交变电场作用下骨表面温升的实验研究

Experimental study on temperature rise of bone surface induced by an alternating electric field

骨具有力电性质,这一性质可促进骨组织生长。骨既是生理器官又是介电材料,在交变电场作用下,其表现行为可能有生理作用。为此,本文测量了骨悬臂梁试样在交变电场下的表面温升与顶端挠度。发现在电压70V,频率为10~70kHz的交流电场下,最大表面温升达到2~4℃,最大挠度变化为9.0~78.7μm;在频率10kHz,电压为70~175V的交流电场下,最大表面温升达到4~6℃,最大挠度变化为13.0~114.3μm。同时测量了两种经典介电材料有机玻璃和聚乙烯在交变电场下的温升与顶端挠度,最大温升低于0.5℃,但是挠度与骨试样相当,所以相对高温升是骨特有的性质。将交流电压有效值替换成相同幅值的直流电压时,最大温升也低于0.5℃,基本没有挠度变化,所以相对的高温升反映了骨的交流性质。分析后认为,骨在交变电场作用下的温升由胶原的介电损耗引起。实验数据显示,骨在交变电场下,表面温度变化与加载电压的平方成正比,且在实验加载的10~70kHz频段内,骨的介电常数随频率的变化明显。

Bone has electromechanical properties,which may be available for promoting the bone tissue growing.Bone is a vital organ and also a dielectric material.Under an alternating electric field,its behaviors may play some role in biological process.This study aims to measure the temperature rise on a bone cantilever surface induced by an alternating electric field as well as the bending deflections at the free ends of the cantilevers.The experimental results show that the maximum surface temperature rise reaches 2~4℃and the maximum deflection change reaches 9.0~78.7μm under an electric field with voltage of 70 V and frequencies of 10~70 kHz.The maximum surface temperature rise reaches to 4~6℃and the maximum deflection change reaches 13.0~114.3μm under an electric field with frequency of 10 kHz and voltages of 70~175 V.Temperature rises of two typical dielectric materials polymethyl methacrylate and polyethylene,under alternative current voltage,are also measured,which are below 0.5℃.When the alternating electric voltage is changed to a direct current voltage with the same amplitude,the temperature rise is also below 0.5℃.Consequently,the relative high temperature rise represents the alternating current electric properties of bone.During the temperature rise,both the bone cantilevers and the typical dielectrics have bending deformation with similar deflections,which means that the deformations under alternating electric field represent their material properties instead of biological properties.Based on experimental results,data fitting and analysis are conducted and the results show that the high temperature rise is from the collagens in bone in dielectric loss.The analysis result also shows that the dielectric constant of bone collagen variates with the frequencies of electric field between 10~70 kHz,while the relationship of loss and the electric voltage follows the typical dielectric loss law,that is,the loss is proportional to the square of the applied voltage.