Thermochromic Absorber
A reusable tool for rapid visualisation of the spatial distribution of acoustic intensity. Ideal for use with physiotherapy units
Overview
The Thermochromic Tile, developed by the United Kingdom National Physical Laboratory (London), is a two-layer, pre-cast polyurethane sheet with density and wavespeed similar to that of water. The upper layer is optically and almost acoustically transparent but is designed to trap heat. The lower layer is ultrasonically absorbent and has crystals in it that turn white when exposed to heat. The combination of properties allows the thermochromic tile to be used as a rapid visualisation tool to display the spatial distribution of acoustic intensity for ultrasonic fields incident upon it.
Physical specification
- Appearance of two-layer clear/light-blue polyurethane sheet
- Tile dimensions: 250 mm X 200 mm x 15 mm
- Maximum exposure duration of 5 x frequency (in MHz) over Intensity (in W cm-2)
- There is a resistance to Isopropyl Alcohol (IPA) and trichloroethylene
- It can be affected by ketones (MEK, Acetone) which causes it to swell and dichloromethane which also causes swelling and break down
- Avoid prolonged exposure to Ozone and UV
- The stability of Thermochromic Tiles is very stable due to cross-linked nature of polymer
Acoustical specification
- Suited to frequencies in the 500 kHz to 10 MHz range
- Intensities of 0.5 W cm-2 and upwards