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Bhatia, Divij,Kim, Wook,Lee, Sangmin,Kim, Sang Woo,Choi, Dukhyun unknown 2017 Nano energy Vol.33 No.-
<P><B>Abstract</B></P> <P>Triboelectric nanogenerators (TENG) can effectively generate electrical energy from the otherwise wasted mechanical energy in our environment. However, since vibration energy scavengers are usually driven at their resonant frequency, vibrating TENGs (VTENG) can provide maximized output power only within a few Hz of input frequencies. Here, we report tandem TENGs which are able to optimally scavenge abundant vibration energy under a wide band of input frequencies (tens of Hz and beyond). We first investigate the dynamic response of a single VTENG by parametric analyses (external forces, mass, stiffness, and gap distance) according to input frequencies. Based on coupled behavior, we complete a design protocol for a single VTENG, providing optimal power generation at a given frequency. Finally, we demonstrate a tandem system of resonant VTENGs, where maximum output power can be produced over a broad range of input frequencies between 15 and 40Hz. It is expected that our design protocol enables optimal energy conversion for an individual TENG and that tandem design will be practically useful for consistently scavenging a wide band of vibration energy from environmental sources such as vehicles, wind, and waves.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We propose tandem triboelectric nanogenerators for wide bandwidth vibration energy scavenging. </LI> <LI> We conducted systematic parametric study for vibration type triboelectric nanogenerator (VTENG) to determine the design equations. </LI> <LI> We completed a design protocol for fabricating a resonant VTENG to ensure maximum power output. </LI> <LI> Finally, we demonstrated working tandem system of optimally designed VTENGs for targeted frequency range. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Wearable elbow rehabilitation system using self-powered sensors
Divij Bhatia(바티아 디비제이),Seong Hyeon Jo(조성현),Yusung Kim(김유성),Dong Hyun Kim(김동현),Hyung-Soon Park(박형순) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.4
Increasing movement frequency and patient engagement is a crucial part of the rehabilitation process. One approach for integrating productive rehabilitation tasks with motivational features is through an interactive game. Furthermore, if moving the impaired body part can generate electricity to power the system it could motivate the patient even more. Therefore, in this work we developed a wearable elbow rehabilitation system using self-powered sensors based on the triboelectric nanogenerator. The system consisted of a 3D printed body integrated with the self-powered sensors that could provide real-time elbow joint motion data. After digitizing the acquired data, the elbow motion could manipulate objects in an interactive game made in Python language. We first provide detailed analysis of the system design and the triboelectric nanogenerator output which was enhanced using gears and material surface nano-patterning. Next we describe the sensor data processing circuit and game control using Arduino, based on the direction and extent of forearm motion. Finally we tested the wearable system and game on healthy subjects and stroke patients and analyzed the differences in subject performance which reflected their impairment level. We expect that our self-powered rehabilitation system could be used as a practical solution for home based elbow rehabilitation therapy.
Cam-based sustainable triboelectric nanogenerators with a resolution-free 3D-printed system
Lee, Younghoon,Kim, Wook,Bhatia, Divij,Hwang, Hee Jae,Lee, Sangmin,Choi, Dukhyun Elsevier 2017 Nano energy Vol.38 No.-
<P><B>Abstract</B></P> <P>Abundant rotating energies in our environment could be utilized to produce electrical power by using mechanical energy harvesters; however, rotating scavengers are limited by their low lifetimes and high costs due to the severe friction between operating materials and the necessity of precise system resolution. In this study, we report cam-based triboelectric nanogenerators (C-TENGs), where the cam transforms rotational motion into linear movement, resulting in a practically-sustainable high-performance scavenger that utilizes contact-type TENGs. Furthermore, we use bumper springs in the C-TENG system to create cost-effective and resolution-free C-TENGs, which allow the low-resolution system elements (i.e., 3D-printed components) to be easily rotated without experiencing blocking. It is demonstrated that the ratio between the spring constants of a spacer spring and a bumper spring is an important design variable to improve the output power of the C-TENG. Interestingly, we also find that the rigidity of the supporting substrate below the contacting materials is significant and enhance the output performance of TENGs over twice by adopting soft substrates. By augmenting the number of cam noses, the working frequency increases, but the output peak power is not changed due to the same contact velocity in the C-TENG. Alternatively, the output power in the C-TENG is extremely dependent on the angular velocity where the contact velocity significantly increases. We suggest that the contact velocity could be determined by analyzing the separation time in the C-TENG; this is useful because it is difficult to directly measure the velocity. Our C-TENG is demonstrated to produce a uniform high output voltage (~350V) for a long time (over 210,000 cycles) at 400rpm. The maximum output energy and average power of our C-TENG are calculated to be 6.7µJ and 3.5mW at 15MΩ, respectively. The C-TENG is practically used to power 180 commercial green light-emitting diodes (LEDs) with a bicycle. We expect that this sustainable and resolution-free 3D-printed system design will be a practical and promising solution for industrial applications of TENGs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Cam-based triboelectric nanogenerators (C-TENG) were developed for a practically-sustainable high-performance scavenger. </LI> <LI> By adopting a cam, we could utilize high rotational energies to operate contact-type C-TENGs. </LI> <LI> We employed bumper springs to create 3D printable, cost-effective and resolution-free C-TENGs. </LI> <LI> Soft substrates increased the effective contact area resulting in greater static electrification and electrical output. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>