Scientists Look Towards Octopus Suckers to Move Sensitive Electronics and Tissue

29-10-2020 | By Sam Brown

Researchers have developed a special heat-activated sucker that allows for the easy transfer of printed electronics and organic tissues from one surface to another. What challenges do flexible printed electronics pose, how does the sucker technology work, and how will it help with the manufacturing of printed electronics?

Why are flexible electronics and tissue problematic?

Most electronics applications utilise ridged structures that have little flexibility. Even electronics found in wearable devices are still ridged, and take advantage of material to provide flexibility when attaching the device to the wearer. However, truly flexible electronics are often incredibly thin, and as a result, can be easily destroyed. Thus, when thin-film electronics are designed they need to either be built directly to the target surface or use complex methods to transfer the device from the substrate it was made on to the substrate it will be attached to. The same issue occurs with tissue cultures; they can be easily grown in a Petri dish or other specialised medium, but transferring them from the substrate to the target surface (such as living tissue), is extremely difficult.

One method around this is to manufacture such components onto the target surface directly, but this is not always possible. For example, many printed, electronic processes require specialised sintering which involves high temperatures, and sintering these materials on human skin would result in burns. Growing tissue on a living organism is also ineffective as it may be hard to maintain ideal conditions to grow the tissue sample (such as moisture content, sugars, and light). 

How does the “octopus-like” sucker technology work?

Researchers from the University of Illinois-Urbana Champaign have developed a sucker inspired by the octopus to move sensitive tissues and printed electronics from the manufacturing substrate to the target substrate. As demonstrated in the video, attempting to pick up thin tissue samples (this also includes thin-film flexible electronics), is very challenging, and can result in damage to the flexible layer. 

The sucker operates similarly to octopus suckers whereby the shape of the sucker is partly deformed to create a partial vacuum. This partial vacuum keeps the ultra-thin layer attacked to the sucker whereby it can be moved to the target substrate, and when the pressure is equalised, the layer is transferred to the new substrate. 

To create the sucker, the team took advantage of a temperature-responsive layer of hydrogel that was attached to a heater. Upon being heated, the hydrogel shrinks resulting in the air cavity of the sucker to reduce. Once heated, the sucker is placed onto the sheet, and the heater turned off. The cooling results in the expansion of the hydrogel, but the sheet prevents air from filling the sucker and thus remains attached to the sucker. When the sucker is placed onto the final substrate with heat applied to the sucker, the sheet detaches from the sucker. While the sucker has demonstrated to be useful in transferring tissue and thin-film electronics, the team now intends to integrate electronics into the sucker, including pressure sensors. The use of such sensors will allow the sucker to obtain feedback from the item it is holding, and thus make adjustments as needed when holding different objects. 

What other technologies may improve sensitive electronics and tissue handling?

The use of suckers to pick up objects is something already used in the industry and is a prevalent method thanks to its ability to work with a wide range of surfaces. When it comes to picking up sensitive materials such as tissue, suckers do not tear or wrinkle the layer, but suckers also have the advantage that they do not use a mechanical crushing force (i.e. pair of jaws) to lift items. A good task that demonstrates the difficulty with traditional grabbers for lifting objects is the ability to pick up an egg; too much force and the egg breaks, too little force and the egg falls. While a gripper can be refined in the amount of force applied, the gripper may be required to pick up a wide variety of different objects on the fly, all of which require different amounts of force.

One good alternative to the traditional griper is air grippers. This type of gripper, like air suction, relies on a pneumatic principle to operate but instead of generating a vacuum, it forces air into small fingers that open and close. When air is pumped in, the fingers grab and hold an item, but the use of soft parts means that the fingers apply force and deform around the surface. This allows them to pick up many different objects without needing to be reprogrammed for each object type. However, such systems are still inappropriate for thin-films and tissue.

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By Sam Brown