29 Design and Optimization of 3D Printed Pressure Sensors

Faculty Mentor: Yong Lin Kong (Mechanical Engineering, University of Utah)

Total joint arthroplasty (TJA), or joint replacement surgery, is the most common solution for end-stage arthritis patients no longer responding to non-surgical treatment. From 2020 to 2021, the American Joint Replacement Registry reported 2.4 million total joint replacement surgeries for the hip and knee joints alone. However, failure rates for TJA joint implants as reported by the American Association of Hip and Knee Surgeons have been found to be 5-10% 10 years post-operatively. Common factors for failure include fracturing, implant instability, and biocompatibility concerns. However, there is currently no viable solution for implantable devices that allows for monitoring in vivo. Here we fabricated wireless pressure sensors using additive manufacturing (3D printing), and showed that printed sensors yield a measurable signal in frequency space that may be characterized for future application with implantable devices.

For this project, we designed sensors using SOLIDWORKs, simulated them to better understand their response in frequency space, and measured successful prints using a network analyzer for comparison of simulated and observed resonant frequencies. In the span of this project, five design cycles were performed to iteratively optimize the sensor design. Each design involved changes to the geometry of the previous design, adjusting inductance and capacitance to obtain a readable resonant frequency and to shift the observed frequency range. The findings from these design optimizations provide insight into adjustments necessary to shift sensor resonant frequency into a desired range and highlights the importance of Q-factor in resonant frequency readability. These findings may also be referenced for a finalized design used in compression testing and characterization. We anticipate that the integration of 3D printed pressure sensors has potential for future use in wireless internal monitoring. The use of additive manufacturing for pressure sensors offers flexibility in fabrication and design geometry, which we envision will be useful in various implantable biomedical devices such as blood pressure monitors and joint implants.