Condition monitoring of bones using piezo-transducers
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Condition monitoring of bones using piezo-transducers S. Bhalla · R. Suresh
Received: 5 June 2011 / Accepted: 5 April 2013 © Springer Science+Business Media Dordrecht 2013
Abstract This paper explores the feasibility of employing piezoelectric ceramic (PZT) patches as biomedical sensors for monitoring condition of bones, through experimental studies on human and rabbit bones. Conductance signatures of PZT patches bonded to bones are acquired using the electro-mechanical impedance (EMI) technique, while the bones are subjected to varying conditions such as and density changes, occurrence of cracks and fracturing. The changes in the signature correlate fairly well with the changes in the condition of the bones. Finally, the effect of healing process is experimentally simulated on rabbit bones, which showed that the conductance signature of the bones shifted back towards the original state after rejoining. The overall results of the study demonstrate good prospects of using PZT patches as bio-medical sensors. Keywords Bone · Electro-mechanical impedance (EMI) technique · Fracture · Piezoelectric ceramic (PZT) patch
S. Bhalla () Department of Civil Engineering, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India e-mail: [email protected] R. Suresh Centre for Biomedical Engineering, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India
1 Introduction Bones constitute the main load bearing structure of the body. Their mechanical properties undergo changes after an injury, while healing and during diseased conditions, such as osteoporosis, which shows incidence among the elderly population. This paper explores the possibility of employing miniaturized piezoelectric ceramic (PZT) patches as bio-medical sensors to monitor the condition of bones by detecting changes occurring in their mechanical properties. The studies involving piezo-transducers so far have primarily focused on their use as damage diagnosing sensors [1–7], and that too mainly for structural systems. This paper, on the contrary, explores their application as bio-medical sensors to monitor not only damage but also the reverse phenomenon, that of healing, in the case of bones, a bio-mechanical structural system. The proposed technique, which involves structural dynamic measurements, is significantly different from the conventional techniques for biological systems. During the recent years, there has been a growing interest in the bio-medical community to utilize the direct and the converse effects of the PZT patches for clinical applications. Bender et al. [8] reported the use of embedded PZT patches to monitor capsule formation around soft tissue implants in Sprague-Dawley rats via the electro-mechanical impedance (EMI) technique. Interestingly, their observations were similar to those of Soh and Bhalla [9], who demonstrated the EMI technique for monitoring strength, damage
Meccanica
Fig. 1 Experiment by Bhalla and Bajaj (2008). (a) Chicken femur instrumented with PZT actuator-sensor pair. (b) FRF in form
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