An official website of the United States government
Abstract Brillouin light scattering and elastodynamic theory are concurrently used to determine and interpret the hypersonic phonon dispersion relations in brush particle solids as a function of the grafting density with perspectives in optomechanics, heat management, and materials metrology. In the limit of sparse grafting density, the phonon dispersion relations bear similarity to polymer‐embedded colloidal assembly structures in which phonon dispersion can be rationalized on the basis of perfect boundary conditions, i.e., isotropic stiffness transitions across the particle interface. In contrast, for dense brush assemblies, more complex dispersion characteristics are observed that imply anisotropic stiffness transition across the particle/polymer interface. This provides direct experimental validation of phonon propagation changes associated with chain conformational transitions in dense particle brush materials. A scaling relation between interface tangential stiffness and crowding of polymer tethers is derived that provides a guideline for chemists to design brush particle materials with tailored phononic dispersion characteristics. The results emphasize the role of interfaces in composite materials systems. Given the fundamental relevance of phonon dispersion to material properties such as thermal transport or mechanical properties, it is also envisioned that the results will spur the development of novel functional hybrid materials.
more »
« less
Experimental realization of an additively manufactured monatomic lattice for studying wave propagation
Increasing interest in wave propagation in phononic systems and metamaterials motivates the development of experimental designs, measurement techniques, and fabrication methods for use in basic research and classroom demonstrations. The simplest phononic system, the monatomic chain, exhibits rich physics such as dispersion and frequency-domain filtering. However, a limited number of experimental studies showcase monatomic chains for macroscale observation of phonons. Herein, we discuss the design, fabrication, and testing of monatomic lattices as enabled by three-dimensional (3D) printing. Using this widely available technology, we provide design guidelines for realization of a monatomic chain composed of 3D printed serpentine springs and press-fitted cylindrical masses. We also present measurement techniques that record propagating waves and algorithms for the experimental determination of dispersion behavior.
more »
« less
- Award ID(s):
- 1929849
- PAR ID:
- 10440218
- Publisher / Repository:
- American Association of Physics Teachers (AAPT)
- Date Published:
- Journal Name:
- American Journal of Physics
- Volume:
- 91
- Issue:
- 1
- ISSN:
- 0002-9505
- Page Range / eLocation ID:
- p. 56-63
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Phononic waveguides (PnWGs) are devices with rationally designed periodic structures to manipulate mechanical oscillations and to engineer and control the propagation of acoustic waves, thus allowing for frequency and band selection of wave transmission and routing, promising for both classical and quantum transduction on chip-scale platforms with various constituent materials of interest. They can be incorporated into both electromechanical and optomechanical signal transduction schemes. Here, we present an overview of emerging micro/nanoscale PnWGs and offer perspectives for future. We evaluate the typical structural designs, frequency scaling, and phononic band structures of the PnWGs. Material choices, fabrication techniques, and characterization schemes are discussed based on different PnWG designs. For classical transduction schemes, an all-phononic integrated circuit perspective is proposed. Toward emerging quantum applications, the potential of utilizing PnWGs as universal interfaces and transduction channels has been examined. We envision PnWGs with extraordinary propagation properties, such as nonreciprocity and active tunability, can be realized with unconventional design strategies (e.g., inverse design) and advanced materials (e.g., van der Waals layered crystals), opening opportunities in both classical and quantum signal transduction schemes.more » « less
-
Abstract Phononic crystals exhibit Bragg bandgaps, frequency regions within which wave propagation is forbidden. In solid continua, bandgaps are the outcome of destructive interferences resulting from periodically alternating material layers. Under certain conditions, natural frequencies emerge within these bandgaps in the form of high‐amplitude localized vibrations near a structural boundary, referred to as truncation resonances. In this paper, the vibrational spectrum of finite phononic crystals which take the form of a one‐dimensional rod is investigated and the factors that contribute to the origination of truncation resonances are explained. By identifying a unit cell symmetry parameter, a family of finite phononic rods, which share the same dispersion relation, yet distinct truncated forms, is defined. A transfer matrix method is utilized to derive closed‐form expressions of the characteristic equations governing the natural frequencies of the finite system and decipher the truncation resonances emerging across different boundary conditions. The analysis establishes concrete connections between the localized vibrations associated with a truncation resonance, boundary conditions, and the overall configuration of the truncated chain as dictated by unit cell choice. The study provides tools to predict, tune, and selectively design truncation resonances, to meet the demands of various applications that require and uniquely benefit from such truncation resonances.more » « less
-
Abstract A modified incremental harmonic balance (IHB) method is used to determine periodic solutions of wave propagation in discrete, strongly nonlinear, periodic structures, and solutions are found to be in a two-dimensional hyperplane. A novel method based on the Hill’s method is developed to analyze stability and bifurcations of periodic solutions. A simplified model of wave propagation in a strongly nonlinear monatomic chain is examined in detail. The study reveals the amplitude-dependent property of nonlinear wave propagation in the structure and relationships among the frequency, the amplitude, the propagation constant, and the nonlinear stiffness. Numerous bifurcations are identified for the strongly nonlinear chain. Attenuation zones for wave propagation that are determined using an analysis of results from the modified IHB method and directly using the modified IHB method are in excellent agreement. Two frequency formulae for weakly and strongly nonlinear monatomic chains are obtained by a fitting method for results from the modified IHB method, and the one for a weakly nonlinear monatomic chain is consistent with the result from a perturbation method in the literature.more » « less
-
Three-dimensional (3D) printing has emerged as a transformative technology for fabricating complex microfluidic devices, enabling features that were previously unattainable with traditional layer-by-layer soft lithography. One key challenge in advancing 3D-printed microfluidics is the integration of functional microvalves across multiple spatial orientations. This study explores the design, simulation, and experimental realization of novel microvalve configurations to overcome the limitations of conventional, single-plane valves. We hypothesize that non-traditional valve orientations, such as those with vertically printed membranes or perpendicular control channels, present unique fabrication and operational challenges, including membrane delamination and stress-induced failure. To address these issues, we developed optimized geometries and fabrication techniques, supported by computational fluid dynamics (CFD) simulations to predict and mitigate stress concentrations. Our results demonstrate successful implementation of previously unreported valve configurations, validated through pressure testing and flow control experiments. These advancements expand the versatility of 3D-printed microfluidic systems, paving the way for more robust and adaptable devices in biomedical, chemical, and environmental applications.more » « less
