Mechanical properties of triply periodic minimal surface structures mimicking the microstructure of Woodpecker's cranial bone.

A new triply periodic minimal surface (TPMS) structure mimicking the microstructure of Great Spotted Woodpecker's cranial bone was designed, fabricated and tested in this study. It was found that the designed structures acquired better mechanical performance compared to the unit structures applied in heterogeneous porous scaffolds. The wall thickness mimicking the woodpecker's spongy bone and the TPMS surface structure were two contributors to the good mechanical performance of new designed bionic structures.

Effect of different backpack loads on physiological parame ters in walking / 生物医学工程学杂志

This study investigated the effect of prolonged walking with load carriage on body posture, muscle fatigue, heart rate and blood pressure of the tested subjects. Ten healthy volunteers performed 30 min walking trials on treadmill (speed = 1.1 m/s) with different backpack loads [0% body weight (BW), 10% BW, 15% BW and 20% BW]. The change of body posture, muscle fatigue, heart rate and blood pressure before and after walking and the recovery of muscle fatigue during the rest time (0, 5, 10 and 15 min) were collected using the Bortec AMT-8 and the NDI Optotrak Certus. Results showed that the forward trunk and head angle, muscle fatigue, heart rate and blood pressure increased with the increasing backpack loads and bearing time. With the 20% BW load, the forward angle, muscle fatigue and systolic pressure were significantly higher than with lighter weights. No significantly increased heart rate and diastolic pressure were found. Decreased muscle fatigue was found after removing the backpack in each load trial. But the recovery of the person with 20% BW load was slower than that of 0% BW, 10% BW and 15% BW. These findings indicated that the upper limit of backpack loads for college-aged students should be between 15% BW and 20% BW according to muscle fatigue and forward angle. It is suggested that backpack loads should be restricted to no more than 15% BW for walks of up to 30 min duration to avoid irreversible muscle fatigue.