Modeled after an octopus sucker
The porous hydrogel moved the soft tissues without damage
Grigory Kopiev, N+1
Scientists from the USA, South Korea and Japan has developed a grip for small fragile and fragile objects – for example, fragments of living tissues. It consists of perpendicular channels that can expand and contract under the action of heat and thereby increase or decrease the level of adhesion. The article was published in the journal Science Advances (Kim et al., Electrothermal soft manipulator enabling safe transport and handling of thin cell/tissue sheets and bioelectronic devices).
In recent years, scientists and doctors have made great strides in creating artificial tissue constructs, including thin films with a thickness of several cells. Developments on mesh electrodes for recording the activity of neurons or vice versa their stimulation have also advanced. In both cases, when implanting tissue or electrodes, doctors have to deal with objects that require very careful handling.
Scientists led by Hyunjoon Kong from the University of Illinois at Urbana-Champaign and Yonsei University has created a flat grip capable of attaching to thin samples. The main part of the grip (which is in contact with objects) – this is a round film with many microchannels. The researchers created it by freezing PNIPAAm-hydrogel. They placed an aqueous solution with precursors on a vessel with liquid nitrogen. Because of this, the aqueous part of the solution began to solidify and form separate crystals, and the remaining components, due to reduced solubility, began to concentrate on the edges of the crystals. Another important detail of the process is that, since nitrogen cooling was carried out only on one side, a temperature gradient appeared in the solution and ice crystals grew from the bottom to the top of the vessel. As a result, it formed columnar ice crystals with small (about 200 nanometers) walls of a polymer precursor between them, which was then polymerized using ultraviolet radiation. After removing the ice, a hydrogel plate with vertical channels with an average diameter of about 20 micrometers remained.
The design of the manipulator. Drawings from the article by Kim et al.
This plate is able to hold objects due to the combination of its structure and material properties. The fact is that the hydrogel of which the plate consists, when heated above 32 degrees Celsius, turns into a dehydrated state and significantly decreases in size. When the plate is heated, its channels decrease and a negative (relative) pressure is formed in them, which presses the propped object. For the convenience of heating, the researchers glued an array of copper electrodes to the top of the plate, which, when current is applied, quickly and evenly increases the temperature and thereby activates the capture. To capture an object, the plate must be heated, propped up, then stop heating so that it cools down and the microchannels decrease, move to the right place and expand the channels again by heating.
The scheme of operation of the manipulator.
After assembling the capture, the authors showed its potential use in medicine. In one demonstration, they successfully transferred a film from myoblasts to muscle tissue, in another they managed to deliver a film from stem cells to the cornea of a live rabbit and then confirmed by histological examination that the stem cells attached to the upper layer of the cornea. They were also able to move an array of micrometer-thick electrodes to the surface of the pig's heart without damage. After that, they stimulated the muscles of the heart with the help of additional electrodes and read the activity with an array of electrodes applied using a new capture. The read-out readings were almost identical in shape to those fed to the stimulating electrodes.
You can see how it works here.
Portal "Eternal youth" http://vechnayamolodost.ru