Stimuli-responsive surfaces with tunable fluidic and optical properties utilizing switchable surface topography are of significant interest for both scientific and engineering research. This work presents a surface involving silicon scales on a magnetically responsive elastomer micropillar array, which enables fluid and light manipulation. To integrate microfabricated silicon scales with ferromagnetic elastomer micropillars, transfer printing-based deterministic assembly is adopted. The functional properties of the surface are completely dictated by the scales with optimized lithographic patterns while the micropillar array is magnetically actuated with large-range, instantaneous, and reversible deformation. Multiple functions, such as tunable wetting, droplet manipulation, tunable optical transmission, and structural coloration, are designed, characterized, and analyzed by incorporating a wide range of scales (e.g., bare silicon, black silicon, photonic crystal scales) in both in-plane and out-of-plane configurations.

Although many recent studies demonstrate surfaces with switchable wettability under various external stimuli, a deliberate effort to self-propel liquid droplets utilizing a surface wetting mode switch between slippery lotus and adhesive rose petal states via a mechanical strain has not been made yet, which would otherwise further benefit microfluidic applications. In this work, we present a black silicon/elastomer (bSi/elastomer) composite surface which shows switchable wettability and adhesion across the two wetting modes by mechanical stretching. The composite surface is composed of a scale-like nanostructured silicon platelet array that covers an elastomer surface. The gap between the neighboring silicon platelets is reversibly changeable as a function of a mechanical strain, leading to the transition between the two wetting modes. Moreover, the composite surface is highly flexible although its wetting properties primarily originate from superhydrophobic bSi platelets. Different wetting characteristics of the composite surface in various mechanical strains are studied, and droplet manipulation such as droplet self-propulsion and pick-and-place using the composite surface is demonstrated, which highlights its potentials for microfluidic applications.

Enabling unique architectures and functionalities of microsystems for numerous applications in electronics, photonics and other areas often requires microassembly of separately prepared heterogeneous materials instead of monolithic microfabrication. However, microassembly of dissimilar materials while ensuring high structural integrity has been challenging in the context of deterministic transferring and joining of materials at the microscale where surface adhesion is far more dominant than body weight. Here we present an approach to assembling microsystems with microscale building blocks of four disparate classes of device-grade materials including semiconductors, metals, dielectrics, and polymers. This approach uniquely utilizes reversible adhesion-based transfer printing for material transferring and thermal processing for material joining at the microscale. The interfacial joining characteristics between materials assembled by this approach are systematically investigated upon different joining mechanisms using blister tests. The device level capabilities of this approach are further demonstrated through assembling and testing of a microtoroid resonator and a radio frequency (RF) microelectromechanical systems (MEMS) switch that involve optical and electrical functionalities with mechanical motion. This work opens up a unique route towards 3D heterogeneous material integration to fabricate microsystems.While monolithic microfabrication has been quite successful in the manufacturing of microsystems such as integrated circuits (IC) and microelectromechanical systems (MEMS) 1,2 , continued innovation towards three dimensional (3D) architectures and heterogeneous integration has been limited, which would otherwise enable improvements in performance and novel functionalities of microsystems. Associated challenges originate from layer-by-layer thin film processing on a single substrate and dissimilar nature of materials that may need different techniques to process. Consequently, 3D heterogeneous integration often requires independent fabrication of constituents followed by microassembly rather than monolithic microfabrication. In this context, transfer printing 3,4 has emerged as a method that utilizes highly reversible surface adhesion of a polymeric stamp to deterministically transfer microscale solid objects called "inks". The ability to transfer inks from a donor substrate where inks are grown and processed to a receiving substrate where inks are finally assembled reduces the complexity of manufacturing processes regarding heterogeneous material integration. Furthermore, previously reported micro-masonry 5 which relies on transfer printing demonstrates that after proper thermal processing, direct bonding between transferred silicon inks can be achieved, which may be sufficiently strong to produce various MEMS devices 6-8 . However, limited assembling material classes and quantitatively unknown interfacial characteristics between joined inks suppress broader adaptation of this transfer printing-based microasse...

This thesis presents the design, analytical and numerical modeling, fabrication and characterization of a hybrid tip-tilt-piston micromirror driven by electrostatic actuation. The micromirror involves a single crystal silicon mirror and a conductive elastomeric universal joint which are mechanically bonded and electrically interconnected. This device takes advantage of two distinct materials to achieve a high quality reflective surface using single crystal silicon and a highly flexible joint using an elastomer. To realize this hybrid system, micro-masonry techniques are employed such that silicon and elastomer parts are fabricated separately and integrated afterwards. The static and dynamic behaviors of the micromirror are characterized, indicating identical response about its two orthogonal scanning axes. Furthermore, the piston stroke utilized by the compressive deformation of the elastomeric joint along z-axis is investigated.iii

 Soft composite films are fabricated by transfer printing silicon ribbons onto elastomeric films in a spatially organized manner.  Tension-induced corrugation on the soft composite film is experimentally observed.  Corrugation amplitude in response to applied stretch is characterized.  Mechanism of corrugation formation on the composite film is elucidated by transformation rule.  Effect of design parameters on corrugation is experimentally and numerically investigated.