Transfer printing by kinetically switchable adhesion to an elastomeric stamp shows promise as a powerful micromanufacturing method to pickup microstructures and microdevices from the donor substrate and to print them to the receiving substrate. This can be viewed as the competing fracture of two interfaces. This paper examines the mechanics of competing fracture in a model transfer printing system composed of three laminates:  an elastic substrate, an elastic thin film, and a viscoelastic member (stamp). As the system is peeled apart, either the interface between the substrate and thin film fails or the interface between the thin film and the stamp fails. The speed-dependent nature of the film/stamp interface leads to the prediction of a critical separation velocity above which separation occurs between the film and the substrate (i.e., pickup) and below which separation occurs between the film and the stamp (i.e., printing). Experiments verify this prediction using films of gold adhered to glass, and the theoretical treatment extends to consider the competing fracture as it applies to discrete micro-objects. Temperature plays an important role in kinetically controlled transfer printing with its influences, making it advantageous to pickup printable objects at the reduced temperatures and to print them at the elevated ones.

Current methodologies used for the inference of thin film stress through curvature measurement are strictly restricted to stress and curvature states that are assumed to remain uniform over the entire film/substrate system. These methodologies have recently been extended to a single layer of thin film deposited on a substrate subjected to the non-uniform misfit strain in the thin film. Such methodologies are further extended to multi-layer thin films deposited on a substrate in the present study. Each thin film may have its own non-uniform misfit strain. We derive relations between the stresses in each thin film and the change of system curvatures due to the deposition of each thin film. The interface shear stresses between the adjacent films and between the thin film and the substrate are also obtained from the system curvatures. This provides the basis for the experimental determination of thin film stresses in multi-layer thin films on a substrate.

Current methodologies used for the inference of thin film stress through curvature measurements are strictly restricted to uniform film stress and system curvature states over the entire system of a single thin film on a substrate. By considering a circular multilayer thin film/substrate system subjected to nonuniform temperature distributions, we derive relations between the stresses in each film and temperature, and between the system curvatures and temperature. These relations featured a “local” part that involves a direct dependence of the stress or curvature components on the temperature at the same point, and a “nonlocal” part, which reflects the effect of temperature of other points on the location of scrutiny. We also derive relations between the film stresses in each film and the system curvatures, which allow for the experimental inference of such stresses from full-field curvature measurements in the presence of arbitrary nonuniformities. These relations also feature a “nonlocal” dependence on curvatures making full-field measurements of curvature a necessity for the correct inference of stress. The interfacial shear tractions between the films and between the film and substrate are proportional to the gradient of the first curvature invariant, and can also be inferred experimentally.

Coherent gradient sensing (CGS), a shear interferometry method, is developed to measure the full-field curvatures of a film/substrate system at high temperature. We obtain the relationship between an interferogram phase and specimen topography, accounting for temperature effect. The self-interference of CGS combined with designed setup can reduce the air effect. The full-field phases can be extracted by fast Fourier transform. Both nonuniform thin-film stresses and interfacial stresses are obtained by the extended Stoney’s formula. The evolution of thermo-stresses verifies the feasibility of the proposed interferometry method and implies the “nonlocal” effect featured by the experimental results.

We report in situ observation of wrinkles formation and evolution of Si nanoribbons with finite length on elastomeric substrate via white light interferometer. The wrinkle originates from the middle of the nanoribbon, propagates symmetrically to the two ends, and finally reaches the stable configuration. The wavelength and amplitude will increase abruptly when the released strain exceeds the critical value. The interface interaction between Si nanoribbons and elastomeric substrate plays the key role for wrinkles formation. We gratefully acknowledge the support from National Natural Science Foundation of China (Grant Nos. 10902059, 90816007, 10820101048, and 10832005) and Foundation for the Author of National Excellent Doctoral Dissertation of China (FANEDD) (No. 2007B30).

Applications of ferroelectric ceramics, ranging from components for sensors, memory devices, microelectromechanical systems, and energy convertors, all involve planar and rigid layouts. The brittle nature of such materials and their high-temperature processing requirements limit applications to devices that involve only very small mechanical deformations and narrow classes of substrates. Here, we report a strategy for integrating nanoribbons of one of the most widely used ferroelectric ceramics, lead zirconate titanate, in “wavy” geometries, on soft, elastomeric supports to achieve reversible, linear elastic responses to large strain deformations (i.e., stretchable properties), without any loss in ferroelectric or piezoelectric properties. Theoretical and computational analysis of the mechanics account for these characteristics and also show that the amplitudes of the waves can be continuously tuned with an applied electric field, to achieve a vertical (normal) displacement range that is near 1000 times larger than is possible in conventional planar layouts. The results suggest new design and application possibilities in piezoelectric devices.

This paper describes the mechanism of the rate-dependent adhesion for a transfer printing system. A cohesive element model accounting for the viscoelastic effect of the stamp reveals the evolution of the stress and the stress distributions as the peeling velocity increases. Experiments using Si ribbons separating from a wafer verify this prediction and demonstrate the influence of the rate-dependent effect on the transfer efficiency. The simulations show the relaxation time of the stamp has little effect on the transfer efficiency, and implies that it can be improved by adjusting the viscoelastic modulus.

Kinetically controlled transfer printing based on rate-dependent adhesion is widely used to heterogeneously integrate micro/nano-devices. Through analysis of peeling stamps with grating-like micropatterns from the rigid substrate in different directions, the directionally dependent adhesion strength is investigated in detail. Experiments of peel test and picking up silicon ribbons from silicon-on-insulator wafer were conducted and consistent with the analytical prediction. The method and analytical results proposed in this Letter can guide the design of the micropatterns on stamp to realize a more effective transfer printing approach. We gratefully acknowledge the support from National Natural Science Foundation of China (Grant Nos. 11222220, 90816007, 91116006, 10902059, and 11320101001) and Tsinghua University Initiative Scientific Research Program (Grant No. 2011Z02173).

Transfer printing is an exceptionally sophisticated approach to assembly and micro-/nanofabrication that relies on a soft, elastomeric ‘stamp’ to transfer solid, micro-/nanoscale materials or device components from one substrate to another, in a large-scale, parallel fashion. The most critical control parameter in transfer printing is the strength of adhesion between the stamp and materials/devices. Conventional peel tests provide effective and robust means for determining the interfacial adhesion strength, or equivalently the energy release rate, and its dependence on peel speed. The results presented here provide analytic solutions for tests of this type, performed using viscoelastic strips with and without patterns of relief on their surfaces, and validated by systematic experiments. For a flat strip, a simple method enables determination of the energy release rate as a function of the peel speed. Patterned strips can be designed to achieve desired interfacial properties, with either stronger or weaker adhesion than that for a flat strip. The pattern spacing influences the energy release rate, to give values that initially decrease to levels smaller than those for a corresponding flat strip, as the pattern spacing increases. Once the spacing reaches a critical value, the relief self-collapses onto the substrate, thereby significantly increasing the contact area and the strength of adhesion. Analytic solutions capture not only these behaviors, as confirmed by experiment, but also extend to strips with nearly any pattern geometry of cylindrical pillars.

Coherent gradient sensing (CGS) method, a real time, full-field optical technique, is insensitive to vibrations and able to provide slope and curvature maps and surface topographies, to investigate non-uniform deformations. In this paper, we analyze the thermal effects on the optical path in CGS due to air convection, and the influence of grating thickness and refractive index on the measurement accuracy. A modified governing equation is derived considering the grating thickness, which is demonstrated by testing a standard sample. Finally, we apply CGS method to measure the full-field deformation of a specimen at high temperature.