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. 2021 Jan;32(1):16-28.
doi: 10.1177/1045389X20948581. Epub 2020 Aug 20.

Parametric Study of a Triboelectric Transducer in Total Knee Replacement Application

Alwathiqbellah Ibrahim  1 , Geofrey Yamomo  2 , Ryan Willing  2 , Shahrzad Towfighian  3
Affiliations

Parametric Study of a Triboelectric Transducer in Total Knee Replacement Application

Alwathiqbellah Ibrahim et al. J Intell Mater Syst Struct. 2021 Jan.

Abstract

Triboelectric energy harvesting is a relatively new technology showing promise for biomedical applications. This study investigates a triboelectric energy transducer for potential applications in total knee replacement (TKR) both as an energy harvester and a sensor. The sensor can be used to monitor loads at the knee joint. The proposed transducer generates an electrical signal that is directly related to the periodic mechanical load from walking. The proportionality between the generated electrical signal and the load transferred to the knee enables triboelectric transducers to be used as self-powered active load sensors. We analyzed the performance of a triboelectric transducer when subjected to simulated gait loading on a joint motion simulator. Two different designs were evaluated, one made of Titanium on Aluminum, (Ti-PDMS-Al), and the other made of Titanium on Titanium, (Ti-PDMS-Ti). The Ti-PDMS-Ti design generates more power than Ti-PDMS-Al and was used to optimize the structural parameters. Our analysis found these optimal parameters for the Ti-PDMS-Ti design: external resistance of 304 MΩ, a gap of 550 μm, and a thickness of the triboelectric layer of 50 μm. Those parameters were optimized by varying resistance, gap, and the thickness while measuring the power outputs. Using the optimized parameters, the transducer was tested under different axial loads to check the viability of the harvester to act as a self-powered load sensor to estimate the knee loads. The forces transmitted across the knee joint during activities of daily living can be directly measured and used for self-powering, which can lead to improving the total knee implant functions.

Keywords: Energy Harvesting; Gait loading; TKR; Triboelectric harvester.

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Figures

Figure 1.
Figure 1.
(a) Schematic of the triboelctric energy harvester. (b) 3D model of the instrumented knee implants simulator
Figure 2.
Figure 2.
The experimental setup used to test the triboelectric harvesters using AMTI VIVO simulator.
Figure 3.
Figure 3.
Microscopic images for the triboelectric harvesters (a) Ti-PDMS-Al. (b) Ti-PDMS-Ti. The upper Ti layer looks different because in (a) the Ti layer is 3D printed, while in (b) it is CNC machined.
Figure 4.
Figure 4.
(a) Load profile for a knee partial gait load simulated by AMTI VIVO joint motion simulator. (b) Generated output voltage signal.
Figure 5.
Figure 5.
Zoomed-in and overlapped signals of the gait profile and the corresponding output voltage.
Figure 6.
Figure 6.
(a) Long-term voltage outputs of Ti-PDMS-Al at a different number of cycles. Test performed at Quarter gait load and 3 Hz frequency, where M indicates (medial) and L indicates (lateral) portions. The standard deviations and standard error in the Lateral and Medial positions are (0.16, 0.28) and (0.16, 0.09), respectively. (b) Average RMS voltage outputs of Ti-PDMS-Al at the lateral and medial locations for quarter gait load. The standard deviations and standard error in the Lateral and Medial positions are (0.64, 0.72) and (0.46, 0.51), respectively.
Figure 7.
Figure 7.
RMS voltage and average power outputs of Ti-PDMS-Al at the medial location for different gait loads.
Figure 8.
Figure 8.
(a) Average power outputs of Ti-PDMS-Al and Ti-PDMS-Ti triboelectric harvesters at medial location under quarter gait load and 1 Hz frequency. (b) Average power outputs of Ti-PDMS-Ti at the medial location as the gait frequency varies.
Figure 9.
Figure 9.
(a) Schematic of the triboelectric energy harvester configuration, (b) Actual triboelectric energy harvester prototype.
Figure 10.
Figure 10.
(a) Load profile for a half-sine-wave load simulated by MTS machine. (b) Generated output voltage.
Figure 11.
Figure 11.
Zoomed-in and overlapped signals of the half-sine force simulated by MTS machine and the corresponding output voltage.
Figure 12.
Figure 12.
(a) The variation of the average power with external resistance. Optimal resistance found to be 304 MΩ. (b) The variation of the average power with the gap separation distance. Optimal initial gap found to be 550 μm. (c) The variation of the average power with PDMS thickness. Optimal PDMS thickness found to be 50μm.
Figure 13.
Figure 13.
(a) The variation of the average voltage with applied axial load. (b) The variation of the average power with applied axial load.
See this image and copyright information in PMC

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