This investigation and morphology analysis of porous structure of some kinds of natural materials such as chicken eggshell, partridge eggshell, pig bone, and seeds of mung bean, soja, ginkgo, lotus seed, as well as the epidermis of apples, with SEM (Scanning Electronic Microscope) showed that natural structures’ pores can be classified into uniform pores, gradient pores and multi pores from the viewpoint of the distribution variation of pore density, size and geometry. Furthermore, an optimal design of porous bearings was for the first time developed based on the gradient configuration of natural materials. The bionic design of porous structures is predicted to be widely developed and applied in the fields of materials and mechanical engineering in the future.

We propose a new high performance magnetometer using a single magneto-impedance (MI) sensor with a peak to peak voltage detector by synchronized switching (shortened: Pk-pk VD-type MI magnetometer), which is aimed to measure a extremely weak magnetic field ranging from nT (10-9 T) to pT (10-12 T), based upon the conventional MI magnetometer which is used in the electronic compass. In order to enhance sensitivity and reduce noise, the Pk-pk VD-type MI magnetometer detects both the positive peak and negative peak in induced voltage waveform of pick-up coil. In this paper, for demonstrating the performances of Pk-pk VD-type MI magnetometer, we investigate the magnetic field sensitivity and the magnetic noise spectral density. We demonstrated that the noise level of Pk-pk VD-type MI magnetometer is lower than 2 pT/Hz1/2 for the frequency range from 1 Hz to 100 Hz which is much better than the conventional MI magnetometer. We discuss the noise performance of the Pk-pk VD-type MI magnetometer. According to the results obtained in this paper, we expect this proposed MI magnetometer can be widely used for extremely weak magnetic field detection.

In order to achieve the alpha rhythm and visual event-related fields (ERFs) measurements at room temperature, we have newly proposed a high-performance magneto-impedance (MI) sensor system with peak-to-peak voltage detector by synchronized switching, which utilizes the time-differential measurement in each MI element for suppressing the low-frequency noise components and increasing the stability of the sensor system. A high field detection sensitivity with good linearity is obtained via new MI sensor system, which is approximately 1.3x higher than that of the previous MI gradiometer. The noise level we achieved here is lower than 2 pT/Hz^1/2 in an unshielded environment, for the frequency range of 1-100 Hz. Meanwhile, we have demonstrated the new MI sensor system for room temperature alpha rhythm and visual ERFs measurements. We have achieved a clear sensitivity for spontaneous brain activity with SNR of about 8. As expected, the alpha rhythm signals simultaneously measured by EEG and MI sensor are significantly attenuated when the subject opens eyes and intensified with closed eyes. The considerable enhancement of alpha rhythm measured by MI sensor when the subject had closed eyes further evidences the signals recorded are emanating from spontaneous brain activity. For visual ERFs measurements, we have achieved a clear sensitivity for P300 brain activity for all subjects and demonstrated the tendency of P300 latency to increase with the target/standard discrimination difficulty.

We have developed a high-performance magnetoimpedance (MI) gradiometer with a peak-to-peak voltage detector by synchronized switching (shortened: pk–pk VD-type MI gradiometer) for biomagnetic signal measurement in an unshielded environment at room temperature. This newly developed MI gradiometer detects both the positive peak and the negative peak of the induced voltage waveforms in pick-up coils for enhancing sensitivity and reducing noise level. In this paper, we have investigated the sensitivity and noise level of this new MI gradiometer. The noise level we achieved here is lower than 2 pT/Hz ^1/2 in an unshielded environment for the frequency range of 1–100 Hz. Meanwhile, we have also demonstrated the pk–pk VD-type MI gradiometer for magnetocardiography (MCG) measurements in an unshielded environment and at room temperature with simultaneous measurements of electrocardiography. We have achieved the real-time measurements of R peak in MCG wave using pk–pk VD-type MI gradiometer with an amplitude of 100 pT, when the distance between the MI sensor and the chest surface is 10 mm, in sitting position. Moreover, a clear R wave and T wave of MCG are observed via pk–pk VD-type MI gradiometer, in averaging over six and eight cycles. The room temperature measurements of R wave and T wave in MCG waveform by averaging processing over 10 s (10–15 cycles) without any shielding equipment will contribute to the diagnosis of heart disease.

In order to further improving noise performance and achieving higher spatial resolution for bio-magnetic sensing, there is a tendency to develop a multi-channel integrated system for micro magnetic sensors. In this study, we have developed a high resolution programmable oversampling MI sensor system, as a unit module for multi-channel integrated bio-sensor system, based on Pk-pk VD-type MI magnetometer. We have achieved a high field detection sensitivity with good linearity, and a noise level lower than 1 pT/Hz^1/2, by utilizing the time-differential measurement in each MI element for suppressing the low frequency noise components and increasing the stability of sensor system. Meanwhile, the proposed MI sensor system can be easily enlarged into multi-channel system, and is more suitable for integration and mass production. Furthermore, we have successfully achieved the real time R peak and T wave measurements of magnetocardiography (MCG) via new MI sensor system, with a high real time signal-to-noise ratio (SNR) of about 20 dB. We have at the first time achieved the clear P wave measurements of MCG using MI sensor, in an unshielded environment. The real time MCG measurements via new MI sensor system at room temperature, in an unshielded environment, will contribute to the diagnosis of heart disease.