Miniaturized Energy Harvesting Modules

The growing societal percentage of elderly people (eg, in Europe) will challenge the health care system in the next few decades. Recent german demographics shows that 21% of the total population are older than 65 years. This number is predicted to increase to over 30% by year of 2050. The increasing number of elderly people together with the increasing life expectancy motivates the development of implantable medical devices (IMD) for therapies such as bone and cartilage regeneration, deep brain stimulation to treat movement disorders, and fixing abnormal heart rates with pacemakers. However, a key challenge for these IMDs is their limited battery capacity. Necessary replacement is required every 5 to 10 years with an additional surgery. Moreover, chemical side effects and the large size of the batteries encourage engineers to develop either a battery with sufficient lifertime and capacity or investigate alternative energy supply mechanisms for the IMD. In this work we will main study the latter approach.

Energy harvesting technologies have attracted considerable attention in the past decade. Energy harvesters transform energy present in the environment into electrical energy. Various applications exist together with dedicated energy harvesters to address the growing demand of ubiquitous electronic systems. Medical implants, which integrate miniaturized energy harvesters, shall support the battery and thus prolong the implant's lifetime. Multiple harvesting solutions have been applied in medical implants, such as harvesting solar energy and transferring its power wirelessly to the implants. Alternatively, the kinetic energy from human motion and thermal energy from human body can be collected and provided as electrical power. 

In this proposal, the piezoelectric energy harvester, which harvests wasted mechanical vibration energy, and the themoelectric generater (TEG), which harvests human body thermal energy, are studied. To design and optimize these energy harvesters, computer-aided development processes have become state of the art because of their low cost and high efficiency. However, the capacity of today's computers is not always sufficient to meet the demands of industrial simulations. The complex geometry and multi-physics effects in energy harvesting devices have led to rather time-consuming simulations. To improve the efficiency of the simulations using existing computers, the methodology of model order reduction (MOR) was applied. The original large-scale system can be projected onto a low-dimensional subspace using MOR methods.

 

Micro-structured piezoelectric energy harvester model adapted from Wang et al. 2012 (Z. Wang, S. Matova, R. Elfrink, M. Jambunathan, C. de Nooijer, R. van Schaijk, and RJM Vullers (2012), “A piezoelectric vibration harvester based on clamped-guided beams”, Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS), pp. 1201-1204.)

 

Assembling setup of the thermoelectric generator (TEG) integrated electrically active implants positioned in the human tissue