Med-Tech Innovation Smart materials
The proof of concept prototype uses a light dependent
resistor (LDR) to detect ambient light conditions. LDRs provide a simple, inexpensive solution. The LDR is a passive component: any change in resistance value defines the lateral extent of the pupil to change the lateral extent of the electrodes in response to a change in incident light intensity. The final version of the prosthesis will be self-contained and comprise of all of the required components to respond to changes in light intensity without the need for external connections. In the proof of concept prototype a hand painted image has been applied to a flat surface, this is then covered by a clear polymer cornea designed using normal K readings for the human cornea. This cover offers the necessary magnification to enhance the 3D effect of the artwork. An advantage of using an electroactive polymer film is that a more realistic pupil and iris combination is made possible, because a realistic painted iris can be provided behind the film, which is typically transparent. The variable pupil created by the changing shape of
the electrode on the polymer film creates a convincing illusion of a real varying pupil. More recent developments have focused on a “remote interface” for the device utilising the appropriate smart mobile platform, and inductive charging of the prosthetic. It is anticipated that charging the device would usually be undertaken overnight by the user. Miniaturising the current prototype presents further challenges, however, the research team plans to have the first pre-production prototype ready within two years. The benefit of the responsive prosthesis is that a realistic pupil can be created that could be easily incorporated into a custom made ocular prosthetic.
References
1. T. Cook et al., “Fourth National Audit Project. Major complications of airway management in the UK: Results of the Fourth National Audit Project of the Royal College of Anaesthetists and the Difficult Airway Society, Part 1: Anaesthesia,” Br. J. Anaesth.,106, 617–663 (2011).
2. A. Law et al., “The difficult airway with recommendations for
management, Part 1: Difficult tracheal intubation encountered in an unconscious/induced patient,” Can. J. Anesth., 60,1089– 1118 (2013).
3. J. Lapointe et al., “An ocular prosthesis which reacts to light,” Proc. SPIE 7885, Opthalmic Technologies XXI, 788512 (2011); doi:10.117/12.874078.
4. F.W. Leuschner, “Light-controlled pupil size for ocular prosthesis,” Proc. SPIE 1644, Opthalmic Technologies II, 320 (1992); doi:10.1117/12.137438.
5. H. LaFuente, US Patent 4332039 (1982). 6. F. Schliepman et al., US Patent 6139577 (2000). 7. F. Budman et al., US Patent 6576013 (2003). 8. T. Friel, US Patent 5061279 (1991).
9. P. Lotz et al., “Dielectric Elastomer Actuators using improved Thin Film Processing and nanosized Particles” Institute for Electromechanical Design, Darmstadt University of Technology, Darmstadt, Germany (2008).
Acknowledgements
The authors would like to acknowledge the invaluable contributions to the projects from Dr Andrew Norris, Nottingham University Hospital Trust; Fergal Coulter, doctoral student; and Thomas Stead, Jaz Worrell and Alexander Hughes, MSc Smart Design Students all at Nottingham Trent University, Nottingham, UK.
Professor Philip Breedon, BSc (Hons), PhD, CEng, CITP, FRSA, MBCS, MUKSB, is Professor of Smart Technologies and Course Leader MSc/MA Smart & Medical Product Design at Nottingham Trent University, Burton Street, Nottingham NG1 4BU, UK, tel. +44 (0)115 848 6424, email:
philip.breedon@
ntu.ac.uk www.ntu.ac.uk/design4health
Dr James Armstrong is Consultant Paediatric Anaesthetist at Nottingham University Hospital Trust, UK
John Pacey-Lowrie is Consultant Ocularist and Owner, Reflex Systems, Nottingham, UK
www.reflexsystems.co.uk.
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www.med-techinnovation.com September/October 2014 ¦ 15
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