This scientific thrust will explore analytical, numerical, and experimental studies of phononic materials with building blocks incorporating multistability, non-linear or topological elements as a primary architectural feature, and a secondary building block with non-linear or structural features. 

Project Themes:

• Non-linear wave propagation and interactions in phononic materials featuring multiple types of non-linearities – geometric, material, and contact;

• Architectures leveraging topological and structural elements (e.g., kinematic amplification, defects) to create highly localized bandgap resonances relevant for applications, e.g., energy harvesting, passive flow control;

• Combining multistability and topology to realize reconfigurable topological wave-guides, mechanical logic and cloaking devices.

This scientific thrust will explore analytical, numerical, and experimental studies of materials that combine stimuli-responsive elements with secondary features, e.g., geometric and material non-linearity, and study the emergent material behavior.

Project Themes:

• Model and identify material behavior relevant for specific robotic functions, e.g., autonomous actuators replicating sensory reflex actions of robotic limbs, effective energy absorption and cloaking mechanisms to safeguard electronic components constituting the robotic CNS from adverse external loads;

• Develop functional smart materials by translating beneficial material functionalities at smaller scales;

• Perform analytical, numerical and experimental validations of these material designs using high-fidelity simulations, fabrication and testing processes

• Proposed an alternate lens to view phononic materials (PMs) in terms of behavioral parameters such as truncation resonance frequency and amplitude envelope as opposed to the traditional structural parameters such as mass and stiffness

• Developed a systematic framework linking PM behavioral parameters to relevant flow quantities the coupled frequency and the lift force

•  High-fidelity fluid-structure interaction (FSI) results indicate distinct vortex-shedding behavior when tuning the behavioral parameters

V. Ramakrishnan, A. M. Burgos, S. Park, K. H. Matlack, A. Goza, "A Framework to Systematically Study the Fluid-Structure Interaction of Phononic Materials with Aerodynamic Flows", J. Fluids Struct., 145, 104569 (2026) DOI: https://doi.org/10.1016/j.jfluidstructs.2026.104569 

• Translated a reduced order spring-mass model of a monoatomic phononic crystal into a 3D printed experimental specimen for FSI with T-S Waves

• A pass band resonance in coordination with a MIMO-inspired configuration is leveraged to generate the desirable force-displacement phase difference at the FSI interfaces

• LDV and LDA measurements from the transonic wind tunnel tests of FSI with a phononic material were performed and analyzed

V. Ramakrishnan and M. J. Frazier, "Multistable metamaterial on elastic foundation enables tunable morphology for elastic wave control", J. Appl. Phys., 127, 225104 (2020) DOI: https://doi.org/10.1063/1.5145324 

• A spatio-temporal potential modulation is used to control a transition wave (kink soliton)

• A transition wave can be effectively modeled as a Newtonian particle provided it approximately retains a permanent profile

• Spatio-temporal modulations give rise to two distinct regimes of propagation depending on the modulation speed

V. Ramakrishnan and M. J. Frazier, "Transition waves in multi-stable metamaterials with space-time modulated potentials", Appl. Phys. Lett., 117, 151901 (2020) DOI: https://doi.org/10.1063/5.0023472 

• Experimentally demonstrated the non-equilibrium response of an active architected material, i.e., Turing patterns in the displacement field

• Verified experimental data with analytical and numerical data

• The elastodynamic model closely resembles the phenomenological reaction-diffusion models developed for self-organization in biological and chemical systems

• Architected material provides a template to engineer non-equilibrium effects on a customizable platform

V. Ramakrishnan and M. J. Frazier, "Pattern Formation in Non-Equilibrium Architected Materials", Adv. Mater. Tech., 11(10), e01325 (2026) DOI: https://doi.org/10.1002/admt.202501325