I. Novel Solitonic Waveguides Based on Granular Phononic Crystals

(Colloborator: Dr. Michael Sutton, Univ. of South Carolina, Sponsored by NSF)

The objective of this research is to simulate and measure the formation of acoustic solitons in two-dimensional granular waveguides. We will design and fabricate hexagonally packed granular lattices – defined as granular phononic crystals – contained in a narrow channel. We will unveil unique soliton formation and transmission mechanism in the assembled granular architectures. The fundamental understanding of soliton propagation will enable a new class of waveguides that can filter, delay, and redirect acoustic solitons in a controllable and efficient manner. We will achieve this research goal by developing an advanced discrete element model (DEM) and a novel digital image correlation (DIC) technique. Based on molecular dynamics techniques, the DEM will simulate the propagation of solitons under the full consideration of axial and rotational dynamics of tightly-packed, frictional particles. We will verify the numerical simulation results by the DIC techniques that measure extremely small particle displacements at high sampling rates.

II. Lightweight and Tunable Composite Structures Using Structural Materials

(Collaborators: Dr. Chiara Daraio, Caltech & Dr. Duc Ngo, Eastern International University, Vietnam)

The task objective of the proposed research is to develop a concept demonstrator of tunable and lightweight composite material systems that suppress acoustic noises in a controllable manner. We will achieve this by employing novel structural materials (e.g., granular phononic crystals) that are composed of strategically arranged mechanical components. These material systems can suppress wide-band, low-frequency acoustic noises by leveraging the presence of tunable frequency bandgaps inherent in these periodic structural materials. If successful, this tunable and lightweight composite system can be employed in the engine mount or fuselage structures to construct quiet and eco-friendly aircrafts that block acoustic noises in a passive and efficient way.

III. Self-sensing Artificial Skin Structure Based on Nonlinear Mechanical Network

(Collaborator: Dr. Amanda Schrand, Air Force Research Laboratory, Eglin, FL)

Throughout nature, highly nonlinear waves in the form of solitons have been observed in nerves and biomembranes for the efficient transmission of electrochemical signals. Inspired by such nonlinear mechanisms in biological systems, we propose to design and fabricate an artificial nervous system (ANS) using granular networks that form and propagate acoustic solitons. This novel system will discern vibrations, impacts, and other aspects of the environment by leveraging unique physical properties of acoustic solitons. This operation is analogous to signal transduction by neurons in biological systems or electromagnetic soliton transmission in optical communications. The robustness and sensitivity of solitons make them extremely useful as information carriers in this application. At the micro-scale, this structure has the potential as a component of touch-sensitive transducers such as tactile sensors. The granular layers can be also constructed to mitigate impact, creating a novel defense structure that can protect and monitor the host media in real time.

Previous Projects

Tunable acoustic structures
(@ Caltech sponsored by DARPA)

Numerical simulations of nonlinear waves
(@ Caltech sponsored by NSF and ONR)

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