## 3 Results  
The pressure waveforms' output by the air pressure controller were approximately square with the rising and falling time not exceeding 1 s. Considering the limitation of the data acquisition time, the selected duration of the pressure was about 65 s and three amplitudes of 100 kPa, 150 kPa and 200 kPa were selected in the test. Four specimens were measured in the test, each specimen is repetitively measured five times under each of the three pressures. To examine whether the ambient electromagnetic field disturbs the measured data, we first measured the streaming potentials within 100 s when there was no pressure. The measured data were almost zero and the curve was nearly horizontal, as shown in Figure 2A, which was taken as the reference point of the measurement system. Figure 1: **(A)** Specim and its location in the diaphysis of bovine tibias. **(B)** Schematic diagram of measurement system. Figure 2: _Cont._  
The variations of streaming potential with time were obtained under the three pressures. The curves of the streaming potential versus time of the four specimens are similar in shape. Each specimen corresponds to 15 curves. Trying to plot the fifteen curves in one figure, is rather complicated. To make the figures clear, also to provide relatively detailed results, differently numbered of curves are displayed in each figure. In Figure 2B, the three curves of streaming potentials are the results of specimen one under the three pressers respectively, and any two curves with the same color are corresponding to each other. Each of the five curves in Figure 2C,D are the results of specimen two and 3 under the 100 kPa and 150 kPa, respectively. In Figure 2E the fifteen curves are the results of specimen four under the 100 kPa, 150 kPa and 200 kPa respectively. The five black curves represent the streaming potentials under the 100 kPa; the five red curves correspond to the 150 kPa and the five blue curves to the 200 kPaThe characteristics of the streaming potentials measured are that any curve of streaming potential has a negative and positive pulse corresponding to the rising and falling edges of the pressure profile respectively, and the amplitudes of the negative and positive pulse are approximately equal and proportional to the pressures applied, as shown in Figure 3A-C. Taking specimen one as an example, in Figure 3A, the three amplitudes of the measured streaming potential pulses are \(-0.472\) mV, \(-0.806\) mV and \(-1.118\) mV corresponding to the three rising edges of pressures of 100 kPa, 150 kPa and 200 kPa respectively, and those corresponding to the three falling edges are 0.555 mV, 0.941 mV and 1.156 mV respectively (Figure 3B). Figure 2: (**A**) Curves of streaming potential of specimen one without pressure. (**B**) Curves of streaming potential versus time for specimen one under the three pressures selected. (**C**) Curves of streaming potential versus time for specimen two under 100 kPa. (**D**) Curves of streaming potential versus time for specimen three under 150 kPa. (**E**) Total fifteen curves of streaming potential versus time for specimen four under 100, 150 and 200 kPa. According to Equation (1), the streaming potential is proportional to the pressure increment applied to the capillary or thin tube. However, as shown in Figure 2, during the pressure holding period (65 s), the streaming potentials measured increased continuously instead of being constant, and  
Figure 3: **(A) Negative pulse amplitudes corresponding to the loading edges. (B) Pulse amplitudes corresponding to the unloading edges. (C) Slopes under the pressure holding stage. **  
the maximally increased amplitude can reach 8 mV, far greater than the maximum pulse amplitude of 1.8 mV. The variations of the potentials with time during the pressure holding process are fitted linearly. However, in the first ten seconds the curves or potentials do not increase monotonically with time, they may or may not increase or even decrease as shown in Figure 2B-E. After that the curves increase approximately linearly.