i Research: Chiara Daraio

Daraio Group Research

Daraio's lab is primarily interested in:

  1. Developing a physical understanding of how stress waves propagate in nonlinear, ordered and disordered solid media at length scales ranging from nanometers to meters.
  2. Exploiting this understanding for the creation of new materials and devices for engineering applications ranging from optomechanics to shock absorption.

To achieve these goals, our research takes advantage of nonlinearities in local material interactions (e.g., Hertzian contact interactions between particles or nonlinear interactions between nanostructures) to create novel systems and new materials with unprecedented global properties. These materials are composite systems in which typically basis elements that interact nonlinearly are arranged in well-defined geometries, such that the aggregate system as a whole exhibits properties that are not usually found in natural systems and can be exploited in engineering applications.

Our work is primarily experimental, but it is informed by numerical and analytical studies, which serve as a guide in metamaterial construction and validation of their properties.

Resources from our research lab can be accessed at our GitHub page.

Composite metamaterials for vibration absorption

Composite metamaterials for vibration absorption imageIn this project, we are designing composite metamaterials based on coupling a periodic architected lattice with local resonances. These meta-structures can reflect and prohibit the propagation of structural vibrations. We rely on recent advances in additive manufacturing to 3D print composite materials that combine periodically embedded metal resonators within a periodic lattice structure, functioning as a support matrix. The coupling of structural modes of this lattice and the local resonators enables the formation of low and wide band gaps. This work opens up new possibilities for designing and fabricating low and wide band gap metamaterials with potential applications ranging from robust and lightweight acoustic absorbers in buildings, vibration isolation in MEMS devices, and passive frequency filters for ultrasonic transducers.

Currently: Dr. Katie Matlack

Micro-structured phononic crystals

We study experimentally and numerically the dynamics of microlattices fabricated using 3D-photolithography. The microstructure design is motivated by peculiar molecular structures, like semiconductor superlattices or Perovskites. These structures show highly altered phonon propagation properties. As the main differnence between phonons and elastic waves is their characteristic frequency, we are able to use the specific molecular geometries and scale them up to alter to elastic wave propagation. With the incredible design space that the fabrication process offers we are able to explore possible application in ultrasonic imaging, MEMS/NEMS protection and shock absorption.

Dynamic properties of micro- and nanoscale structural metamaterials

Currently: Sebastian Krödel

Microscale Nonlinear Crystals

Microscale Nonlinear Crystals imageWe conduct experiments on the dynamic interaction in micro-particles systems (10-300 µm), including the dynamics collisions between micro-particles, the adhesive force and the local potential of different particles-surface contacts and mechanical solitary wave in granular systems at micro-scale.

Currently: Wei-Hsun Lin

Nonlinear dynamics in granular materials

Tunable Acoustic Diodes image

We examine the nonlinear dynamics and the effects of finite size in granular crystals. Using phenomena from bifurcations, stability, and spectral theory, we design structures for applications, including amplitude dependent damping, filtering, and energy harvesting.

Currently: Joseph Lydon, Marc Serra Garcia, Paul Anzel

Recent publications:
"Frequency Bands of Strongly Nonlinear Homogeneous Granular Crystals" (link)
"Dark Breathers in Granular Crystals" (link)

Controlling wave propagation with local resonances

Local resonances image

We study the effect of local resonances on wave propagation in acoustic metamaterials. Our research ranges from macroscale resonant granular crystals for vibration mitigation to microarrays of resonators to control surface acoustic waves.

Currently: Luca Bonanomi, Marc Serra Garcia

Recent publications:
"Interaction of Traveling Waves with Mass-With-Mass Defects within a Hertzian Chain" (link)
"Defect Modes in One-Dimensional Granular Crystals" (link)

Materials Enhanced with Negative Stiffness and Mass Density Phase

Electromagnetic Negative Index Metamaterials (NIM) have drastically improved properties and can be designed for applications such as sub-wavelength optical focusing in the form of a superlens, invisibility cloaking at certain frequencies and superior filtering, among others. Negative stiffness and negative mass are the acoustic analogues to the negative permeability and permittivity seen in the left handed NIMs. The research effort here would be to use negative stiffness and negative mass properties to bring these phenomena to the acoustic paradigm and use them in the creation of superior acoustic metamaterials.

The instabilities generated by the presence of negative stiffness phases create large variations in displacements with minimal forcing requirements thereby causing different regimes in wave propagation. The tunability of these structures can lead to the propagation of phonons, weakly nonlinear and highly nonlinear solitary waves. Current research is focused on characterizing the wave propagation properties of bistable springs with negative stiffness phases from a computational and theoretical perspective. Experimental investigation would follow in order to support the theoretical findings.

This work is a collaborative research effort with the Kochmann Research Group at the Graduate Aerospace Laboratories of the California Institute of Technology (GALCIT), Caltech, USA.

Currently: Neel Nadkarni

Acoustic Metamaterials

Acoustic MetamaterialsUsing theory, numerical simulations and experiments, we study the propagation of acoustic waves in media with hollow channels. Coiling the channels, we are able to tune the speed of traveling waves. Such structures can be used to design acoustic lenses, thin absorbing materials or directive sources.

Currently: Miguel Moleron

Microscale nonlinear systems

Acoustic MetamaterialsWe explore dynamic phenomena in micro-scale granular crystals. We are trying to fabricate our systems with the aid of micro-fabrication techniques, and to excite and to measure on the chip level using MEMS techniques such as piezoelectric or electrostatic actuations and detections.

Currently: Jinwoong Cha

Advanced Structured Scaffolds

Polymer ScaffoldWe fabricated periodic lattice structures in the micro- and nanoscale using photolithography. The basic lattice will be functionalized with a variety of different coatings. We study their dynamic behavior and the potential integration into biomimetic propulsion systems.

Currently: Jan Rys

Contact Laws for Elastic-Plastic Spheres at High Strain-rates

Contact Laws for Elastic-Plastic Spheres at High Strain-ratesPrevious research in the Hertzian system have relied on the assumption that the plastic, i.e. permanent deformations are negligible and that the particles fully rebound after compression. However, in reality, plasticity occurs at relatively small forces and therefore it must be considered in many real-world applications of these materials. The goal of this project is to model the effect of the permanent deformations of the particles on the properties of wave propagation.

This research is being carried out in collaboration with Prof. Guruswami Ravichandran at Caltech.

Currently: Hayden Burgoyne