Fabrication of Magnetic Ferrofluid Microrobot for Tissue Mechanical Measurement

Ferrofluids are a uniform mixture of magnetic nanoparticles and a carrier liquid, such as water or oil. They have become increasingly popular in the medical field due to their biocompatibility, manipulability, and their wide range of possible medical applications, one of them being mechanical measurement in human tissues. Our goal is to fabricate a bio-compatible ferrofluid droplet to perform these mechanical measurements. To fabricate the ferrofluid, magnetite nanoparticles (Fe3O4) were chosen along with vegetable oil as the carrier liquid due to their biocompatibility. The magnetic nanoparticles were also coated with oleic acid to serve as a lubricant layer to prevent them from agglomerating. We first coated the magnetic particles (Nanoshel) with oleic acid (Sigma). The magnetic particles were added to distilled water that was heated up to 60oC and mechanically stirred at 500 rpm. For each gram of magnetic nanoparticles used, an equal amount of oleic acid was added into the mixture and stirred for 15 minutes. The coated particles were then rinsed with distilled water followed by ethyl alcohol and dried. To fabricate the ferrofluid, we mixed the vegetable oil with the nanoparticles overnight to ensure uniform mixing with weight rations including 30%wt, 40%wt, and 50%wt, to find the optimal ratio for magnetic control and stability. To validate the technology using ferrofluid to perform tissue mechanical measurement, a droplet of ferrofluid was injected into the agar gel mimicking the stiffness of tissue and then actuated with a magnet. The ferrofluid showed observable deformation under a microscope after magnetic actuation. Our next steps will include repeating this process under a controlled gradient magnetic field while using a camera to track its deformation and movement and from there the hope is to perform on human tissue.