Hydroxyapatite Thick Films Research Articles

Piezoelectricity in screen-printed hydroxyapatite thick films

ABSTRACTThe discovery of piezoelectricity in calcined thin films and sintered ceramics of synthetic hydroxyapatite is of interest to understand the role of electricity in bone growth and to find use of piezoelectric implants in bone growth stimulation or deceleration and in energy harvesting to run spinal or neuro stimulators. Synthetic apatites including hydroxyapatite and a mixture of hydroxyapatite and tricalcium phosphates are extensively used in bone graft substitute and cement-less implant coating. We provide experimental evidence of piezoelectricity in screen-printed thick-films of hydroxyapatite, which may allow many real-time experiments to understand physiological significance of piezoelectricity and potential in vivo exploitation.

Detection of adsorbed cytochrome c on hydroxyapatite thick films using a microwave sensor

Abstract An interdigitated microwave sensor was used to detect the adsorption of cytochrome c on hydroxyapatite thick films. Changes in the microwave spectral response were indicative of the presence of adsorbed cytochrome c. The sensitivity of the system was also evaluated using different protein loadings on the e films. The results suggest that the microwave sensor can be utilized to detect protein.

Improved gas sensing and dielectric properties of Fe doped hydroxyapatite thick films: Effect of molar concentrations

Highlights: • We report improved gas sensing and dielectric characteristics of Fe ion exchanged HAp films. • Fe doped HAp film shows maximum gas response at relatively lower temperature. • Response and gas uptake capacity of sensors is improved for appropriate amount of Fe ions in HAp matrix. • Fe-HAp films exhibit remarkable improvement in dielectric properties compared to pure HAp. • Fe doped HAp films show significant improvement in gas sensing as well as in dielectric properties. - Abstract: In the present work Fe doped hydroxyapatite (Fe-HAp) thick films has been successfully utilized to improve the gas sensing as well as its dielectric properties. Initially, HAp nano powder is synthesized by chemical precipitation process and later on Fe ions are doped in HAp by ion exchange process. Structural and morphological modifications are observed by means of X-ray diffraction and scanning electron microscopy analysis. The sensing parameters such as operating temperature, response/recovery time and gas uptake capacity are experimentally determined. The Fe-HAp (0.05 M) film shows improved CO and CO{sub 2} gas sensing capacity at lower operating temperature compared to pure HAp. Moreover, variation of dielectric constant and dielectric loss for pure and Fe-HAp thick films are studied as amore » function of frequency in the range of 10 Hz–1 MHz. The study reveals that Fe doped HAp thick films improve the sensing and dielectric characteristics as compared to pure HAp.« less

Fe doped hydroxyapatite thick films modified via swift heavy ion irradiation for CO and CO2 gas sensing application

Abstract Swift Heavy Ion irradiation (SHI) technique is utilized to modify the structure and surface morphology of Fe doped Hydroxyapatite (Fe-HAp) thick films for CO and CO 2 gas sensing applications. Nano-crystalline HAp is synthesized by wet chemical precipitation route and ion exchange process is employed to replace of Ca ion with Fe ions. Thick film Fe-HAp sensors, having variable Fe doping concentrations, are prepared by using screen printing technique. The Fe-HAp thick films are irradiated using Ag 7+ ion (100 MeV) with variable ion fluences ranging from 3 × 10 10 to 3 × 10 13 ions/cm 2 for modifying the sensor surface. Structural and morphological changes with respect to ion fluence are observed by means of XRD, SEM and AFM analysis. The parameters such as operating temperature, response/recovery time, and uptake capacity for pristine and modified Fe-HAp sensors are experimentally determined. The investigations reveal that the SHI irradiated Fe-HAp film (3 × 10 11 ions/cm 2 ) shows improved gas sensing characteristics at relatively lower operating temperature in comparison to pristine film. It is concluded that Fe-HAp film can be a potential candidate for developing low cost, energy saver and high performance CO and CO 2 sensor.

Gas Sensing and Dielectric Studies on Cobalt Doped Hydroxyapatite thick films

This present paper deals with the investigation on effective utilization of cobalt doped hydroxyapatite (Co-HAp) thick films for improvement in gas sensing and dielectric properties. Chemical precipitation route is used for synthesis of nanocrystalline hydroxyapatite (HAp) bioceramic and ion exchange process is carried out for the partial substitution of cobalt ions in HAp matrix. Hydroxyapatite thick films, prepared using screen printing technique, are used as samples for gas sensing and dielectric measurements. The structural identification of HAp thick films is carried out using X-ray diffraction and the presence of functional groups in pure and doped HAp is confirmed by means FTIR spectroscopy. The surface morphology of these films is visualized by means of SEM and AFM analysis. Detailed study on CO2 gas sensing performance of pure and Co-HAp thick films is carried out wherein operating temperature, response/recovery times and gas uptake capacity are determined. It is remarkable to note that Co-HAp film with 0.01M cobalt concentration shows maximum sensitivity to CO2 gas at relatively lower operating temperature of 135 o C in comparison with pure HAp as well as other concentrations of cobalt doped HAp films. The frequency dependent variation of dielectric constant (K) and dielectric loss (tan δ) of HAp thick films are also studied in the range of 10 Hz-1MHz at room temperature. The result shows that increase of cobalt concentration in HAp matrix leads to increase in dielectric constant. The study reveals clear influence of cobalt substitution on dielectric properties and gas sensing properties HAp matrix. Copyright © 2013 VBRI Press.

Enhancement in CO gas sensing properties of hydroxyapatite thick films: Effect of swift heavy ion irradiation

Abstract This paper investigates the effect of swift heavy ion (SHI) irradiation on surface morphology of Hydroxyapatite (HAp) thick films and modification in gas sensing characteristics. The HAp nanopowder is synthesized by wet chemical process and the thick films are prepared by screen printing technique. These films are irradiated with Ag 7+ ions with energy of 100 MeV at different fluences ranging from 3 × 10 10 to 3 × 10 13 ions/cm 2 . X-ray diffraction and atomic force microscopy tools are employed to examine the phase and surface modification in HAp thick films due to swift heavy ion irradiation. The ion irradiation study shows that crystallinity decreases and grain size changes with increase in ion fluence. A precise study on gas sensing is carried out to confirm operating temperature of HAp thick film sensor to detect CO gas. Saturation region of the film with increasing gas concentration and other parameters such as response and recovery time are also investigated from the point of view of using HAp films as a sensor device. SHI irradiated HAp thick film shows enhancement in the gas response and saturation limit for CO gas. Furthermore, the irradiated HAp film shows fast response and recovery time for CO gas. The study concludes that nanoceramic HAp thick film is an excellent CO gas sensor at an operating temperature of 195 °C.

Surface modified hydroxyapatite thick films for CO 2 gas sensing application: Effect of swift heavy ion irradiation

Abstract Swift heavy ion irradiation (SHI) is used to modify the structural and gas sensing properties of Hydroxyapatite (HAp) thick films. The HAp thick films, prepared by screen printing technique, are irradiated with a variable fluence (3×10 10 to 3×10 13 ions/cm 2 ) of Ag 7+ ions of 100 MeV energy. XRD shows gradual change in crystallinity of the matrix with increase in ion fluence. Atomic force microscopy reveals the agglomeration of grains with pronounced cluster type structure at relatively higher ion fluence. For confirmation of efficient gas sensing of pristine and irradiated HAp thick films, repeatability and reproducibility tests are conducted in a carbon dioxide atmosphere. The parameters responsible for device applications such as, gas uptake capacity, response to test gas and recovery time of HAp film sensor are also investigated. SHI modified HAp films show the maximum enhancement in the gas response and also in increased gas uptake capacity for the fluence 3×10 11 ions/cm 2 . Moreover, SHI has resulted in modification of gas response and recovery time for CO 2 gas. The remarkable observation is to note that SHI irradiation improves the sensor characteristics of the HAp films without affecting the working temperature (165 °C) of gas sensor.