Three-Dimensional MOF-Assisted Self-Polarized Ferroelectret: An Effective Autopowered Remote Healthcare Monitoring Approach

In recent years, flexible and sensitive pressure sensors are of extensive interest in healthcare monitoring, artificial intelligence, and national security. In this context, we report the synthetic procedure of a three-dimensional (3D) metal-organic framework (MOF) comprising cadmium (Cd) metals as nodes and isoniazid (INH) moieties as organic linkers (CdI₂-INH═CMe₂) for designing self-polarized ferroelectret-based highly mechano-sensitive skin sensors. The as-synthesized MOF preferentially nucleates the stable piezoelectric β-phase in poly(vinylidene fluoride) (PVDF) and also gives rise to a porous ferroelectret composite film. Benefiting from the porous structure of 3D MOFs, composite ferroelectret film-based ultrasensitive pressure sensor (mechano-sensitivity of 8.52 V/kPa within 1 kPa pressure range) as well as high-throughput ( power density of 32 μW/cm²) mechanical energy harvester (MEH) has been designed. Simulation-based finite element method (FEM) analysis indicates that the geometrical stress confinement effect within the interpore region of the ferroelectret structure synergistically influences the mechano-electrical property of the MEH. In addition, 143 pC/N (∼4.5 times higher than commercial piezoelectric PVDF films) piezoelectric charge coefficient (d₃₃) magnitude and superior response time (t_r ∼ 8 ms) of this composite ferroelectret film enable the detection of different physiological signals such as coughing, pronunciation, and gulping behavior, making it a promising candidate for early intervention of healthcare, which may play a significant role in accurate alert of influenza and chronic obstructive pulmonary disease (COPD)-related symptoms. In addition, MEH enables the tracking of the subtle pressure change in the wrist pulse, indicating its usefulness in effective mechano-sensitivity. Since the cardiovascular signal is one of the vital parameters that can determine the on-going physiological conditions, the wireless transmission of the detected wrist pulse signal has been demonstrated. All of these features coupled with wireless data transmission indicate the promising application of MOF-assisted composite ferroelectret films in noninvasive real-time remote healthcare monitoring.

Electricity Generation through Light-Responsive Diving-Surfacing Locomotion of a Functionally Cooperating Smart Device

Mini-generators converting other forms of energy into electric energy are ideal power supplies for widely used microelectronic devices because they need only a low power supply in the range of µW to mW. Among various creative strategies to fabricate mini-generators, recently developed functionally integrated systems combining self-propulsion of small objects and the application of Faraday's law show advantages such as facile, noncontact, low resistance, and durability. However, wide application of such functionally integrated systems is currently restricted by artificial energy inputs, such as chemical fuels or mechanical work, and harvesting energy available in the environment or nature is urgently required. Herein, a light-responsive functionally cooperating smart device is developed as a mini-generator that can directly harvest naturally available light energy for diving-surfacing motions, thus converting mechanical energy into electricity through Faraday's law. The mini-generator generates a maximum voltage of 1.72 V with an energy conversion efficiency of 2.44 × 10-3 % to power LEDs and shows a lifetime of at least 30 000 s. By using environmental energy, the study may promote the concept of a functionally cooperating system as an economic and facile power supply for microelectronics, reducing their dependence on batteries.