## 1 Introduction
This approach is a potentially inexhaustible source of energy for low-power devices. Energy harvesting currently exploits four primary sources of energy--light, electromagnetic radiation, thermal gradients, and motion [8]. The significant drawbacks of energy harvesting are the difficulty in gathering energy and inconstant power generation; hence, different energy-harvesting approaches have been investigated, and piezoelectric materials have yielded favorable results in harvesting energy from mechanical vibrations [9; 10; 11; 12]. More specifically to the present study, different approaches to energy harvesting oriented toward structural-health monitoring have been studied [13]. Energy harvesting, which takes advantage of the piezoelectric effect to gather mechanical energy from the environment and to convert it into electrical energy, has been reviewed. Piezoelectric elements have been widely used to collect energy from mechanical vibrations, which make them appropriate for use in ground-vehicle chassis and civil structures, where vibrations within a frequency range impact on the piezoelectric item and generate an output voltage. The most common configuration and design used for piezoelectric-energy harvesting (PEH) employs a cantilever. A piezoelectric cantilever undergoes compression and tension cycles as it is being excited through vibration or cyclic forces; however, an important limitation of the cantilever is the limited frequency range in which these devices operate due to their resonant behavior (different beam dimensions); thus, different resonant frequencies and operating bandwidths have been studied [14]. This study presents the design and implementation of a new low-cost prototype of a smart sensor at the macroscopic scale for the measurement of mechanical strain. In addition to measurement and data-processing results, outcomes include an energy-harvesting subsystem with piezoelectric sensors in a cantilever structure and IoT-oriented cloud-computing capabilities through an online dashboard. For the transducer, the ongoing applied approach is to replace strain-gauge arrays with an MRE that contains nanoparticles. Our experimental work was neither nano nor micro, but a macro hands-on endeavor with a prototype built with commercial resources that were not considered to be highly specialized. The use of open connectivity platforms to develop the wireless communication and IoT applications is also highlighted. Moreover, this research includes exhaustive feasibility tests to convert a polymer into a smart material. In this case, different types of nanoparticles were employed to convert a strain signal (the difference between a nominal elongation and that generated when a force is applied to it) into electrical resistance. The motivation for this work was the monitoring of the chassis of ground vehicles. With information captured from the oscillations and measured strains of these structures, the next step would be to create a network of very efficient (accurate readings, energy harvesting, IoT capabilities) smart sensors to achieve better diagnoses of the state of the structures, including punctual fault location and the remaining lifetime of the structure. The rest of the article is organized as follows: Section 2 presents related reported work. Section 3 develops the design and implementation methods of each subsystem of the smart sensor, and the employed experiment material, and Section 4 describes the carried-out validation tests. Section 5 presents the preliminary results from the experiment work. Section 6 discusses the results, and Section 7 discusses our conclusions and future work.