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Researchers at Brown University have developed a modular hydrogel assembly using a new dual polymer material that dynamically responds to the environment for a variety of "software robots" and biomedical applications.
Such components made from 3D printers can be bent, twisted or glued together in response to the handling of specific chemicals. In a paper published in the journal Polymer Chemistry, the researchers showed a soft fixture that can drive small objects as needed. They also designed Lego-like hydrogel blocks that can be finely assembled and then tightly sealed together to form a custom microfluidic device for use in "chip lab" systems for drug screening, cell culture and other applications.
Researchers say the key to the functionality of the new material is its dual polymer composition.
Thomas Valentin, a recent Ph.D. student and author of the University of Brown's School of Engineering, said, "In essence, one polymer can provide structural integrity and the other can achieve dynamic behavior, such as bending or self-adhesion. Therefore, two The material that is put together will produce better than the sum of the parts."
When the polymer chains in the hydrogel are tied to each other, the hydrogel solidifies, a process known as cross-linking. There are two types of bonding that integrate crosslinked polymers: covalent bonds and ionic bonds. The covalent bond is quite powerful but irreversible. Once the two chains are covalently linked, the broken chain will be easier than breaking the bond. On the other hand, the ionic bond is not as strong, but it can be reversed. The addition of ions (atoms or molecules with a net positive or negative charge) will result in the formation of bonds, which will result in the separation of bonds.
For this new material, the researchers combined a covalently crosslinked polymer (PEGDA) with another ionically crosslinked polymer (PAA). The strong covalent bond of PEGDA binds the materials together, while the ionic bonds of PAA make them responsive. Placing the material in an ion-rich environment causes the PAA to crosslink, meaning that the material will become harder and shrink. The ions are removed and the material softens and swells as the ionic bond breaks. The same method also allows the material to self-adhesive when needed. Put two separate parts together and add some ions that will be tightly connected together.
This combination of strength and dynamics allows researchers to create soft fixtures. They made the "finger" of each fixture into a pure PEGDA material on one side and a mixture of PEGDA-PAA on one side. The addition of ions causes the PEGDA-PAA surface to shrink and strengthen, bringing the two grips together. The researchers say the mechanism is so powerful that it can lift small objects weighing about 1 gram and be able to "hold" objects against gravity.
Ian Y. Wong, an associate professor and co-author of the papers at Brown University, said, “Everyone is interested in materials that change shape and automatically adapt to different environments, so we show a way to bend and reconfigure itself in response to external stimuli. material."
Researchers also said that the more direct application of the material may be in the field of microfluidics.
Hydrogels are a popular material for microfluidic devices, especially in biomedical testing applications. They are as soft and elastic as human tissue and are usually non-toxic. The problem is that it is often difficult to make complex microchannels and chambers with hydrogels in a microfluidic device.
But this new material, and the Lego building concept it covers, offers a potential solution. 3D printing allows complex microfluidic structures to be incorporated into each small block. You can then use the socket configuration to assemble these small pieces more like real Lego bricks. Watertight seams can be formed by adding ions to the assembled pieces.
Valentin pointed out that “modular LEGO bricks are very interesting because we can create prefabricated toolboxes for microfluidic devices. You can use different microfluidic structures to retain various preset components at any time, then choose to make custom microfluidic chains. The parts needed for the road. Then assemble them."
Researchers say that storing these small pieces for long periods of time before use is not a problem.
Eric DuBois, an undergraduate and co-author of Brown University, said, "The samples used in this study are some three months or four months ago, so we think these materials will remain available for a long time."
Researchers say they will work on the material and may adjust the properties of the polymer for greater durability and functionality in the future.
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First of all, Easter eggs are one of the indispensable decorations. We use dyes of various colors to paint eggs with bright colors, or paint elaborate patterns on the shells to make them little works of art. These eggs can be placed on the dining table or hung on the Easter tree, bringing joy and surprise to people.
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