Multimodal MEMS vibration energy harvester with cascaded flexible and silicon beams for ultralow frequency response

Scavenged energy from ambient vibrations has become a promising energy supply for autonomous microsystems.However,restricted by device size,most MEMS vibration energy harvesters have much higher resonant frequencies than environmental vibrations,which reduces scavenged power and limits practical applicability.Herein,we propose a MEMS multimodal vibration energy harvester with specifically cascaded flexible PDMS and"zigzag"silicon beams to simultaneously lower the resonant frequency to the ultralow-frequency level and broaden the bandwidth.A two-stage architecture is designed,in which the primary subsystem consists of suspended PDMS beams characterized by a low Young's modulus,and the secondary system consists of zigzag silicon beams.We also propose a PDMS lift-off process to fabricate the suspended flexible beams and the compatible microfabrication method shows high yield and good repeatability.The fabricated MEMS energy harvester can operate at ultralow resonant frequencies of 3 and 23 Hz,with an NPD index of 1.73μW/cm^(3)/g^(2)@3 Hz.The factors underlying output power degradation in the low-frequency range and potential enhancement strategies are discussed.This work offers new insights into achieving MEMS-scale energy harvesting with ultralow frequency response.

Highly flexible,foldable,and rollable microsupercapacitors on an ultrathin polyimide substrate with high power density

The design and functionality of extremely flexible,foldable,and rollable microsupercapacitors(MSCs)with in-plane interdigital electrodes that consist of single-walled carbon nanotube(SWCNT)networks on an ultrathin polyimide substrate are demonstrated through experiments and finite element simulations.The all-solid-state MSCs can be reversibly bent,folded,and rolled purely elastically without degradation of their electrical performance.The simulation results confirm that the deformation in bent,folded,and rolled MSCs is purely elastic.The high power density(1125W cm^(–3))and small time constant(1 ms)of the present MSCs are comparable to those of aluminum electrolytic capacitors.The MSCs operate at scan rates of up to 1000 V s^(–1),are characterized by a volumetric capacitance of 18 F cm^(–3) and an energy density of 1.6 mWh cm^(–3),and exhibit superior electrochemical stability with 96% capacity retention even after 100,000 charge/discharge cycles.The developed MSCs demonstrate high potential for integration in flexible and wearable electronic systems.