A fundamental objective of SRA Developments is to use its technical and marketing expertise to create opportunities from innovation. We are committed to providing solutions to problems that are brought to us by our customers or emerge from our own market experience.

Lateral thinking is the key, backed up by decades of experience of applying ultrasonics to practical situations. Many companies design and build ultrasonic transducers. We do too but our strength lies in our ability to couple the transducer to the workpiece. This could be another piece of production tooling, human tissue or stocking tops.

Everything we develop is patented as a first step since we are expert at recognising genuine novelty. As a result we focus on areas where few or no patents exist. This requires genuinely original ideas but affords strong, defendable IP which, in turn, maximises potential value.

Here are some of the projects we are working on at the moment:

High Intensity Focused Ultrasound - HIFU

This field has been challenging advanced, high frequency ultrasound engineers since the 1950s but a fresh approach to the realities of producing effective focusing systems at a sensible price could open up exciting new possibilities for a range of potential users.

As a result of feasibility study funding (our third SMART award), patents have been applied for which cover the use of a composite metal “concentrator” bonded onto an inexpensive planar piezo device. The key is in the theoretical modelling of the concentrator shape and in achieving critical impedance matching through the device and into the target.

The benefit is in the speed and low cost of designing a custom concentrator for a particular target size, depth and material.

Fabric Welding

This field of technology has been extensively exposed to the benefits of ultrasound over the years, but again applications for the type of welds traditionally achieved in polymer-based fabrics have been limited due to bulk and strength.

With the aid of our second SMART award from the DTI, SRA has developed a new approach to welding polymer fabrics with ultrasound. The key problem of solidified molten conglomerates along the weld line has been eliminated by subjecting the fabric fibres to an intense, inhomogeneous pressure field in air. The obvious step of welding by melting from friction heating has been refined to produce large numbers of “microwelds” along individual fibre bundles where they are compressed momentarily in the pressure field.

The result is a weld with no apparent change in fabric texture but a strength equal to that of the fabric weave. Electron micrographs of polyester at magnifications of 33x and 300x show the fibres stretched out in the weave of the fabric and microwelds between individual fibres. Each fibre comprises chains of polymer molecules.

Contact coupled rotating cam mechanism

In the course of developing surgical instrumentation we have invented a novel way of transferring mechanical force through a flexible linkage. The specific application is to raise and lower a hinged tool mounted at the end of a slim tube or rod so that the tool can apply significant pressure in both of its directions of motion. For a tool mounted on such a rod or tube, actuation by a rotating driver affords a very compact and simple design. Ease and cost effectiveness of assembly are obvious benefits but the fact that coupling between tool and driver is achieved merely by contact pressure allows for easy disassembly and reassembly of the mechanism without breaking and remaking a hard linkage. In addition, the reduction of backlash, which affects position and force control, is highly desirable in precise applications such as surgical instrumentation.

Ceramic cutting

The first technology to be patented by SRA was a dramatically new approach to the literally ancient problem of cutting ceramics. Hard, brittle materials such as ceramic tiles can be cut by sawing them with even harder saw blades. This is dangerous, difficult, messy and expensive.

The common method of cutting many domestic tiles is to score the surface with a hard material and then snap it. In fact tiles have been cut for centuries by hammering the surface to initiate surface cracks which can be “chased” through the tile with successive blows. Scoring the surface has a similar effect with bending of the tile opening up vertical cracks. The finer the hammer tip and the better the control of the blows, the better the finish of the cut. The higher the repetition rate of hammer strikes, the faster the cutting.

SRA was the first to use ultrasound, not only to replicate the tile hammer but enhance the technique to the point where smooth curves can be almost “drawn through” hard tiles.

A handheld device has been developed that adds a high frequency harmonic stress to a steady normal stress against the ceramic surface. While the stress of either on its own does not exceed the cracking stress of the material, the combination does so at the harmonic peaks. The propagation of “microcracks” occurs stepwise through the tile as the harmonic stress peaks. By varying the constant stress, the cutting action can be finely controlled to make the technique suitable for a wide variety of material hardness and surface type.