February 21, 2024

In recent years, we’ve seen wood being used to make traditional non-wood items like transistors, bicycles and drones. Now, scientists have used the stuff to create a robotic gripper…and it definitely has a selling point.

Often, robot designers must choose between soft rubber grips or hard metal grips. The former are good at grabbing fragile objects without breaking them, but will melt if exposed to high temperatures. The latter is much more heat resistant, but not particularly soft to the touch.

Led by an assistant. NUS researcher Prof Chen Ruiqing teamed up with colleagues at Northeast Forestry University in China to combine the best features of both – using wood.

The scientists started with 0.5 millimeter thick strips of Canadian maple and treated them with sodium chloride to remove all lignin, an organic polymer that makes up wood’s cell walls. They then filled the holes left by the missing lignin with a polymer called polypyrrole, which is good at absorbing heat and light.

Next, a layer of nickel-based water vapor absorbing gel is applied to one side of each strip, while a hydrophobic (water-repellent) membrane is applied to the other side. Finally, the strips are placed into heated molds and shaped into curved “fingers”. These fingers are then integrated into a robotic hand, also known as a gripper.

When these appendages are placed in an environment with 95 percent relative humidity, the gel beneath them swells as it absorbs water vapor, causing them to bow outward.

However, when they were placed in an environment heated above 70 ºC (158 ºF), water evaporated from the gel, causing the gel to shrink, which in turn caused the fingers to close inward. Likewise, when the gel is heated by exposure to a strong light source, it shrinks and causes the fingers to close.

assistant. Professor Chen Ruiqing (middle) and team members Mr. Qu Hao (left) and Ms. Bai Lulu (right)
assistant. Professor Chen Ruiqing (middle) and team members Mr. Qu Hao (left) and Ms. Bai Lulu (right)

National University of Singapore

Although these appendages may catch fire Some At one point, they were able to lift 200 grams (7 ounces) at an ambient temperature of 170 ºC (338 ºF) without burning.

“Our wooden robotic gripper can stretch and bend spontaneously in response to humidity, heat, and light stimuli,” Ching said. “It also has good mechanical properties, is capable of complex deformations, operates in a wide temperature range, is cheap to manufacture, and has Biocompatibility. These unique features set it apart from traditional alternatives.”

Of course, one might wonder how to make the fixture open and close on command, rather than just react uncontrollably to its environment.

“By designing some mechanisms and auxiliary equipment, the grasping and releasing of the wooden robotic gripper can be achieved,” Ching told us. “For example, some wires can be added to the wood and the bending actuated by an external voltage, which heats the wires; or a heating plate can be placed near the wood clamp to drive the bending; laser/incandescent lights can also be used to shine the wood surface to generate heat to control bending and grip; we can also spray water around/on the wood to stretch it to release the object.”

The research is described in a paper published in the journal advanced materials.

source: National University of Singapore