One century ago, ferroelectricity and then piezoelectricity were discovered using Rochelle salt crystals. Today, modern societies are invited to switch towards a resilient and circular economy model. In this context, this work proposes a method to manufacture piezoelectric devices made from agro-resources such as tartric acid and polylactide significantly reducing the energy budget without requiring any sophisticated equipement. These piezoelectric devices are manufactured by liquid phase epitaxy grown Rochelle salt (RS) crystals into a 3D printed poly(Lactic acid) (PLA) matrix being the artificial squared meshes which mimic the natural wood anatomy. This composite material can easily be produced in any fablab with renewable materials and at low processsing temperatures, reducing then the total energy consumed. Manufactured biodegradable samples are fully recyclable and have good piezoelectric properties without any pooling step. The measured piezoelectric coefficients of manufactured samples are higher than many piezoelectric polymers such as PVDF-TrFE.

This paper introduces a low-tech capacitive micromachined ultrasonic transducer (CMUT) designed with low environmental footprint materials. The fabrication process involves a copper plate as the fixed bottom electrode, a polymer-based adhesive as a dielectric material, and an aluminum foil as the top electrode.Finite element simulations include studies of displacement, mechanical stresses, and eigenfrequency. Experimental measurements validate the device's electromechanical behavior, showing an eigenfrequency of 88.6 kHz and a displacement of 22 pm. The low-tech CMUT demonstrates potential for applications such as ultrasonic actuation and energy harvesting, offering simplicity, biocompatibility, and low environmental impact. While not directly ready for applications, these transducers provide hands-on experience with technology similar to high-performance silicon-based implementations. These low-tech MUTs are perfect practical case studies for teaching purposes, combining simulation and experimental validation.