MEMS-Based Power Generation from Human Walking Motion

基于mems的人体行走运动发电本研究探索了在不给人体负重的情况下，利用人体行走运动产生大量电能的创新方法。这种发电的主要挑战是：(1)与行走运动相关的极低振动频率，(2)非周期性振动频谱，以及(3)由于低频而固有的低振动能量水平。例如，1 Hz的谐振频率需要非常低的弹簧常数和/或非常大的质量，如果悬架基于传统的质量-弹簧系统，则弹簧仅因重力而位移25厘米。除非有减小初始位移的机制，否则初始位移会使发电机的尺寸非常大。因此，利用人类的步行运动发电（负荷可以忽略不计）需要非常创新的方法。如果此次研究成功，将制造出体积小于1厘米、重量小于1克的发电机，通过人的行走（而不是跑步）产生的能量可达数十微瓦。因此，该研究将对可穿戴设备和植入式医疗设备产生重大影响，因为发电机将能够替代或补充电池。该研究还将对基于非固体弹簧、非谐振悬架、新型线圈设计和微加工等的高效电磁发电产生新的见解。该研究旨在探索各种微机电系统（MEMS）方法，在不负载或影响发电机佩戴者（总质量和体积分别为1克和1毫升）的情况下，有效地从与人类行走运动相关的振动能量中产生能量。特别研究的将是基于非固体弹簧（如磁性弹簧、抗磁性弹簧和液体弹簧）的非常规证明质量悬架系统，这些系统可以很容易地在非常低的频率上产生共振。此外，还将探索一种基于铁磁流体轴承的非谐振悬架，该悬架可以悬浮磁体阵列，并使其在很小的摩擦下移动，以便在从亚赫兹到几赫兹的广泛频率范围内发电。此外，为了提高给定体积和/或质量的输出功率水平，不仅要利用垂直面内磁通量梯度，还要利用水平面内磁通量梯度，通过利用快速变化的磁场，特别是在平行于平面的方向上，在两个相邻磁体之间的边界处（如在平面上布置南北交替方向的磁体阵列）。并将探索各种微加工技术，以制造具有非常大匝数的线圈阵列堆叠板，并以非常低的成本批量生产发电机。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

MEMS-Based Power Generation from Human's Walking Motion This research explores innovative approaches for generating substantial power from human's walking motion without loading the person. The major challenges in such a power generation are (1) extremely low vibrational frequency associated with walking motion, (2) non-periodic vibration spectrum, and (3) inherently low level of vibration energy due to the low frequency. For example, 1 Hz resonant frequency requires a very low spring constant and/or a very large mass, and the spring is displaced by 25 cm due to gravity alone, if the suspension is based on a conventional mass-spring system. The initial displacement would make the power-generator size very large, unless there is some mechanism to reduce the initial displacement. Thus, power generation (with negligible load) from human's walking motion requires very innovative approaches. The successful outcome of the research will mean a power generator smaller and lighter than 1 cc and 1 gram, respectively, that can generate up to tens of microWatts from human's walking (not running) motion. Thus, the research will greatly impact wearable devices and implantable medical devices, as the power generator will be able to replace or supplement battery. The research will also produce new insights into efficient electromagnetic power generation based on non-solid springs, non-resonant suspension, novel coil design and microfabrication, etc. The research is to explore various Microelectromechanical Systems (MEMS) approaches to efficiently generate power from vibration energy associated with human's walking motion without loading or affecting the wearer of the power generator (with a total mass and volume of 1 gram and 1 cc, respectively). Specifically studied will be non-conventional proof-mass suspension systems based on non-solid springs (such as magnetic spring, diamagnetic spring and liquid spring) that can easily be made to resonate at a very low frequency. Also explored will be a non-resonant suspension based on ferrofluid bearing that suspends a magnet array and allows it to move with very little friction, in order to generate power from a broad range of frequencies spread from sub-Hz to several Hz. Furthermore, not only the vertical magnetic-flux in-plane gradient, but also the horizontal magnetic-flux in-plane gradient, will be used in order to increase to the output power level for a given volume and/or mass (as an array of magnets with alternating north and south orientation is arranged on a planar surface) through exploiting the rapidly changing magnetic field, particularly in the direction parallel to the planar surface, at the boundaries between two abutting magnets. And various microfabrication techniques will be explored to fabricate stacked plates of coil arrays with a very large number of turns and also to mass-produce the power generator at a very low cost.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.