Researchers discover how to stick sensors to skin without adhesive – sciencedaily


Imagine if you could attach something to your skin without the need for glue. A biosensor, a watch, a communication device, a fashion accessory, the possibilities are endless. Thanks to a discovery at Binghamton University, State University of New York, that moment might be closer than you think.

Associate Professor Guy German and Zachary Lipsky, PhD ’21, recently published research in the journal Acta Biomaterialia which explores how human skin can control crack formation and why blood pressure monitors provide inaccurate results when measuring the mechanical properties of biological tissues.

Along the way, Lipsky developed a method to bind human skin to rubbery polymeric materials without an adhesive. Originally, a way to facilitate their experiments, he and German understood that they had made an important discovery.

“Zach came over one day and said, ‘Yeah, I did,'” German said. “I was like, ‘How the hell did you do that? Did you use any glue?’ Because we would also need to take into account the mechanical properties of the glue. And he said, “No, I just glued it.” We looked and we said, has that been done before? Never done, so we’re very happy on that side.

An invention disclosure for the art has been filed which could lead to a patent on what he calls “a very simple technique” that could revolutionize biotechnology.

“I didn’t know we would end up there, but sometimes that’s the way science works,” German said with a laugh.

The study that spawned the discovery, titled “The accuracy of mechanical measurements at the macroscopic scale is limited by the inherent structural heterogeneity of the human stratum corneum,” began with German’s roots in mechanical engineering and his interest in test the validity of Hooke’s law on human skin.

“We figured that if we use these standard testing techniques to measure the mechanical properties of tissues, especially skin tissue, are they reporting the right values? ” he said. “No one has really ever validated it.”

Developed by 17th century British physicist Robert Hooke, the law states that the force required to extend or compress a spring over a distance is proportional to that distance. More generally, researchers can use this law to measure the stiffness of different materials as well as the amount of energy it costs to break them.

“It made me think that in modern times you can measure the stiffness of metals and ceramics. But what about the skin? Said the German. “Metals or ceramics have a fairly uniform composition, but skin and other tissues have a complex and heterogeneous structure with microscopic cells connected by cell-cell junctions. The outer layer of the skin also has a complex topographic network of microchannels, which are visible if you look at the back of your hand. “

He and Lipsky glued skin samples to a piece of polydimethylsiloxane (PDMS), a rubber-like material commonly used in bioengineering and biomedical devices. The samples were then stretched. A modified tensile force microscopy technique was then used to quantify the changes in the mechanical loads imparted by the skin to the adherent substrate.

“As the skin dilated, a little crack would develop, and we can measure the amount of energy needed to make it grow to a certain length,” German said. “Typically, to measure the energy cost of failure in mechanical engineering, you get two handles, you pull, and it splits. You measure force and displacement and quantify energy. But this assumes that the material is homogeneous – the composition is the same everywhere. we found that the cracks in the outer layer of the skin spread in a very, very strange way. “

The cracks propagate along the topographic microchannels. This lengthens the overall path of the crack, increasing the energy it takes to break the tissue. The finding can be extrapolated to explain the behaviors of other human tissues.

“Due to the heterogeneous structure of the skin, it also means that the path to the crack becomes much more random. This is why you get such variability in large-scale blood pressure measurements of the skin,” German said. , “because even though you get the skin from the exact same source at the exact same age, the variability from sample to sample is so high because the crack paths diverge.”

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Material provided by Binghamton University. Original written by Chris Kocher. Note: Content can be changed for style and length.

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