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  5. Sound Engineering: The mystery of forces in living matter

Sound Engineering: The mystery of forces in living matter

The University of Wisconsin-Madison recently welcomed Michael Murrell to both its biomedical engineering department and its materials science and engineering department. Specializing in how living cells and tissues produce mechanical forces, Murrell’s lab—the Laboratory of Living Matter—hopes to answer some fundamental questions about how living matter moves, reproduces and changes shape.

John Steeno: All cells and tissues produce mechanical forces to move, reproduce, or change their shape. But even though this force production is a fundamental part of the cell and tissue life cycle, so much is unknown about the process of producing these forces. The Laboratory of Living Matter, a research group headed by assistant professor Michael Murrell, aims to change that.

Michael Murrell: Yet, we don’t really have a great understanding about how it is that they produce these forces. We kind of have a good impression of what the molecular players are, what the molecules are, but how they interact to generate forces, how the physical properties of cells allow them to transmit these forces over long distances, over long times—all of this is pretty unknown. 

John Steeno: Murrell, who has joint appointments in the UW-Madison Biomedical Engineering and the Materials Science and Engineering departments, says his laboratory is approaching these mysteries from two directions. The first approach is to study the living cells and tissues themselves. The other approach is to create biomimetic cells, which are simplified mechanical models of cells.

Michael Murrell: The basic idea is: get them to do something that a cell does. Then, you can explore the fundamental mechanism for how that happened, because you added the components yourself, and you put them in a particular stoichiometric ratio, you added the biochemical conditions. So you can modulate it to understand how the variables influence that behavior. Because there aren’t 20,000 things: there are five. So the overall point is to reproduce the behavior and then go back to the components inside and perturb them to understand what each of their roles are.

John Steeno: Murrell says biomimetic cells are helpful in research because living cells can obscure the production of the forces that internally affect cells.

Michael Murrell: One of the main problems with working directly with cells is that, for example, if you wanted to mechanically probe a cell, you wanted to poke it. Well, you could do that, and you might be able to measure a strain, but then when you do that the cell is going to mount a response to that, because it sensed it. And then it says there’s a problem here, and so it changes the entire biochemical landscape of the cell because it thinks it’s under threat. And so it can interfere with the direct understanding of the mechanical properties of this cell because it’s confounded in there with its stress response, or with its general metabolism.

And so the point is, we take those mechanical elements out of the cell so that they’re not regulated by the cell anymore, and there’s no stress response; there’s no metabolism. And so it’s purely a mechanical thing that remains.

John Steeno: To learn more about Michael Murrell and the Laboratory of Living Matter, visit

John Steeno