skip to main content

Mechanical and Civil Engineering Seminar

Thursday, May 5, 2022
11:00am to 12:00pm
Add to Cal
Gates-Thomas 135
Adaptive and Sensory Machines: From Active Foam to Swimming Rheometers
Laurel Kroo, Mechanical Engineering, Stanford University,

Mechanical and Civil Engineering Seminar Series

Title: Adaptive and Sensory Machines: From Active Foam to Swimming Rheometers

Abstract: In this talk, I will discuss passive adaptation and sensing in fully-synthetic engineered systems, with two specific examples [1] [2]. First, in the context of studying the self-assembly of programmable soft matter, I discuss the response of 2D air-liquid foam to cyclical inflation and deflation of an embedded "active" bubble. Experimental and numerical results suggest that such volume oscillations can be used to train foam to achieve local structural properties, communicate long-range mechanical signals through the CW/CCW motion of vertex trajectories, and may be used to actively probe properties of the surrounding network structure. I will also discuss the statistical influence of microstructural yielding events ("T1 transitions") within the material, and the role of disorder on the mechanical response.

In the next example, I will discuss how an untethered robot is capable of self-propulsion at low Reynolds number only when submerged in an elastic fluid (studied in collaboration with Prof. Eric Shaqfeh's group). This robot consists of two counter-rotating rotationally-symmetric objects, and propels itself in the direction of the larger "head" object. By controlling the relative rotation rate of this device while recording motility, the robot acts as rheological sensor of the surrounding fluid, with remarkable sensitivity. I will discuss our experimental discovery of a non-inertial, viscoelastic jet structure responsible for propulsion, and the specific rheological properties that can be inferred by observation of the device.

Fundamentally, these examples demonstrate how adaptive and sensory machines can be used in engineering to enable exceptional redundancy and robustness in real-world environments.

Bio: Laurel A. Kroo recently defended her PhD in Mechanical Engineering at Stanford University, under the mentorship of Professor Manu Prakash. She received a master's degree in Mechanical Engineering from Stanford in 2017 and a bachelor's degree in Mechanical Engineering from Franklin W. Olin College of Engineering in 2014. Her interests center on the intersection between robotics and soft condensed matter physics. Specifically, her primary research is focused on topics related to self-organization under confinement, distributed control in soft materials, and actuation/sensing in non-newtonian fluids. Her former professional affiliations include employment at Apple, NASA Ames Research Center and a number of San Francisco Bay-Area hardware start-ups. She is a Hertz Fellowship finalist and a recipient of the National Science Foundation's Graduate Research Fellowship.

NOTE: At this time, in-person Mechanical and Civil Engineering Lectures are open to all Caltech students/staff/faculty/visitors with a valid Caltech ID.

As part of the Young Investigators Lecture Series, this seminar will be presented on Zoom.

Please click on the link below to join the webinar:

For more information, please contact Stacie Takase by phone at (626) 395-3389 or by email at [email protected] or visit