Self‐assembled membranes with periodic wrinkled patterns are the critical building blocks of various flexible electronics, where the wrinkles are usually designed and fabricated to provide distinct functionalities. These membranes are typically metallic and organic materials with good ductility that are tolerant of complex deformation. However, the preparation of oxide membranes, especially those with intricate wrinkle patterns, is challenging due to their inherently strong covalent or ionic bonding, which usually leads to material crazing and brittle fracture. Here, wrinkle‐patterned BaTiO3 (BTO)/poly(dimethylsiloxane) membranes with finely controlled parallel, zigzag, and mosaic patterns are prepared. The BTO layers show excellent flexibility and can form well‐ordered and periodic wrinkles under compressive in‐plane stress. Enhanced piezoelectricity is observed at the sites of peaks and valleys of the wrinkles where the largest strain gradient is generated. Atomistic simulations further reveal that the excellent elasticity and the correlated coupling between polarization and strain/strain gradient are strongly associated with ferroelectric domain switching and continuous dipole rotation. The out‐of‐plane polarization is primarily generated at compressive regions, while the in‐plane polarization dominates at the tensile regions. The wrinkled ferroelectric oxides with differently strained regions and correlated polarization distributions would pave a way toward novel flexible electronics.

The integration of ferroic oxide thin films into advanced flexible electronics will bring multifunctionality beyond organic and metallic materials. However, it is challenging to achieve high flexibility in single-crystalline ferroic oxides that is considerable to organic or metallic materials. Here, we demonstrate the superior flexibility of freestanding single-crystalline BiFeO3 membranes, which are typical multiferroic materials with multifunctionality. They can endure cyclic 180° folding and have good recoverability, with the maximum bending strain up to 5.42% during in situ bending under scanning electron microscopy, far beyond their bulk counterparts. Such superior elasticity mainly originates from reversible rhombohedral-tetragonal phase transition, as revealed by phase-field simulations. This study suggests a general fundamental mechanism for a variety of ferroic oxides to achieve high flexibility and to work as smart materials in flexible electronics.

The solubility behavior of three high-melting fats (tripalmitin sample, PPP-S; cocoa butter-stearin, CB-S; and palm oil-stearin, PO-S) in five low-melting fats (tricaprylin, CCC; canola oil; sunflower oil; lard-olein, LD-O; and palm oil-olein, PO-O) was studied. To create the solubility curve, the high-melting fat was first equilibrated in the low-melting model lipid system between 25 and 62.5°C for 1 wk. The amount of high-melting fat dissolved in the low-melting model lipid system was then determined by analyzing TAG compositions in the liquid phase using GC. The low-melting CCC formed partial solid solutions with each of the high-melting fats as a result of its very short chain length. PPP-S formed an ideal solution in all of the low-melting fats except CCC. The mixtures of CB-S/LD-O, CB-S/PO-O, and PO-S/LD-O deviated from ideality, illustrating closer interactions between TAG from CB-S and PO-S and those from LD-O or PO-O. The melting temperature and heat of fusion of the high-melting fats calculated from the Hildebrand equation was very close to those determined by DSC. Paper no. J11292 in JAOCS 83, 505-511 (June 2006).

Lateral force microscopy (LFM) was used to image patterned organic surfaces and showed consistent changes in image contrast with surface composition. Self-assembled monolayers (SAMs) of ω-substituted alkanethiolates were patterned on surfaces of gold films coated on silicon wafers. The patterns consisted of areas of gold modified by SAMs formed from dodecanethiol (HS(CH2)11CH3) and areas derivatized by mixed SAMs formed by exposure to solutions of mixtures of HS(CH2)11CH3 and hexaethylene glycol-terminated alkanethiol [HS(CH2)11(OCH2CH2)6OH]. Several types of patterned SAMs were investigated, each of which differed in the relative mole fractions of methyl- and hexaethylene glycol-terminated alkanethiolates in the mixed SAMs. Analysis of the relative friction measured for the different mixed SAMs suggests that LFM can be used as a semiquantitative technique for compositional mapping of mixed SAMs. Correlation between relative friction and the composition (as estimated by X-ray photoelectron spectroscopy) and the wettability of mixed monolayers are presented for the types of SAMs investigated. The friction is directly proportional to the fraction of hexaethylene glycol-terminated alkanethiolates present in the mixed SAMs. The correlations can be applied in the semiquantitative estimation of the compositional and wetting properties of microscopic patterns in the mixed SAMs. As an example, we have used the compositional correlation together with LFM imaging to estimate the degree of displacement of an hexaethylene glycol-terminated SAM by a microdroplet of HS(CH2)11CH3.

No abstract