Stomata‐Inspired Membrane Produced Through Photopolymerization Patterning

Abstract

wileyonlinelibrary.com ( Figure 1 A-b). Stomata are tiny pores distributed on the leaf surface (Figure 1 A-a). A pair of guard cells open and close the stomata, which function as multisensory turgor-operative valves to exchange gases between a plant and its environment. [ 21 ] Biomimetic technologies, such as evaporative pumps and artifi cial leaves, have been developed based on the functional features of plant leaves. [22][23][24] Thus far, the advantageous features of stimuli-responsive opening or closing of stoma in a unique hydraulic valve have not been simulated.In this study, we demonstrate a novel approach to mimic the gating function of stomata by using a temperature-responsive hydrogel. A simple, cost-effective, and high-throughput photolithographic method was employed to pattern a large surface area in a controlled manner. [25][26][27] In contrast to previous works that fabricated hydrogel actuators which were mostly made with bilayers of different materials, [ 18,19 ] the present study used a single material to synthesize an actuating membrane through the polymerization-induced diffusion on the microscale surface of the polymerizing media. In this particular case, monomers and free radicals were diffused to opposite directions, depending on the chemical potential gradient of the polymerizing material. A distinct double part with pores was created within the polymer membrane by single illumination. Each part presents different mechanical functions on the morphological deformation of the membrane. The SIM shrinks to open the pores, similar to stomata, when triggered by a slight temperature change. The use of a single material in double-parted actuators eliminates any risk of delamination. In addition, the morphological confi guration of the SIM can be easily controlled by changing the photomask for a specifi c application. As the SIM utilizes high sensing-to-actuation functions of stimuli-responsive hydrogels and its fabrication is easy, this membrane can be used in numerous practical applications, including fi lter membranes with adjustable pore sizes, membrane-based sensors, smart valves, and membrane-based actuators. Results and DiscussionThe fabricated membranes contain gating pores that respond to simple temperature changes. A UV-curable poly( Nisopropylacrylamide) (PNIPAAm) hydrogel was used forThe programmed movements of responsive functional hydrogels have received much attention because of their abundant functions and wide range of engineering applications. In this study, an innovative stomata-inspired membrane (SIM) is fabricated by using a temperature-responsive hydrogel through a simple, cost-effective, and high-throughput patterned photopolymerization. Polymerization-induced diffusion on the macroscale surface results in formation of a double-parted polymer membrane with fi ne pores after single illumination. After heating the SIM, the less deformable thick frame supports the whole structure and the highly deformable thin base regulates pore shape. Among various SIM types, the slit pores of ...

Compact and Thermosensitive Nature-inspired Micropump

“…2b)27. On the surface of the SIM, water molecules accumulate in the rounded grooves of a hundred-nanometer scale and form air-water interfaces (Fig.…”

“…The water extrusion and absorption through the polymer network arises from the wettability change of PNIPAAm. The PNIPAAm becomes hydrophobic at temperatures higher than the LCST, and the material become hydrophilic at the temperature lower than the LCST27.…”

“…The pre-gel solution was covered with a transparent photomask on which the slit patterns were printed, and then irradiated with UV-light (VIRVER Lourmat-4.L, France; λ  = 365 nm, 4 W) for 4 min. These processes were sequentially conducted, as in our previous study27. The fabricated SIM was carefully peeled off from the photomask and applied to the agarose cryogel of the pump.…”

Nature-inspired thermo-responsive multifunctional membrane adaptively hybridized with PNIPAm and PPy

“…The wettability of the membranes also changed with temperature, which is due to the transition of the thermoresponsive wettability of PNIPAm from hydrophilic to hydrophobic. 41 The water flux through the MC-HM was smaller than that of the MC-PM. This effect results from the increase of hydraulic resistance due to deposition of the more densely crosslinked PPy network.…”

Pine cone scale-inspired motile origami

“…Stimuliresponsive hydrogels can change their shape, surface characteristics, solubility and form. These hydrogels have been used in various practical applications such as in drug delivery systems, cell culture, sensors, pumps and actuators [7][8][9][10][11] . They have been elaborately developed using various fabrication methods to broaden their applications 12,13 .…”