1. Aims & Objectives
DeMontfort University (DMU) are currently engaged in a collaborative research programme with Harvard
Medical School to develop instrumentation that is capable of measuring the visco-elastic properties of the
human vocal fold.
We aim to
 Develop techniques to measure the visco-elastic properties of ex-vivo samples
 Gain a greater understanding of vocal fold mechanics by the generation of 2D maps of these visco-elastic
 Investigate a range of sensors that can make similar readings in-vivo
 Design and develop a clinical tool that can be used in-vivo
A greater understanding of vocal fold mechanics will greatly aid the diagnosis and treatment of patients with
impaired speech. The availability of a compact and robust clinical tool that can be used to probe and measure
the vocal fold in-vivo will aid clinicians to identify pathology, and more precisely locate the area of damage,
thus aiding diagnosis.
Our research programme’s primary purpose is to identify new sensors that have a medical application. The
team has already identified Surface Acoustic Waves (SAW) sensor technology as one such device, but other
devices may yet be identified. The outcome will be a new medical device for use with the vocal fold, but
may also be suitable for other tissues.
2. Research Programme
The Linear Skin Rheometer (LSR)
The LSR is designed to carry out in-vivo measurement of the elastic
and viscous properties of skin. By their very nature such
measurements are difficult to perform, not just because they are invivo, but also because the forces and displacements that are required
to be measured are extremely small - typically a peak lateral force
of around 3gf will produce displacements of less than 1 mm. Data
is usually presented as a plot of force against displacement. In
which case an ellipse will be formed, as the component parts are
two sine waves with an identical period, but shifted in time. Such a
picture, as taken from the LSR, is shown in figure 2. The research
team is currently using the LSR to map the visco-elastic properties
of the vocal fold, using animal and human ex-vivo samples.
The LSR was jointly designed and developed by myself and Dr Paul
Stevens, and demonstrates that the team has a track record of success
in researching, designing and developing a commercial clinical
The team are now investigating new techniques that will allow similar
measurements to be made in-vivo. The most promising technique is to
employ Surface Acoustic Waves (SAW) sensors, which are capable of
detecting the very low forces in a non-contacting manner. Sensor
Technology Ltd, an UK based SME, are experts in the design of SAW
sensor devices. They have agreed to participate in a joint programme
with DMU to develop a surgical instrument that can be used to measure the visco-elastic properties of the
vocal fold in-vivo.
Collaboration With Harvard Medical School At Massachusetts Eye & Ear Infirmary (MEEI)
Dr James Kobler, Director of the Harris Peyton Mosher Laryngological Research Laboratories at Harvard
Medical School, invited me to visit and work in their laboratories last year. The Harvard group, which
includes laryngeal surgeons, voice scientists and engineers, is currently engaged in a major programme to
apply tissue engineering to repair/replace damaged vocal folds in patients who have voice disorders. A key
part of the tissue engineering process is to ensure that the implant matches the visco-elastic properties of the
natural vocal fold.
Trials of the LSR using a pig larynx and a human larynx were a success. We demonstrated that the
instrument could extract visco-elastic measurements in a repeatable manner and was sensitive enough to
measure the delicate vocal fold epithelium. The LSR also detected artificially stiffened tissue, which
suggests that it could be used to quantify and map areas where vocal fold properties have been changed by
implants or by pathology. These were the first measurements ever made of the mechanical properties of the
superficial layer of the human vocal fold in an intact larynx. A typical 2D plot of DSR (elasticity) across and
around the vocal fold, is shown below.
Saw Sensors
Surface Acoustic Waves were postulated by Rayleigh in 1885 [2], he stated that waves could be propagated
over the plane boundary between a linearly elastic half-space and a vacuum (or a sufficiently rarefied
medium such as air), where the amplitude of the waves decays exponentially with depth. The application of
the SAW phenomena for the design of non-contacting strain gauges is a recent development. Leaders in this
field are an UK company Sensor technology Ltd. Their most successful products being the application of
SAW technology to measure rotary torque [3].
It is proposed that a SAW generating device will be etched onto the probe that will be attached to the vocal
fold tissue. Acoustic waves will be generated along the surface of this probe. A co-axial tube will surround
this probe, onto which will be etched a sensing SAW element. As long as the air gap is small, theory states
that the resonant frequency of this dual SAW arrangement will alter with respect to the compression/tension
resulting from movement of the probe.
3. The Partnership
This proposal is for support for a Product Development Phase to design a ‘Mini-LSR’ for use as an in-vivo
surgical instrument to measure the Visco-Elastic properties of the vocal fold. This project represents a
collaborative venture between DMU, Harvard Medical School and 3 UK based SME companies.
Eric Goodyer of DMU will be the Project Manager and main researcher. Eric works part time for DMU and
undertakes contract design for a range of manufacturing companies. He therefore has an appreciation of
academic and industrial needs, and has extensive experience of project management. From 1982 to 1991 he
was Product Development Manager of Sira Ltd (the former Scientific Instruments Research Association).
He has undertaken a number of product development projects for SMEs funded via Business Link, and
similar product development support programmes, and has won a Smart award in his own right last year.
Other research staff at DMU will be involved in this project, including a full time Research Assistant.
Harvard Medical School’s research team, headed by Dr James Kobler will be responsible for clinical trials,
and instrument specification.
Sensor Technology is a manufacturer, and has offered cash in kind to a value of £35k; further investment is
expected as the project progresses. They will be responsible for developing the SAW sensors, and for taking
the project through to full commercial exploitation. Initial market surveys have indicated a strong interest in
this new instrument in the USA.
Paul Stevens Mechanical Design Ltd developed the precision micro-mechanics found in the full size LSR,
and will be responsible for the electro-mechanical component design. Paul developed the electro-mechanics
of the existing LSR, and works closely with Canard Design on other medical instrumentation.
Canard Design Ltd will be responsible for designing the case/packaging and associated tooling. We are
already collaborating with Canard Design on the development of two other non-related medical instruments.
4. Prospects for Exploitation
Sensor technology Ltd will be taking the product through to commercial production. Their offer of £35k
worth of in-kind support is a direct result of our initial market analysis. Considering only the US market for
this instrument in Laryngological OR environment, potential export sales of $2.4million over 5 years were
identified. This includes the base analysis unit for the instrument, plus the value of the disposable probe tips.
Other markets will need to be identified, as these potential sales figures make the overall project just about
viable, but we are confident that they will be forthcoming once we have a demonstrable product. A clear
route to commercial exploitation has been identified. We have an outline design, a manufacturer and a
This project will deliver both good science and a commercially viable product. The deliverables will be
 Identification of a range of new sensors that are suitable for in-vivo use
 New knowledge relating to the mechanical properties of the human vocal fold
 A new clinical instrument to measure the visco-elastic properties of the vocal fold
 A business plan to take the product through to full commercial production, resulting in enhanced
employment opportunities in the EU and export sales to the USA
Comparative Study Of 5 Instruments Measuring Stratum Corneum Hydration In Vitro. Fluhr J.W., Gehhng W.
Gloor M., Lazzerini S., Kleesz P, Berardesca E . Stratum Corneum 2 1998 Cardiff
Lord Rayleigh (J. Strutt). 1885. “On Waves Propagated Along The Plane Surface Of An Elastic Solid,” Proc
Lond Math Soc, (17):4-11.
Dynamic Rotary Torque Measurement Using Surface Acoustic Waves, Drives & Controls U.K. Conference
2000. Anthony Lonsdale
Mapping the Visco-Elastic Properties of the Vocal Fold. Advances in Quantitative Laryngology, Voice and
Speech Research. Hamburg April 2003. Eric Goodyer & James Kobler
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