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For over a decade, microscopic devices which are propelled and therefore active versus inactive nanoparticles have emerged as versatile and novel tools for a variety of applications including environmental and in vivo. In this dissertation, we aim to demonstrate the recent advances in milli and microscale devices by utilizing new designs and especially new materials towards replicating biological functions, becoming more environmentally friendly and more useful in in vivo applications.In the first section we show how selecting the appropriate set of materials and incorporating them into the structure or on the outside of milli-sized devices can give them capabilities of color-change, self-healing, and birth-like release much like the real-life counterparts from which the inspiration came from.In the second section we demonstrate the ability to utilize materials which make micromotors not only able to move in biological fluids but become completely transient and disappear without a trace while at the same time studying their time-dependent motion behavior.The third section describes the use of transient type micromotors in biological settings. We utilize these micromotors to deliver important nutrients to treat anemia, deliver a vaccine and establish an immune response and implement them in standard pill formulations for further integration into common use.We hope that these developments will help and inspire the community towards implementing these microscale devices in many common applications and possibly disrupting current technologies in the near future.

Responsive photonic bandgap materials, more commonly known as responsive photonic crystals, which can remotely change their structural colors in response to the external stimuli, have important applications in areas such as color displays, biological and chemical sensors, inks and paints, or many optically active components. Despite the development of different types of colloidal responsive photonic systems, wide use of these systems in practical applications is hampered by low fabrication efficiency, limited tunability of the band gap, a slow response to the external stimuli, and difficulty of integration into existing photonic systems. Through the magnetic assembly route, we attempted to develop new types of responsive photonic nanostructures with improved fabrication efficiency, rapid response, and wide tunability of the band gap. We have demonstrated the rapid assembly of superparamagnetic colloidal particles into various photonic nanostructures. We have also demonstrated that an external magnetic field can be used as an effective stimulus to manipulate the photonic properties of the self-assembled nanostructures by affecting the lattice constant, the orientation, or the crystal structures. As there are many more choices for nonmagnetic colloidal particles with uniform size and optimal refractive index, it would be advantageous to extend this magnetic assembly strategy to nonmagnetic particles. We have demonstrated the use of nanocrystal-based ferrofluids to direct the assembly of nonmagnetic colloidal particles into photonic crystal structures. The process is general, efficient, convenient, and scalable and thus represents a new and practical platform for the fabrication of colloidal crystal-based photonic devices. We have also developed a universal strategy that allows convenient magnetically-driven assembly of general objects in defined locations with high spatial resolution. The process involves immersing a polymer relief pattern in a uniformly magnetized ferrofluid, which modulates the local magnetic fields around the pattern. Nonmagnetic target objects dispersed in the same ferrofluid can then be magnetically assembled at positions defined by the polymer pattern. As the nonmagnetic polymer patterns can be conveniently fabricated at low cost, our method provides a general yet very effective means to assemble a wide range of nanoscale objects, paving the way towards patterning functional microstructures.

The utilization of light to produce useful responses holds much potential for changing the world through smart materials and photovoltaic systems. We report the utilization of a variety of carbon nanotube composites as photovoltaic devices or as optothermal materials for the controlled placement of heat. Toward carbon nanotube - polymer photovoltaics we have successfully shown supramolecular compatibilization and functional bilayer devices. Opothermal processes are shown to manipulate a variety of system variables: surface energy, surface tension, and pressure. By manipulating these variables interesting responses are produced. Optothermal surface energy control produced wettability switches of 70º on composite surfaces. Optothermally modulated surface tensions of fluids converted light into work in the form of controlled linear motion, rotational motion, and volumetric expansion. Optothermally heated liquids confined within impermeable microcapsules resulted in the phototriggerable release of chemicals on demand. This release allowed small molecule reactions and polymerizations to be remotely initiated in a spatially selective manner. These results lay the framework for the expansion of the field of advanced optothermally responsive materials.