In the recent years, several biomedical applications of lead zirconate titanate piezo-electric ceramic patches based on the electro-mechanical impedance technique have been reported in the literature. However, practical application of the technique on live subjects is severely hampered due to the requirement of bonding the patch with bone or cartilage with an adhesive. In addition, live subjects have skin cover over the bone. This article proposes and evaluates the feasibility of employing lead zirconate titanate patches as biomedical sensors in non-bonded configuration for assessing the physiological conditions of bones. For this purpose, a special design is proposed where the lead zirconate titanate patch is first bonded on a thin aluminum strip, which is in turn clamped securely on the biomedical subject. The proposed configuration is investigated both in vitro and in vivo. The non-bonded piezo sensors are first investigated to identify dynamic parameters of the bone through lab-based experimental study involving artificial bones. Thereafter, physiological damage and decay conditions are artificially simulated in the experimental bones and the same are correlated with changes in conductance signatures from the non-bonded piezo sensor as well as the lead zirconate titanate patch in the conventional adhesively bonded (direct bonding to the subject) configuration. The trend of the conductance signatures in the healthy and the damaged conditions from the non-bonded piezo sensor is found to correlate well with the corresponding signatures from the directly bonded piezo sensor. At the same time, the repeatability of the signatures is also found to be satisfactory. After success in bare bones, the non-bonded piezo sensor configuration is extended to monitor the condition of bones covered with skin and tissue, simulated in the lab with the aid of silicone-based coating. Finally, a proof-of-concept experiment on a live human subject is successfully demonstrated. The overall results of the study demonstrate very good prospects of employing lead zirconate titanate patches in non-bonded piezo sensor mode for monitoring the condition of human bones and other related biomedical subjects.
Directly bonded piezo sensor, conventionally employed in the electromechanical impedance (EMI) technique, although a proven candidate for structural health monitoring, is severely constrained in its application in the biomedical field due to its bonding requirement. In contrast, nonbonded piezo sensor (NBPS) provides a viable platform to assess the condition of human bones, tissues, and other biomedical subjects using the EMI technique without inflicting pain or irritation to the skin. The name NBPS was coined to emphasize that there was no direct bonding between the PZT patch and the live subject; instead, the PZT patch was bonded to a supporting medium, which maintains the mechanical interaction between the PZT patch and the subject.However, there are several aspects in the analysis of NBPS configuration that cannot be addressed completely through experimental study due to measurement constraints, cost, and time. For example, experimentally changing the density of bone continuously to study the osteoporosis effect is a tedious task warranting large number of specimens. This paper presents a detailed parametric study based on finite element method covering condition monitoring of human bones using the NBPS configuration. It is for the first time that 3D analysis for specimen identification and damage detection in bones using NBPS has been carried out. In addition to the validation of the numerical model against the previously established experimental studies involving bones, quantification of the extent of damage and its localization has been investigated. The density changes due to osteoporosis in bones are comprehensively investigated by the NBPS including the quantification aspect of osteoporosis/damage. Definite acquisition of bone signature and detection of physiological changes in bones are achieved even with the presence of skin, muscle, and fat layers on the bone.
Good health of bones is of the utmost importance to human beings. Smart materials like lead zirconate titanate (PZT) patches are small in size and carry less weight, which makes them most apt for biomedical structural health monitoring (BSHM). In the past, focus on the development of low-cost non-invasive techniques for real-time monitoring of critical bones has been undertaken as an alternative to current diagnosis techniques such as dual x-ray absorptiometry (DEXA), which is not portable and emits radiations. This paper presents a study to evaluate a previously developed non-bonded piezo sensor (NBPS)-based diagnostic technique for non-invasive detection of osteoporosis, in the framework of the electro-mechanical impedance (EMI) technique. As part of the study, the experimental trials in the paper are performed for comparing DEXA and bone electro-mechano gram (BEMG) on healthy subjects as well as those with osteoporosis. It was found that BEMG identified structural system for healthy and osteoporotic subjects were quite different leading to a new technique to identify osteoporosis.
This paper presents a case for extension of structural health monitoring (SHM) technologies to offer solutions for biomedical problems. SHM research has made remarkable progress during the last two/ three decades. These technologies are now being extended for possible applications in the bio-medical field. Especially, smart materials, such as piezo-electric ceramic (PZT) patches and fibre-Bragg grating (FBG) sensors, offer a new set of possibilities to the bio-medical community to augment their conventional set of sensors, tools and equipment. The paper presents some of the recent extensions of SHM, such as condition monitoring of bones, monitoring of dental implant post surgery and foot pressure measurement. Latest developments, such as non-bonded configuration of PZT patches for monitoring bones and possible applications in osteoporosis detection, are also discussed. In essence, there is a whole new gamut of new possibilities for SHM technologies making their foray into the bio-medical sector.
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