## 7 Conclusions and Future Work  
A low-cost macro-smart-sensor prototype manufactured with commercial technology, connected to the Internet for strain monitoring on metallic surfaces, was designed and fabricated. An alternative approach for well known and applied strain gauges was manufactured, i.e., an MR elastomer, which responded with electrical-resistance variation when force was applied to it. Moreover, the research outcomes included preliminary but relevant results on energy harvesting, and complete tests with a smart sensor that included IoT capabilities. An energy-harvesting system was explored. The research objective included the design and manufacture of a beam in cantilever-containing piezoelectric sensors fused in a special rubber. The system demonstrated that it was able to generate up to 1.6 V under the employed testing conditions; however, there was a strong opportunity area regarding voltage rectification and holding. The benefits of processing data in the cloud and presenting them graphically on the Internet were also shown. The dashboard was able to show the obtained information from the Google spreadsheet, connected to the smart sensor via a wireless protocol through the Internet, and taking only one minute to refresh the data on the dashboard. Preliminary results showed the potential of this smart sensor for health monitoring in the automotive, aeronautical, and construction industries. For these applications, smart sensors could be embedded in structures, and thus constantly monitor the state of the system and detect potential failure conditions. The prototype presented areas of opportunity for improvement. Better control to create MR elastomer samples and maintain a uniform number of nanoparticles could be tested. Moreover, the amount and array of nanoparticles could be improved to obtain a more linear and directly proportional relation between MRE strain and electrical resistance. The energy-harvesting system could also have a better design, and different cantilever geometric shapes could be tested to harvest more energy from the environment. Another area of opportunity was detected in the validation experiments, since some measurements were made with a multimeter. This condition could be improved by using embedded electrodes in the cantilever or the MRE to measure electrical resistance or generated voltage following another sensing paradigm. As future work, a potential research direction is to increase the harvested energy, and improve voltage rectification and holding efficiency. In this context, noise in the voltage measurements offers an opportunity for improvement. A possible solution would be to apply a low-pass filter or to employ electrodes for measuring electrical resistance in the MRE. The latter option was studied with dielectric elastomer sensors that had two electrodes and showed the potential to be applied in SHM and robotics, among others [50]. In addition, the signal-conditioning stage needs to be implemented. An option is to connect electrodes to the MRE and process the signal to make it suitable for the CPU. Other potential work is comparing the smart sensor with other approaches that could be developed (to the best of authors' knowledge, there is no reported product with similar attributes to the one we have reported). Additionally, after improving the characteristics and capabilities of the prototype, a digital twin could be generated to complement the monitoring and diagnoses of the system. The experiment-validation results highlighted the potential of the smart-sensor for use in diverse structural-health-monitoring applications. Conceptualization and design, J.d.-J.L.-S.; experiment development and validation-test tutoring, J.d.-J.L.-S., J.C.T.-M., and R.-A.R.-M.; state-of-the-art revision update and original-draft writing, L.C.F.-H.; paper writing--revision and editing, A.V.-M. and R.A.R.-M. All authors have read and agreed to the published version of the manuscript.