Printed Electromechanical Sensors for Applications in Structural Health Monitoring and Surgical Simulation

The electromechanical transduction of strains and vibrations provides essential information regarding the health and status of structures and components across a wide range of industries, such as medicine, transportation, aerospace, and construction. Mechanical strain sensing can be bifurcated into a high-frequency regime (> 1 Hz) and a low-frequency regime (< 1 Hz) depending on the specific sensing application. Commercial piezoelectric sensors operating in the high-frequency regime utilize the ceramic lead zirconate titanate (PZT), but PZT is brittle and toxic. Furthermore, PZT requires high-processing temperatures to maximize piezoelectric performance. In contrast, the biocompatible and printable polymer poly(vinylidene fluoride) (PVDF) possesses a low piezoelectric coefficient (30 pC/N). A novel ferroelectric material, trimethylchloromethyl ammonium trichloromanganese (TMCM MnCl3), possesses both an excellent single-crystal piezoelectric coefficient (185 pC/N), processability from organic solvents, and six equivalent piezoelectric axes that enable observable piezoelectricity in printed polycrystalline films. In turn, this has enabled the fabrication of all-printed piezoelectric sensors using interdigitated silver electrodes for applications in structural health monitoring. Highlights from this FlexTech-funded research include the electrohydrodynamic inkjet printing of high-resolution silver interdigitated electrodes to increase the sensor signal, processing insights used to optimize the printed TMCM MnCl3 layer, and the development of a finite element model to predict the piezoelectricity of printed, polycrystalline TMCM MnCl3. In addition, this talk will discuss the development of stretchable strain sensors operating in the low-frequency regime for applications in surgical simulation. These strain sensors are comprised of a novel biocompatible and 3D-printable conductive organogel and conductive stitched electrodes. Sensors demonstrate a large strain range (300%), minimal signal drift, and low hysteresis. A lifelike skin tissue model with seamlessly integrated sensors is fabricated and utilized in a dermatological surgical simulation application to demonstrate the potential of this technology in medical education.