Osama R Bilal | Swiss Federal Institute of Technology (ETH) (original) (raw)

Papers by Osama R Bilal

Applied Physics Letters

Through a combination of analytical, numerical, and experimental methods, we study a three-dimens... more Through a combination of analytical, numerical, and experimental methods, we study a three-dimensional metamaterial with the ability to attenuate both airborne sound and mechanical vibrations, simultaneously, and in all directions. In addition, due to the auxetic nature of the design (i.e., having a negative Poisson's ratio), the metamaterial can shrink (or expand) in a relatively uniform manner, without buckling. We utilize an external load to cause a systematic shape change in the metamaterial and tune the attenuation frequency bands. The presented design principles can be utilized in many applications related to acoustic and elastic wave manipulation as well as acoustic devices.

Physical Review Applied, 2022

Extreme Mechanics Letters, 2022

Journal of Applied Physics, 2016

Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2015

The interaction between a fluid and a solid surface in relative motion represents a dynamical pro... more The interaction between a fluid and a solid surface in relative motion represents a dynamical process that is central to the problem of laminar-to-turbulent transition (and consequent drag increase) for air, sea and land vehicles, as well as long-range pipelines. This problem may in principle be alleviated via a control stimulus designed to impede the generation and growth of instabilities inherent in the flow. Here, we show that phonon motion underneath a surface may be tuned to passively generate a spatio-temporal elastic deformation profile at the surface that counters these instabilities. We theoretically demonstrate this phenomenon and the underlying mechanism of frequency-dependent destructive interference of the unstable flow waves. The converse process of flow destabilization is illustrated as well. This approach provides a condensed-matter physics treatment to fluid–structure interaction and a new paradigm for flow control.

Advanced Functional Materials, 2022

Band structure calculation provides a basis for the study of thermal, optical and magnetic proper... more Band structure calculation provides a basis for the study of thermal, optical and magnetic properties of crystals. The reduced Bloch mode expansion (RBME) method is a model reduction method in which a selected set of Bloch eigenvectors within the irreducible Brillouin zone at high symmetry points are used to expand the unit cell problem at hand. In this method, a major reduction in computational cost is achieved with minimum loss of accuracy. The method applies to both classical and ab inito band structure calculations of periodic media, and to any type of wave propagation problem: phononic, photonic, electronic, etc. In this work, the applicability of RBME in calculating the three-dimensional (3D) electronic band structure for crystal structures with different symmetries is demonstrated. Using the Kronig-Penney fixed potential, a highsymmetry cubic model and a low-symmetry triclinic model are considered. For both cases, the energy (eigenvalues) and wave functions (eigenvectors) dem...

Bulletin of the American Physical Society, 2020

Bulletin of the American Physical Society, 2017

arXiv: Applied Physics, 2020

Phononic metamaterials enabled the realization of many acoustic components analogous to their ele... more Phononic metamaterials enabled the realization of many acoustic components analogous to their electronic counterparts, such as transistors, logic gates and calculators. A key component among these is the demultiplexer, a device that receives multiple signals and sorts them based on their frequencies into separate channels. Previous experimental realizations of acoustic and elastic multiplexers have employed plates with pillars or holes to demultiplex frequencies. However, existing realizations are confined to two-dimensions, which can limit potential acoustic or elastic circuit design. Here we show the first experimental realization of a three-dimensional, four channel phononic demultiplexer. Our design methodology is based on bundles of pass-bands within a large band gap that can easily be tuned for multi-channel frequency demultiplexing. The proposed design can be utilized in acoustic and elastic information processing, nondestructive evaluation and communication applications amon...

Bulletin of the American Physical Society, 2015

2010 The 7th International Conference on Informatics and Systems (INFOS), 2010

Topological distribution of dielectric materials within a unit cell has a significant effect on h... more Topological distribution of dielectric materials within a unit cell has a significant effect on how waves propagate through the material. Through topology optimization, the configuration of a periodic material's unit cell can be designed to specification. In many applications, it is desired to have a unit cell with as large a band gap as possible. In this paper we use Genetic Algorithms (GA) to optimize the design of unit cells in order to maximize the material's band gap. We explore a number of approaches for the parametrization of the unit unit cell design. All of these approaches exploit different symmetries on the unit cell. We have examined transverse-electric and transverse-magnetic wave propagation with the aim to maximize the first band gap. The results show that the specialized GA operators have a dramatic effect on optimization performance. The results also imply that the type of symmetry constraint has a significant effect on the unit cell design and band gap size.

Bulletin of the American Physical Society, 2016

In most macro-scale robotics systems , propulsion and controls are enabled through a physical tet... more In most macro-scale robotics systems , propulsion and controls are enabled through a physical tether or complex on-board electronics and batteries. A tether simplifies the design process but limits the range of motion of the robot, while on-board controls and power supplies are heavy and complicate the design process. Here we present a simple design principle for an untethered, entirely soft, swimming robot with the ability to achieve preprogrammed, directional propulsion without a battery or on-board electronics. Locomotion is achieved by employing actuators that harness the large displacements of bistable elements, triggered by surrounding temperature changes. Powered by shape memory polymer (SMP) muscles, the bistable elements in turn actuates the robot's fins. Our robots are fabricated entirely using a commercially available 3D printer with no post-processing. As a proof-of-concept, we demonstrate the ability to program a vessel, which can autonomously deliver a cargo and na...

Advanced Materials, Nov 1, 2017

Programmable materials hold great potential for many applications such as deployable structures, ... more Programmable materials hold great potential for many applications such as deployable structures, soft robotics, and wave control, however, the presence of instability and disorder might hinder their utilization. Through a combination of analytical, numerical, and experimental analyses, we harness the interplay between instabilities, geometric frustration, and mechanical deformations to control the propagation of sound waves within self-assembled soft materials. We consider levitated magnetic disks confined by a magnetic boundary inplane. The assemblies can be either ordered or disordered depending on the intrinsic disk symmetry. By applying an external load to the assembly, we observe the nucleation and propagation of different topological defects within the lattices. In the presence of instabilities, the defect propagation gives rise to time-independent localized transition waves. Surprisingly, in the presence of frustration, the applied load briefly introduces deformationinduced o...