Cleaning dirty surfaces is a tedious, labour-intensive task. Dirt often adheres to a surface so strongly that detergents cannot simply float it away. It has to be dislodged by mechanical scrubbing. One neat way out is the ultrasonic cleaning bath, whose detergent solution is agitated by a source of high-frequency sound. Daedalus is now extending the idea.

DREADCO engineers are fitting a standard high-pressure water-hose with a powerful piezoelectric ultrasonic generator. It launches a beam of ultrasound along the emerging water jet. Ultrasound is transmitted very efficiently by water; it can travel many tens of metres with little loss. Furthermore, the strong refractive mismatch between air and water will prevent the sound escaping from the jet and spreading wastefully out into the air. Nearly all the ultrasonic energy will hit the target, and will dislodge the dirt with great vigour. The water will then wash it away. Even if the jet breaks up into droplets during its journey, its scouring action will not be lost, for water droplets resonate strongly at ultrasonic frequencies (which is why bats don't like fog). The rapidly vibrating droplets will still deliver their ultrasonic energy to the target surface.

The DREADCO ‘Ultrajet’ cleaning hose will abolish many tedious jobs, notably external window-cleaning and the renovation of grimy public buildings and monuments. Scaffolding and suspended cradles, buckets and brushes and chamois leather, will no longer be needed; a simple high-velocity water-jet aimed from the ground will do the job. A thin jet of modest flow rate should be quite adequate, especially if a suitable detergent is dissolved in the water. Urban grime, peeling paint, pigeon-droppings and maybe even graffiti will be speedily and efficiently stripped from our urban eyesores. On a smaller scale, bus and train cleaning and the humble car-wash itself will be splendidly speeded and transformed.

Domestic applications are also possible. Sadly, the Ultrajet will not replace the vacuum-cleaner or the duster for internal household maintenance. But it could powerfully upgrade the action of the washing machine and the bathroom shower. An ultrasonically assisted shower would clean and exfoliate the user with a bracing ultrasonic massage. And DREADCO's Ultrajet toothbrush will vigorously dislodge dental grime and plaque, and give an unprecedented tingling-fresh sensation into the bargain.