Prescribing patterns in growing tubular soft matter by initial residual stress.

Initial residual stress is omnipresent in biological tissues and soft matter, and can affect growth-induced pattern selection significantly. Here we demonstrate this effect experimentally by letting soft tubes grow in the presence or absence of initial residual stress and by observing different growth pattern evolutions. These experiments motivate us to model the mechanisms at play when a growing bilayer tubular organ spontaneously displays buckling patterns on its inner surface. We demonstrate that not only differential growth, geometry and elasticity, but also initial residual stress distribution, exert a notable influence on these pattern phenomena. Prescribing an initial residual stress distribution offers an alternative or a more effective way to implement pattern selection for growable bio-tissues or soft matter. The results also show promise for the design of 4D bio-mimic printing protocols or for controlling hydrogel actuators.

Microstructured elastomeric surfaces with reversible adhesion and examples of their use in deterministic assembly by transfer printing.

Reversible control of adhesion is an important feature of many desired, existing, and potential systems, including climbing robots, medical tapes, and stamps for transfer printing. We present experimental and theoretical studies of pressure modulated adhesion between flat, stiff objects and elastomeric surfaces with sharp features of surface relief in optimized geometries. Here, the strength of nonspecific adhesion can be switched by more than three orders of magnitude, from strong to weak, in a reversible fashion. Implementing these concepts in advanced stamps for transfer printing enables versatile modes for deterministic assembly of solid materials in micro/nanostructured forms. Demonstrations in printed two- and three-dimensional collections of silicon platelets and membranes illustrate some capabilities. An unusual type of transistor that incorporates a printed gate electrode, an air gap dielectric, and an aligned array of single walled carbon nanotubes provides a device example.

Thickness-twist and face-shear waves in piezoelectric plates of monoclinic crystals.

We study the propagation of thickness-twist and face-shear waves in piezoelectric plates of monoclinic crystals, which include rotated Y-cut quartz and langasite as special cases. The equations of linear piezoelectricity are used. Exact solutions are obtained for both fully-electroded and unelectroded plates. Dispersion relations are plotted for both AT-cut quartz and Y-cut langasite plates. The difference in frequencies between the exact piezoelectric solutions obtained in the present paper and the approximate elastic solutions in the literature is found to be of the order of 1%, which is significant in acoustic wave resonator and sensor applications.

Theoretical modeling of frequency-dependent magnetoelectric effects in laminated multiferroic plates.

The recently derived 2-D equations for extensional, flexural, and thickness-shear motions of laminated plates of piezoelectric/piezomagnetic layers are employed in the analysis of the frequency dependence of magnetoelectric couplings in laminated plates of piezoelectric and piezomagnetic layers driven by time-harmonic magnetic fields. Four structures are analyzed. Two are symmetric about the middle plane and are for extensional motions. The other 2 are antisymmetric about the middle plane and are for flexural motions. Frequency-dependent magnetoelectric effects are calculated and compared. Near resonances, the time-dependent magnetoelectric coupling coefficients are found to be much larger than the static magnetoelectric coupling coefficients.