Printed Electromechanical Sensors

Abstract

Printed electronics refers to the additive manufacture of devices with single or multiple functionalities via the deposition of inks onto flexible or deformable surfaces. This dissertation aims to utilize functional, printable materials to fabricate and characterize electromechanical sensors, which transduce a mechanical input signal to an electrical output signal. Piezoresistive-based strain sensors operating a low-frequency regime (<1 Hz) for medical simulation applications and piezoelectric-based vibration sensors operating in a high-frequency regime (> 1 Hz) for structural health monitoring applications are both described in this thesis. Monolithically integrated piezoresistive sensors can be used to quantify large deformations in lifelike tissue models. The demonstration of 3D printing of an ionogel as a stretchable, piezoresistive strain sensor embedded in an elastomer is presented as a proof-of-concept of this integrated fabrication. Subsequently, a novel class of inexpensive, conductive, non-toxic, and 3D-printable organogels was synthesized and implemented as the piezoresistive medium. Piezoelectrics transduce electromechanical inputs and outputs for a variety of applications in sensing, actuation, and energy harvesting. The high processing temperatures, brittle mechanical properties, and toxic metal composition of high-performing piezoelectrics, such as lead zirconate titanate (PZT)-based materials, limit rapid and scalable fabrication of thin, flexible electromechanical devices. A growing class of piezoelectric materials, hybrid inorganic-organic multiaxial molecular ferroelectrics, combine a promising piezoelectric performance with solution processability. All-additively manufactured piezoelectric vibration sensors with two different molecular ferroelectric compositions were fabricated and characterized for the first time. Furthermore, powders of these materials were synthesized via ball-milling, a solvent-free and scalable synthetic approach, for the first time. The electrode material, poling conditions, humidity, and piezoelectric testing conditions affected the piezoelectric response of pressed polycrystalline samples, highlighting the need for this growing field to improve transparency of experimental methods.