Journal of the European Ceramic Society 27 (2007) 4191–4194 Biomedical instrumentation based on piezoelectric ceramics J.L. Pons * , E. Rocon, A. Forner-Cordero, J. Moreno Grupo de Bioingenier´ ıa, Instituto de Autom´ atica Industrial, CSIC Ctra. Campo Real, km. 0,200, 28500 Arganda del Rey, Madrid, Spain Available online 30 March 2007 Abstract New sensors and actuators based on emerging transducer technologies can play a crucial role in the field of biomedical instrumentation and rehabilitation technologies. Piezoelectricity and transducers based on the piezoelectric effect might lead to the adoption of compact sensor and actuator solutions in this field. This paper addresses a review of piezoelectric and piezoresistive transducer applications in the field of biomedical instrumentation. As an emerging application field, the potential implementation of these transducers in inertial motion analysis is addressed. The potential applications for these devices are high but we will focus on piezoelectric sensors in the area of inertial and portable biomechanical measurement systems and on piezoelectric actuators in active orthotics. © 2007 Elsevier Ltd. All rights reserved. Keywords: Sensors; Actuators; Biomedical applications; Piezoelectric properties; Transducers 1. Introduction Piezoelectric and piezoresistive materials allow the construc- tion of new sensors and actuators which have a number of applications in the fields of biomechanics, clinical medicine, sports, technical aids to compensate for physical disabilities, sport devices, ergonomics and the evaluation of biomechanical loads at the workplace and, finally, future leisure applications of these devices can be foreseen as their cost is reduced and their use widespread. It can be considered that the use of piezoelectric and piezore- sistive accelerometers started in the eighties with the low weight low cost uniaxial accelerometers. They were applied to mea- sure vibration (ergonomics), impacts (such as the heel-strike) and also other activities. However, the use of inertial sensors in biomechanical measuring application, remained marginal until the apparition of new devices such as the low mass piezoelectric gyroscopes that allow the encapsulation in a small size box of an ensemble of 3D gyroscopes and accelerometers. The use of pressure sensors to record the contact forces between different parts of the body and the support surfaces started also in the eighties. Two applications were focused on the measurement of the pressures under the plantar aspect of the * Corresponding author. E-mail address: jlpons@iai.csic.es (J.L. Pons). foot and under the supporting areas of disabled people that must sit down or lie during prolonged periods of time. The interaction of the human with the environment in terms of forces can also be monitored by means of piezoelectric solutions. In this regard, the three-dimensional interaction force at the foot during walk- ing is a typical example of an application field that has been consolidated with, for example, piezoelectric ground reaction force plates. A major limitation of current measuring devices in biome- chanics is that they often restrict the experiments to a limited measurement field within the laboratory walls, thus limiting the natural execution of movements such as walking or running. 1 However, it is very useful to measure the movement under real environments and with longer time spans. An example of this fact is the analysis of the variability of gait, which could be a powerful indicator of gait stability problems and its use is grow- ing rapidly in the last year. 2 A new measuring technology which enables ambulatory measurements will allow a significant scien- tific breakthrough in the field of biomedicine or robot for human interaction. Inertial sensors based on piezoelectric accelerome- ters and gyroscopes might be this technology as they would enable ambulatory biomechanical measurements. All the above presented examples are sensor instances of piezoelectric transducer potential applications. Advanced actu- ators might also benefit from the driving characteristics of the converse piezoelectric effect. The field of rehabilitation tech- nologies is plenty of potential applications in which the advent 0955-2219/$ – see front matter © 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.jeurceramsoc.2007.02.126