Sound and heat are the same physics, scaled.
This page derives the bridge from audible acoustic metamaterials to thermal phonons in plain language, with citations to the peer-reviewed record.
Phonons are quantized lattice vibrations.
Electrons and phonons are both quantized carriers. The first runs through silicon and gets steered by engineered heterostructure — that is what a semiconductor is. The second runs through any solid lattice and can be steered by engineered geometry — that is what MetaTherm is.[1]
A semiconductor controls the direction of electron flow. MetaTherm applies the same principle to heat.
The metamaterial composite achieves extreme anisotropy: the thermal conductivity tensor κᵢⱼ takes fundamentally different values along different axes. High resistance inward, higher conductance outward through the wall structure. The wall itself becomes a one-way thermal gate.
The mechanism is geometric. In a periodic elastic structure, the dispersion relation ω(k) develops band gaps — frequency bands in which no propagating modes exist. The center of the gap scales as f ≈ c/2a. Below the lattice constant the wave does not see the structure; above, it Bragg-reflects. The same equations describe an organ pipe, a phononic crystal in silicon, and a tweeter cone.
From millimeters to nanometers.
| Regime | Lattice a | Band f | Application |
|---|---|---|---|
| AUDIBLE | 1 mm – 10 cm | 20 Hz – 20 kHz | Speakers, ANC, absorbers |
| ULTRASONIC | 1 – 500 µm | 0.1 MHz – 1 GHz | Sensors, NDT, RF filters |
| THERMAL | 1 – 100 nm | 0.1 – 10 THz | Heat conduction control |
AMM operates in the audible regime since 2014. The ultrasonic regime is well-characterized in the academic literature. The thermal regime is the frontier — and it is the largest market by orders of magnitude.
Order-of-magnitude reductions in thermal conductivity, in silicon, in 2011.
Hopkins, Reinke, El-Kady et al. (Sandia / UVA) showed that phononic crystal patterning of single-crystal silicon reduces cross-plane thermal conductivity by an order of magnitude.[6] Yang et al. extended this to a 3D nanoscale phononic crystal in pure ²⁸Si, dropping κ from ~50 W/m·K to 4.2 W/m·K.[7] Maldovan derived the thermocrystal framework that explains both.[9] Hu et al. (2020) reviewed the application to electronics packaging — anisotropic heat spreaders, hotspot cloaks, 2.5D thermal management.[2]
Each patent has a thermal cousin.
Each AMM invention has a phonon-domain analogue. The geometric degrees of freedom — channel cross-section, lattice spacing, resonator ratio — translate directly to thermal-domain DOFs: mean-free-path filtering, band-gap center, anisotropy ratio. The portfolio page maps all 13 patents to their published thermal precedents.
- Loudspeaker enclosures→Server-rack acoustic liners
- Sub-wavelength resonator arrays→Phononic-crystal κ-control
- Impedance-matching transducers→Thermal boundary conductance
- Poro-elastic absorbers→Thermal cloaks / nanoporous insulators
- Anisotropic diaphragms→Anisotropic heat spreaders
- Passive metamaterial amplifiers→Heat-flux concentrators