Micro – robots - spermatozoa

Recently, we reported on the development of biomechanical "spermatozoa", the movement of the tails of which occurs due to the reduction of muscle cells attached to them. Now researchers from the University of Twente (the Netherlands) and the German University in Cairo have developed completely inorganic micro-robots in the form of spermatozoa, called MagnetoSperm, whose movement can be controlled using a weak alternating magnetic field.

MagnetoSperm moves in a weak alternating magnetic field.

The microrobot, whose length is 322 microns, is made by uniformly applying a 5-micron layer of SU-8 polymer to the silicone base, selected due to ease of manufacture and mechanical stability, and then "cutting out" by standard photolithography. After that, a cobalt-nickel layer is applied to the "head" of the micro robot using electron beam sputtering technology.

When placed in an alternating magnetic field with an induction of less than 5 millitesla (which roughly corresponds to the field created by decorative magnets on the refrigerator), a magnetic torque acts on the head of the micro robot, which causes vibrations of the "tail" that ensure the movement of the micro robot forward. The direction of movement of the micro robot can be set by changing the direction of the magnetic field lines.

According to the head of the study, Dr. Sarthak Misra, their micro-robots can be used to perform a variety of biomedical tasks, including drug delivery, in vitro fertilization, cell sorting and artery cleaning.

Schematic representation of the manufacture of MagnetoSperm. A layer of SU-8 polymer with a thickness of 5 microns is applied to a silicone substrate (a), after which the base of the micro robot is cut using the method of standard photolithography (b, c). Using a resistant mask for reverse lithography (d) by electron beam spraying, a Co80Ni20 element with a thickness of 200 nanometers is formed on the head of the micro robot (d, e). MagnetoSperm is released by immersing a silicone substrate in a 5% solution of tetramethylammonium hydrochloride at 85 degrees Celsius. The maximum and minimum diameters of the ellipsoid head of the micro robot (in the micro–image below) are 42.6 microns (a) and 27.6 microns (b). (Figure from the article in Applied Physics Letters.)

In the future, the researchers hope to further reduce the size of the already very small MagnetoSperm robots. Currently, they are developing a method for the production of magnetic nanofiber, which will act as a moving "tail" of a micro robot.

Article by Islam S. M. Khalil et al. MagnetoSperm: A Microrobot that Navigates using Weak Magnetic Fields is published in the journal Applied Physics Letters.

Evgeniya Ryabtseva
Portal "Eternal youth" http://vechnayamolodost.ru based on AIP Publishing: Here Come the "Brobots".

05.06.2014