Switchable adhesives using stimuli-responsive systems have many applications, including transfer printing, climbing robots, and gripping in pick and place processes. Among these adhesives, electroadhesive surface can spontaneously adjust their adhesion in response to an external electric field. However, electroadhesives usually need high voltage (e.g. kV) and the adhesion disappears upon turning off the signal. These limitations make them complicated and costly. In this research, we demonstrated a gold-coated silica microsphere (GCSM) with highly switchable and memorable adhesion triggered by a relatively small voltage (<30 V). In the experiment, a silica microsphere with a diameter of 15 μm was glued to a tipless atomic force microscope (AFM) cantilever. The nanoscale thick gold coating was sprayed on the surface of the microsphere by a sputter coater. AFM was used to explore the tunable adhesion with an external voltage at different relative humidity (RH). The results revealed that when applying a positive electrical bias at high RH, the adhesive force increased dramatically while it decreased to almost zero after applying a negative potential. Even if the bias was turned off, the adhesive force state could still be kept and erased on demand by simply applying a negative voltage. The adhesive force can be altered repeatedly by an alternative electrical bias. This adhesion modulated by the external electrical signals is attributed to the electrochemical effect of the nanoscale-thick gold coating, where an oxide layer can be formed and thus becomes positively charged when applying a positive voltage, and counter electric field cancel out the applied negative voltage to decrease the adhesion force.

Advanced optical imaging techniques are emerging as useful ways to screen tissues for the presence of cancer. Plasmon resonant nanoparticles have unique optical properties that make them ideal for use as optical contrast agents. The capacity of these particles to serve a multifunctional role dependent on their composition and the intensity of incident light enables them to serve as diagnostic tools and to provide the therapeutic capability of photo-thermal energy conversion or the controlled release of an encapsulated agent. Likewise, the ability to degrade into components of a clearable size may enable the clinical translation of these types of particles.These properties were demonstrated by means of experiments in the support of three specific aims. The first specific aim was to determine whether the unique and tunable optical properties of nanorods lend them to generate signal in advanced optical imaging techniques, and that nanorods can facilitate photo-thermal conversion. The second specific aim was to show that liposomes can serve as a scaffold for the support of an array of gold nanodots to generate a structure that exhibit tunable plasmon resonant characteristics and a resultant ability to generate signal in optical imaging techniques while having the capability to degrade into inert particles of a size that can be readily cleared from the body via the kidney. The final specific aim was to determine whether the gold-coated liposomes of the second specific aim can serve as system for light-based delivery of an encapsulated agent in addition to its role as an optical contrast agent and its biodegradation capacity.Plasmon resonant nanorods and plasmon resonant gold-coated liposomes were generated by reducing free gold from solution onto surfactant coated seed particles and phospholipid liposomes, respectively. Both structures demonstrated the ability to generate signal in optical coherence tomography and in multi-photon confocal microscopy images. Nanorods in high intensity light demonstrate a capacity to mediate photo-thermal energy conversion. While, in similar conditions, gold-coated liposomes are shown to release their contents. Gold-coated liposomes are also shown to degrade to bioinert components of a size reasonable for rapid renal clearance using either surfactant or enzyme.

The purpose of these experiments was to determine the degradation mechanisms of molybdenum based field emitter arrays to oxygen exposures and to improve the overall reliability. In addition, we also evaluated the emission current stability of gold-coated field emitter arrays to oxygen exposures. oxygen at 1x10-6 torr was introduced into the chamber through a leak valve for different lengths of time and duty cycles. To ensure identical oxygen exposure and experimental measurement conditions, tips on half the area of the FEA were fully coated with gold and the other half were left uncoated. The emission current from the gold coated half was found to degrade much less than that from the uncoated half, in the presence of oxygen. Also in the absence of oxygen, the emission current recovery for the gold-coated side was much quicker than that for the uncoated side.

Novel biocompatible nanoprobes for optical imaging of Epidermal Growth Factor receptor (EGFR) were created. 5 and 18 nm gold nanoparticles (AuNPs) and 5 and 45 nm diameter silver nanoparticles (AgNPs) were conjugated to EGF protein via ?-lipoic acid. AgNPs were not previously attached to EGF. TOF-MS confirms EGF-linker formation. ELISA verifies the linked-EGF activity alone and with EGF-NPs. Core-shell silver-gold nanoparticles (AgAuNPs) gave similar results. TEM staining with uranyl acetate exhibits a bright ring, smaller than EGF, around nanoparticles. Dark field microscopy shows localized, intense cytoplasmic scattering, possibly lipid droplets, in cancer cells incubated with or without nanoprobes. Following injection, mice organs were harvested for EGF-NP immune response determination. Sterilization likely inactivated EGF before ICP-MS. Intense surface enhanced Raman scattering (SERS, 632.8 nm) follows MgSO4 induced EGF-AgNPs aggregation. Pelleted EGF-AgNP tagged cancer cells lack SERS indicative intensity contrast. AgAuNPs could provide increased stability, brighter SERS, and reduced silver biocompatibility concerns.