Fabrication of Moisture-Responsive Crystalline Smart Materials for Water Harvesting and Electricity Transduction

Abstract

It is of profound significance with regard to the global energy crisis to develop new techniques and materials that can convert the chemical potential of water into other forms of energy, especially electricity. To address this challenge, we built a new type of energy transduction pathway (humidity gradients → mechanical work → electrical power) using moisture-responsive crystalline materials as the media for energy transduction. Single-crystal data revealed that a flexible zeolitic pyrimidine framework material, ZPF-2-Co, could undergo a reversible structural transformation (β to α phase) with a large unit cell change upon moisture stimulus. Dynamic water vapor sorption analysis showed a gate-opening effect with a steep uptake at as low as 10% relative humidity (RH). The scalable green synthesis approach and the fast water vapor adsorption–desorption kinetics made ZPF-2-Co an excellent sorbent to harvest water from arid air, as verified by real water-harvesting experiments. Furthermore, we created a gradient distribution strategy to fabricate polymer-hybridized mechanical actuators based on ZPF-2-Co that could perform reversible bending deformation upon a variation of the humidity gradient. This mechanical actuator showed remarkable durability and reusability. Finally, coupling the moisture-responsive actuator with a piezoelectric transducer further converted the mechanical work into electrical power. This work offers a new type of moisture-responsive smart material for energy transduction and provides an in-depth understanding of the responsive mechanism at the molecular level.

High Energy and Power Density Peptidoglycan Muscles through Super‐Viscous Nanoconfined Water

“…Recent demonstrations and theoretical predictions showed that such WR actuation could be extremely powerful and efficient, [7][8][9] inspiring the growing studies and development of WR structures for actuators and artificial muscles. [10][11][12][13][14][15][16][17] Notable WR examples include a titanium oxide film [18] and a twisted carbon nanotube yarn, [19] which exhibit WR energy densities of ≈1250 and 1800 kJ m −3 (2.17 kJ kg −1 ), respectively. Microrobots equipped with WR actuators of 𝜋-stacked carbon nitride films [8] and polyethylene oxide nanofibers [20] have been demonstrated to exhibit autonomous locomotion powered by fluctuations in ambient RH.…”

“…Recent demonstrations and theoretical predictions showed that such WR actuation could be extremely powerful and efficient, [ 7 , 8 , 9 ] inspiring the growing studies and development of WR structures for actuators and artificial muscles. [ 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 ]…”

Insights into the Effect of Trans-to-Cis Photoisomerization of a Co-coordinated Stilbene Derivative on the Luminescence of Di-β-diketonate Lanthanide Complexes

“…In recent years, smart materials have been studied extensively for their important applications in molecular switches, − white light-emitting diodes, − information storage, , anti-counterfeiting, , separation and detection, − drug delivery, , and other fields. − Smart material molecules can reversibly change their physical and chemical properties under different external stimuli. , Among various external stimuli, including light energy, electrical energy, and chemical energy, light is the most suitable and convenient source of clean energy and has advantages of precise control as a stimulus source and energy-saving and environmental protection characteristics. Previously reported light stimulation of smart molecules includes the trans-to-cis isomerization of azobenzene and stilbene derivatives, − photocyclization of diarylethylenes, − [2 + 2] cycloaddition of alkenes, − and [4 + 4] photodimerization of anthracene. − Photoinduced trans-to-cis isomerization has attracted much attention in inorganic and organic chemistry, materials science, and biology.…”

A Ti3C2Tx MXene-Based Energy-Harvesting Soft Actuator with Self-Powered Humidity Sensing and Real-Time Motion Tracking Capability

“…There are only a handful of piezoelectric actuators that can convert the chemical potential in humidity to pulse electricity in low efficiency. , However, the electricity generated is too weak to enable the sensing capability and communicating with external electrics unless applying rectifier circuits. The recent technology of moist-electric generation (MEG) provides the feasibility of generating electricity with high voltage from humidity by ionic diffusion in hydrophilic materials. ,,, Applying this concept to moisture-responsive soft actuators is promising in realizing not only electricity generation but also self-powered sensing of their actuating patterns and humidity, which, however, remains unexplored by far.…”

“…It is the only humidity-responsive actuator that can simultaneously harvest the humidity energy to mechanical power and electricity for enabling self-powered sensing of humidity and motion modes in real-time (Figure , Table S1). ,− ,− Such multiple functionalities are integrated into a polyethylene terephthalate (PET)-supported composite membrane (MCPM) of MXene, cellulose, and polystyrene sulfonic acid (PSSA) by directional proton diffusion and asymmetric expansion under moisture gradient (Figure a). The obtained soft actuator exhibits a maximum bending angle of 130 o , while generating the electricity with a maximum power density of 81.2 μW cm –3 and an open-circuit voltage ( V OC ) of 0.3 V. With these benefits, it can be used for developing not only power sources but also self-powered smart switches, soft robots, human-touching, and breathing monitors with high sensitivity.…”