Tailoring Multistimuli Responsive Micropatterns Activated by Various Mechanical Modes

Abstract

A versatile wrinkle‐based micropatterned system with a film‐substrate structure is proposed, which contains a hydrophilic film of polyvinyl alcohol or its composite with laponite and a hydrophobic substrate of polydimethylsiloxane or its composite with carbon black. The wrinkled system features high design flexibility and multistimuli responsiveness, which can be activated by various mechanical methods, including vertical press or scratch, gentle stretch‐and‐release, bend, or analogous magneto‐mechanical and electro‐mechanical modes. The resultant wrinkles possess 1) instantaneous and reversible strain/moisture/light responsive optical modulation; 2) tunable dynamics for the aforementioned strain/moisture/light response;3) tailorable amplitude/wavelength; 4) unique surface morphologies from the coupling of wrinkles and cracks; 5) excellent reversibility and durability. A variety of applications are demonstrated based on this system, including 1) a moisture erasable highly sensitive pressure responsive device and pattern replicator with a high fidelity; 2) a moisture erasable scratch/magneto‐mechanical re‐writable tablet; 3) an electro‐mechanical controllable smart window with an ultra‐sensitive strain responsive transmittance modulation and a low operating voltage; 4) various types of strain responsive, moisture erasable, and laser writable information recording/encryption devices. This work provides new routes for designing innovative wrinkled systems triggered by diverse mechanical fashions and can decode multiple environmental stimuli into optical signals for widespread application.

Dynamic multifunctional devices enabled by ultrathin metal nanocoatings with optical/photothermal and morphological versatility

“…2 C , the “UCONN” logo background was originally visible through the device at a released state. Upon stretching to 25.0% strain, the logo became obscured, which can be attributed to the formation of mechanical-responsive micro-/nanotopographies, especially wrinkles, that dramatically changed the light-scattering properties ( Movie S2 ) ( 24 , 48 ). Fig.…”

“…67,000 and a degree of hydrolysis of 88%. Here, the application of PVA with a low degree of hydrolysis makes the film highly sensitive to moisture ( 17 , 24 ). Thereafter, the remaining wrinkles on the PVA film can be completely erased by moisture as the internal stress of the highly hydrophilic PVA molecular chains can be released by moisture.…”

“…Smart or stimuli-responsive materials have controllable optical, mechanical, electronic, and/or other properties that can be effectively converted by external stimuli, such as mechanical force ( 1 – 13 ), light ( 14 – 18 ), temperature ( 11 , 18 – 20 ), moisture ( 17 , 21 – 23 ), electricity ( 24 – 27 ), and so on ( 13 , 27 – 30 ). One of the major efforts in this field is to mimic the intriguing micro-/nanotopographies of numerous organisms, which serve various functions in nature.…”

“…These disadvantages severely restrain the fabrication of thin films in submicro-/nanoscale dimensions and limit the generation of corresponding micro-/nanomorphologies, which are essential to develop new morphology-driven multifunctional devices. For instance, when a polymer-based thin film is used in a bilayer system, it is hard to decrease the average intercrack spacing to <30 μm ( 3 , 35 , 36 ) or lower the wavelength of wrinkles to <3 μm ( 17 , 21 , 24 , 37 , 38 ), which typically requires a very low film thickness (<30 nm) to achieve such a low intercrack spacing and wrinkle wavelength. Also, in a polymer-based film system, it is very challenging to precisely tailor the optical reflectance, transmittance, and photothermal effect when the thin film is <30 nm in thickness.…”

Single metal-organic framework–embedded nanopit arrays: A new way to control neural stem cell differentiation

“…First, nMOF, termed nUiO-67, was synthesized and characterized for stable RA storage and long-term release (>26 days). Thereafter, to prevent any physical interaction between the cells and nUiO-67 and to enhance cellular adhesion on substrates, large-scale homogeneous nanopit arrays were generated using laser interference lithography (LIL) (33)(34)(35)(36)(37). By adjusting the size of the nanopits to approximately 450 nm with a 250 nm gap distance (L hole /L pitch = 0.64) and considering the diameter of nUiO-67 as approximately 177 nm, we can confine one nanopit with one nUiO-67 nanoparticle with 98.3% loading efficiency.…”