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Yerrapragada K, Yang H, Lee W, Eriten M. Characterization of drying-induced changes in moduli and internal stresses in a constrained gel using laser vibrometry. Soft Matter 2024; 20:813-822. [PMID: 38167912 DOI: 10.1039/d3sm01328f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2024]
Abstract
Hydrogels, water-saturated polymer networks find widespread use in soft robotics, biomedical, pharmaceutical and food industries. Both solid and water constituents of hydrogels are sensitive to external stimuli such as temperature, humidity, osmolarity, and light. For instance, common hydrogels swell or shrink in the presence of chemical potential gradient between the sample and surrounding environment. Corresponding changes in internal water content lead to significant changes in mechanical properties of hydrogels. Besides, internal stresses build up if the gel samples are constrained during swelling or dehydration. In the present research, we utilize modal analyses technique on drying hydrogels to identify dehydration-induced changes in elastic moduli and internal stresses. In particular, natural frequencies and damping ratios of the first two axisymmetric transverse vibration modes are measured on clamped gelatin disks using non-contact laser vibrometry at various water loss states. Experimental modal frequencies are then compared to the predictions of a pre-stressed thick plate model. The evolutions of elastic moduli and internal stresses for water losses up to 80% are identified. The broadband loss capacity of gelatin is also determined from the measured modal damping ratios. Highly transient mechanical response observed on the gelatin disks further demonstrates the need for non-contact and rapid mechanical characterization of hydrogels. As illustrated in this work, vibration and wave-based techniques are promising candidates to fulfill that need.
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Affiliation(s)
- Karthik Yerrapragada
- Department of Mechanical Engineering, University of Wisconsin-Madison, Madison, 53706, WI, USA.
| | - Haocheng Yang
- Department of Mechanical Engineering, University of Wisconsin-Madison, Madison, 53706, WI, USA.
| | - Wonhyeok Lee
- Department of Mechanical Engineering, University of Wisconsin-Madison, Madison, 53706, WI, USA.
| | - Melih Eriten
- Department of Mechanical Engineering, University of Wisconsin-Madison, Madison, 53706, WI, USA.
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Knutsen AK, Vidhate S, McIlvain G, Luster J, Galindo EJ, Johnson CL, Pham DL, Butman JA, Mejia-Alvarez R, Tartis M, Willis AM. Characterization of material properties and deformation in the ANGUS phantom during mild head impacts using MRI. J Mech Behav Biomed Mater 2023; 138:105586. [PMID: 36516544 PMCID: PMC10169236 DOI: 10.1016/j.jmbbm.2022.105586] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2022] [Revised: 09/26/2022] [Accepted: 11/19/2022] [Indexed: 12/12/2022]
Abstract
Traumatic brain injury (TBI) is a major health concern affecting both military and civilian populations. Despite notable advances in TBI research in recent years, there remains a significant gap in linking the impulsive loadings from a blast or a blunt impact to the clinical injury patterns observed in TBI. Synthetic head models or phantoms can be used to establish this link as they can be constructed with geometry, anatomy, and material properties that match the human brain, and can be used as an alternative to animal models. This study presents one such phantom called the Anthropomorphic Neurologic Gyrencephalic Unified Standard (ANGUS) phantom, which is an idealized gyrencephalic brain phantom composed of polyacrylamide gel. Here we mechanically characterized the ANGUS phantom using tagged magnetic resonance imaging (MRI) and magnetic resonance elastography (MRE), and then compared the outcomes to data obtained in healthy volunteers. The direct comparison between the phantom's response and the data from a cohort of in vivo human subjects demonstrate that the ANGUS phantom may be an appropriate model for bulk tissue response and gyral dynamics of the human brain under small amplitude linear impulses. However, the phantom's response differs from that of the in vivo human brain under rotational impacts, suggesting avenues for future improvements to the phantom.
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Affiliation(s)
- Andrew K Knutsen
- Center for Neuroscience and Regenerative Medicine, The Henry M Jackson Foundation for the Advancement of Military Medicine, Bethesda, MD, 20814, USA
| | - Suhas Vidhate
- Radiology and Imaging Sciences, Clinical Center, National Institutes of Health, Bethesda, MD, 20892, USA.
| | - Grace McIlvain
- Department of Biomedical Engineering, University of Delaware, Newark, DE, 19716, USA
| | - Josh Luster
- Department of Neurology, Brooke Army Medical Center, Fort Sam Houston, TX, 78234, USA
| | - Eric J Galindo
- Department of Chemical Engineering, New Mexico Institute of Mining and Technology, Socorro, NM, 87801, USA
| | - Curtis L Johnson
- Department of Biomedical Engineering, University of Delaware, Newark, DE, 19716, USA
| | - Dzung L Pham
- Center for Neuroscience and Regenerative Medicine, The Henry M Jackson Foundation for the Advancement of Military Medicine, Bethesda, MD, 20814, USA
| | - John A Butman
- Radiology and Imaging Sciences, Clinical Center, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Ricardo Mejia-Alvarez
- Department of Mechanical Engineering, Michigan State University, East Lansing, MI, 48824, USA
| | - Michaelann Tartis
- Department of Chemical Engineering, New Mexico Institute of Mining and Technology, Socorro, NM, 87801, USA
| | - Adam M Willis
- Department of Mechanical Engineering, Michigan State University, East Lansing, MI, 48824, USA; 59th Medical Wing, Office of the Chief Scientist, Lackland AFB, TX, 78236, USA
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Triolo E, Khegai O, Ozkaya E, Rossi N, Alipour A, Fleysher L, Balchandani P, Kurt M. Design, Construction, and Implementation of a Magnetic Resonance Elastography Actuator for Research Purposes. Curr Protoc 2022; 2:e379. [PMID: 35286023 PMCID: PMC9517172 DOI: 10.1002/cpz1.379] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Magnetic resonance elastography (MRE) is a technique for determining the mechanical response of soft materials using applied harmonic deformation of the material and a motion-sensitive magnetic resonance imaging sequence. This technique can elucidate significant information about the health and development of human tissue such as liver and brain, and has been used on phantom models (e.g., agar, silicone) to determine their suitability for use as a mechanical surrogate for human tissues in experimental models. The applied harmonic deformation used in MRE is generated by an actuator, transmitted in bursts of a specified duration, and synchronized with the magnetic resonance signal excitation. These actuators are most often a pneumatic design (common for human tissues or phantoms) or a piezoelectric design (common for small animal tissues or phantoms). Here, we describe how to design and assemble both a pneumatic and a piezoelectric MRE actuator for research purposes. For each of these actuator types, we discuss displacement requirements, end-effector options and challenges, electronics and electronic-driving requirements and considerations, and full MRE implementation. We also discuss how to choose the actuator type, size, and power based on the intended material and use. © 2022 Wiley Periodicals LLC. Basic Protocol 1: Design, construction, and implementation of a convertible pneumatic MRE actuator for use with tissues and phantom models Basic Protocol 2: Design, construction, and implementation of a piezoelectric MRE actuator for localized excitation in phantom models.
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Affiliation(s)
- E.R. Triolo
- University of Washington, Dept. of Mechanical Engineering (3900 E Stevens Way NE Seattle, WA 98195)
| | - O. Khegai
- Icahn School of Medicine at Mount Sinai, BioMedical Engineering and Imaging Institute (1470 Madison Ave, New York City, NY 10029)
| | - E. Ozkaya
- Icahn School of Medicine at Mount Sinai, BioMedical Engineering and Imaging Institute (1470 Madison Ave, New York City, NY 10029)
| | - N. Rossi
- Stevens Institute of Technology, Dept. of Mechanical Engineering (1 Castle Point Terrace, Hoboken, NJ 07030)
| | - A. Alipour
- Icahn School of Medicine at Mount Sinai, BioMedical Engineering and Imaging Institute (1470 Madison Ave, New York City, NY 10029)
| | - L. Fleysher
- Icahn School of Medicine at Mount Sinai, BioMedical Engineering and Imaging Institute (1470 Madison Ave, New York City, NY 10029)
| | - P. Balchandani
- Icahn School of Medicine at Mount Sinai, BioMedical Engineering and Imaging Institute (1470 Madison Ave, New York City, NY 10029)
| | - M. Kurt
- University of Washington, Dept. of Mechanical Engineering (3900 E Stevens Way NE Seattle, WA 98195)
- Icahn School of Medicine at Mount Sinai, BioMedical Engineering and Imaging Institute (1470 Madison Ave, New York City, NY 10029)
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