New Method May Lead to Hydrogel Based Soft Robots

North Carolina State University researchers have developed a method that creates devices from hydrogel, a water based poylmer material. The resulting device can be patterned, folded and used to manipulate objects. The research paper, "Reversible Patterning and Actuation of Hydrogels By Electrically Assisted Ionoprinting," is published in the online journal Nature Communications.

Hydrogels are polymers that are highly absorbent that can shrink and expand depending on outside conditions like humidity, pH levels, and temperature. Consumer products use hydrogels in contact lenses for its flexibility, baby diapers for its absorbency, and also in adhesives. Hydrogels are most known for its use as a drug delivery system. Hydrogel based capsules are a popular fixture in pharmacies around the world.

Previously, hydrogels were developed to react a certain way given certain specific conditions. But with the recent discovery, devices can now be developed that can be actively controlled in real time rather than being just reactive. By being able to control the structure and movement of hydrogel, researchers can create devices for use not only for biomedical purposes but also in the field of robotics.

These new devices can be used in the production of soft robots. Soft robots are robots that combine organic chemistry, soft materials science and robotics. These are different from industrial robots in that instead of using gears and motors for movement, soft robots use other means such as chemical reactions or compressed air to move. Soft robots are also made of other materials like rubber and silicon.

Nanogel Based Therapy For Treatment of Systemic Lupus Erythematosus

Nanogels are nano sized particles made up of very absorbent, gelatinous polymers (chemical compounds consisting of repeating structural units) called hydrogels. Nanogels are very small and has pores that can filled with molecules.

These properties make nanogels ideal for medical applications such as a drug delivery or drug containment system. These nanogels can be engineered to break open or rupture to certain environmental or chemical conditions. Controlling where, when, and how much of a drug is to be released results in a more effective and targeted drug delivery.

Recently, scientists are developing nanogels as a delivery system to treat patients suffering from Lupus, an autoimmune disorder that may affect the skin, joints, kidneys, brain, and other organs.

Shear Thinning Hydrogels Developed For Cancer Treatment

Graphic: Christine Daniloff

Gels that can be injected into the body, carrying drugs or cells that regenerate damaged tissue, hold promise for treating many types of disease, including cancer. However, these injectable gels don’t always maintain their solid structure once inside the body.

MIT chemical engineers have now designed an injectable gel that responds to the body’s high temperature by forming a reinforcing network that makes the gel much more durable, allowing it to function over a longer period of time.

The research team, led by Bradley Olsen, an assistant professor of chemical engineering, described the new gels in a recent issue of the journal Advanced Functional Materials. Lead author of the paper is Matthew Glassman, a graduate student in Olsen’s lab. Jacqueline Chan, a former visiting student at MIT, is also an author.

MIT News: Flexible Properties of Hydrogels And Its Practical Applications

Graphic: Christine Daniloff

The flexible properties of hydrogels — highly absorbent, gelatinous polymers that shrink and expand depending on environmental conditions such as humidity, pH and temperature — have made them ideal for applications from contact lenses to baby diapers and adhesives.

In recent years, researchers have investigated hydrogels’ potential in drug delivery, engineering them into drug-carrying vehicles that rupture when exposed to certain environmental stimuli. Such vesicles may slowly release their contents in a controlled fashion; they may even contain more than one type of drug, released at different times or under various conditions.

However, it’s difficult to predict just how hydrogels will rupture, and up until now it’s been difficult to control the shape into which a hydrogel morphs. Nick Fang, an associate professor of mechanical engineering at MIT, says predicting how hydrogels transform could help in the design of more complex and effective drug-delivery systems.

“What kind of shape is more efficient for flowing through the bloodstream and attaching to a cell membrane?” Fang says. “With proper knowledge of how gels swell, we can start to generate patterns at our wish.”

Fang and postdoc Howon Lee, along with colleagues at Arizona State University, are studying the mechanics of shape-shifting hydrogels: looking for relationships between a hydrogel structure’s initial shape, and the medium in which it transforms, in order to predict its final shape. In a paper to appear in Physical Review Letters, the researchers report that they can now create and predict complex shapes — including star-shaped wrinkles and waves — from hydrogels.

The findings may provide an analytical foundation for designing intricate shapes and patterns from hydrogels.

From PowerPoint to 3-D

To create various hydrogel structures, Fang and his collaborators used an experimental setup that Fang helped invent in 2000. In this setup, researchers project PowerPoint slides depicting various shapes onto a beaker of photosensitive hydrogel, causing it to assume the shapes depicted in the slides. Once a hydrogel layer forms, the researchers repeat the process, creating another hydrogel layer atop the first and eventually building up a three-dimensional structure in a process akin to 3-D printing.