One of the main causes of food spoilage is the lipid oxidation of its components, which generates the loss of nutrients and color, together with the invasion of pathogenic microorganisms. In order to minimize these effects, active packaging has played an important role in preservation in recent years. Therefore, in the present study, an active packaging film was developed using polylactic acid (PLA) and silicon dioxide (SiO₂) nanoparticles (NPs) (0.1% w/w) chemically modified with cinnamon essential oil (CEO). For the modification of the NPs, two methods (M1 and M2) were tested, and their effects on the chemical, mechanical, and physical properties of the polymer matrix were evaluated. The results showed that CEO conferred to SiO₂ NPs had a high percentage of 2,2-diphenyl-l-picrylhydrazyl (DPPH) free radical inhibition (>70%), cell viability (>80%), and strong inhibition to E. coli, at 45 and 11 µg/mL for M1 and M2, respectively, and thermal stability. Films were prepared with these NPs, and characterizations and evaluations on apple storage were performed for 21 days. The results show that the films with pristine SiO₂ improved tensile strength (28.06 MPa), as well as Young’s modulus (0.368 MPa) since PLA films only presented values of 27.06 MPa and 0.324 MPa, respectively; however, films with modified NPs decreased tensile strength values (26.22 and 25.13 MPa), but increased elongation at break (from 5.05% to 10.32–8.32%). The water solubility decreased from 15% to 6–8% for the films with NPs, as well as the contact angle, from 90.21° to 73° for the M2 film. The water vapor permeability increased for the M2 film, presenting a value of 9.50 × 10⁻⁸ g Pa⁻¹ h⁻¹ m⁻². FTIR analysis indicated that the addition of NPs with and without CEO did not modify the molecular structure of pure PLA; however, DSC analysis indicated that the crystallinity of the films was improved. The packaging prepared with M1 (without Tween 80) showed good results at the end of storage: lower values in color difference (5.59), organic acid degradation (0.042), weight loss (24.24%), and pH (4.02), making CEO-SiO₂ a good component to produce active packaging.

The internet of medical things (IoMT) is used for the acquisition, processing, transmission, and storage of medical data of patients. The medical information of each patient can be monitored by hospitals, family members, or medical centers, providing real-time data on the health condition of patients. However, the IoMT requires monitoring healthcare devices with features such as being lightweight, having a long lifetime, wearability, flexibility, safe behavior, and a stable electrical performance. For the continuous monitoring of the medical signals of patients, these devices need energy sources with a long lifetime and stable response. For this challenge, conventional batteries have disadvantages due to their limited-service time, considerable weight, and toxic materials. A replacement alternative to conventional batteries can be achieved for piezoelectric and triboelectric nanogenerators. These nanogenerators can convert green energy from various environmental sources (e.g., biomechanical energy, wind, and mechanical vibrations) into electrical energy. Generally, these nanogenerators have simple transduction mechanisms, uncomplicated manufacturing processes, are lightweight, have a long lifetime, and provide high output electrical performance. Thus, the piezoelectric and triboelectric nanogenerators could power future medical devices that monitor and process vital signs of patients. Herein, we review the working principle, materials, fabrication processes, and signal processing components of piezoelectric and triboelectric nanogenerators with potential medical applications. In addition, we discuss the main components and output electrical performance of various nanogenerators applied to the medical sector. Finally, the challenges and perspectives of the design, materials and fabrication process, signal processing, and reliability of nanogenerators are included.