**8. References**


From the wireless transmision data along with the referred metal foil strain gauge, it is suggested that the spinal fusion rods showed that roughly one third of the load were shared by the intact spine after the spine is fused. The telemetry system clearly shows the rigidity of

A telemetry system using a capacitive strain sensor has been developed for the detection of spinal fusion monitoring. The strain sensor was made using MEMS process with high sensitivity and reduced size that serves the purpose for strain detection on the spinal fusion rod. The cantilever structure of the sensor is composed of two parallel plates, galss and silicon, respectively, with a narrow gap D0 (3 μm) and a conjoint end. The bending strain sensor has the characteristics of high nominal capacitance (20 pF), high sensitivity, and compact dimensions (2 mm x 7 mm x 0.8 mm). It utilizes a variable gap configuration comprised of silicon and glass beams that are bonded at one end and open at the opposing end. This type of structure has been tested to withstand a strain range of 0 to 1000 με. The inductive link between the implant circuit and the reader was sufficient for supplying power to the implant circuit and extracting data at 10 cm distance. A specific sensor has a linear gauge factor of 252 in the capacitive domain and 249 in the frequency domain. Measurements made through air and water with a corpectomy model produced a linear response consistent with a metal foil reference gauge. The strain measurement system was also tested with the corpectomy model designed as a simplified mechanical analog of a spine section and was then tested using a human spine. For the biomechanics application, the sensor is expected to be in a fluidic environment. The tests of the corpectomy model placed in water tank were successful in showing that measurements were possible in conditions present in-vivo. The read range was limited to 10 cm due to the reader design used and the sensor coil design constraints. Finally, a test performed using a human spine showed the wireless implant detected strain roughly one third of the load were shared by

The authors would like to express the appreciation to Tommy Roussel, Tom Carroll, Don Yeager, John C. Jones, Dr. Michael Voor, Dr. Rolando Puno and Robert L Burden for their

Aebersold, J.W.; Hnat, W.P.; Voor, M.J.; Puno, R.M.; Jackson, D.J.; Lin, J.T.; Walsh, K.M.&

Arshak, K.I.; Collins, D. & Ansari, F. (1994). New high gauge-factor thick-film transducer based on a capacitor configuration, Int. J. Electronics, 1994 vol. 77 No. 3, 387-399.

spinal fusion detection system, J. Med. Devices 1 (June 2007) 159-164. Akar, O. ; Akin, T.& Najafi, K. (2001) A wire less batch sealed absolute capacitive pressure

J.F. Naber (2007). Development of a strain transferring sensor housing for a lumber

assistance with the modeling, test setups and surgery performance.

sensor, Sensor and Actuator A 95 (2001) 29-38.

the intact spine.

**6. Conclusion** 

the intact spine after the spine is fused.

**7. Acknowledgment** 

**8. References** 


**4** 

**Ubiquitous Piezoelectric Sensor** 

**Network (UPSN)-Based Concrete** 

Seunghee Park and Dong-Jin Kim

*EngineeringSungkyunkwan University Cheoncheon-dong Jangan-gu Suwon* 

*Republic of Korea* 

**Curing Monitoring for u-Construction** 

*Department of Civil and Environmental Engineering/u-City Design and* 

Recently, there has been increasing demand for high-rise buildings or wide-span bridges. These structures are constructed with a mount of mass concrete. However, the concrete might be susceptible to brittle fracture if the curing process is inadequate. Therefore, to prevent this drawback, it is essential to predict the strength development of concrete during the curing process. In addition, real-time monitoring of the curing strength is important for reducing the construction time and cost because it can determine the appropriate curing time to achieve sufficient strength to progress to the next phase safely. The in-situ strength of concrete structures can be determined with a high precision by performing the strength testing and/or material analysis on core samples removed from the structure (Irie et al., 2008). However, this method might destroy the concrete structure. Therefore, a range of methods based on the thermal, acoustical, electrical, magnetic, optical, radiographic, and mechanical properties of the test materials have been developed to monitor the strength development without damaging the host structures (ACI Committee 228, 2003; Lamind and Pielert, 2006; Metha and Monterio, 2005). These methods typically measure certain properties of concrete from which the strength and/or elastic constants can be estimated. Among these techniques, several methods using a Schmidt hammer or an integrated temperature have been normally used. However, these are unsuitable for use at construction sites because they do not allow real-time monitoring of the curing process of concrete

The recent advent of smart materials, particularly piezoelectric materials, can provide a solution for the real-time monitoring for strength development. Electromechanical impedance techniques that employ piezoelectric materials have emerged as a potential tool for the implementation of a built-in monitoring system for civil infrastructures (Park G. et al., 2000, 2003; Park S. et al. 2005, 2006, 2011). This technique utilizes high-frequency structural excitation, which is typically > 20 kHz from surface-bonded PZT (Lead-Zirconate-Titanate) patches, to sensitively monitor the changes in the mechanical impedance of the test structures. Furthermore, the recent advances in online monitoring, including actuation and sensing, on-board computing, and radio-frequency (RF) telemetry, have improved the

**1. Introduction** 

structures at inaccessible places.

Suster, M.; Chaimanonart,; N.; Guo,J.; Ko, W. H. & Young, D. J. (January 2005). Remote-Powered high-performance strain sensing microsystem, Technical Digest, the 18th IEEE International Conference on Micro Electro Mechanical Systems, Miami, Florida, January 2005, pp.255-258.
