within the next few months. This robot has the ability to revolutionize medicine delivery and make minimally invasive surges like colonoscopies unnecessary.

Scientific Concepts:
The μTUM microbots must be propelled by an external magnetic field because they operate without a battery or hardwired power source. The nickel coated ends of the robot interact with a rotating magnet to achieve two dimensional motion. The robot can flip lengthwise and widthwise depending on the orientation of the magnet. When activated, the magnet exerts an external torque on the robot that is mapped by: “T⃗ m=VmM⃗ ×B⃗ where Vm is the magnetic volume of the robot, M⃗  is the microbot’s magnetization and B⃗  is the strength of the external magnetic field.” When the robot is lying horizontally the greatest magnet force is achieved if the magnet is oriented perpendicularly to the microbot. These microbots can operate in dry, wet, and steep conditions. Since the μTUM robots have no power source they cannot indicate where they are in the subject; this requires the researchers to use ultrasound imaging to detect the robot. This imaging technique was chosen because it does not create a magnetic field that could possibly disturb the robot, unlike magnetic resonance imaging, X- ray, and optical fluorescence imaging.

Construction:
The magnetic μTUM microbots were designed and developed at Purdue University by researchers: “Chenghao Bi, Elizabeth E. Niedert, Georges Adam, Elly Lambert, Luis Solorio, and David J. Cappelleri”. The microbots are constructed from SU-8,a negative epoxy photoresist, and polydimethylsiloxane, a “silicon based natural polymer”. The microbot is shaped like a flashdrive constructed out of SU-8 particles, with both ends of the microbot coated in NbFeB particles. This construction creates two polar fields on either end of the magnet allowing it to tumble when a magnetic force is applied. Previous iterations of the experiment were done with a spherical robot. However, the spherical robot needed to have a larger size in order to ensure it had enough friction to climb steep inclines, which made the robot too large to be functional. The rectangular shape of the microbot is much lighter and gives it a higher coefficient of static friction because it has a significantly larger surface area that is in contact with the ground at any given point which allows it to climb steep surfaces. In order to administer medicine, the robot is coated with the treatment and releases it slowly while it flips through the subject’s body.

Testing:
The goal of developing this microbot was to have a robot that could function in the environment inside the human body. To ensure the robot could perform in these harsh environments, researchers at Purdue conducted tests to prove the robot could overcome difficult terrain, these tests included a speed test, an inclined plane transversal test, and a mobility test. In the speed test the researchers recorded the speed the robot could travel in both wet conditions and dry conditions to find the average speed the robot could achieve in both environments. The average velocity of the robot in dry conditions was 48mm/s and in wet conditions the robot's average velocity was 13.6 mm/s. David Cappelleri and his team also conducted a gradient test where they tested the maximum angle the robot could climb. The gradient test proved the robot was able to climb a 45° and 60° incline in both dry and wet conditions with minimal difficulty. In the mobility test the researchers proved the robot can flip through a honeycomb terrain, a terrain with cylindrical bumps, and knurled surface. The robot is able to overcome these conditions by rotating on multiple axis instead of only flipping in one direction.

Benefits(impact):
The magnetic μTUM microbots will serve as an alternative to traditional invasive procedures, such as colonoscopies. The μTUM microbots' primary field of focus is targeted drug delivery. However, other implementations of this device include tumor imaging and ablation, microsurgery, tissue biopsies, cell delivery, and gene silencing. Due to the precision achieved by ultrasound imaging, doctors can accurately administer medicine. The microbot disperses medicine over the course of a one hour time period in a "sulfur buffered saline". Accurately delivering medicine decreases side effects like hair loss and bleeding which is common in these treatments. In addition, the miniature size of these robots makes traditionally strenuous procedures harmless and simple.