Experimental Studies and Numerical Simulation of Polypyrrole Trilayer Actuators.

Conducting polymer actuators have shown wide application prospects in the field of biomedical sensors and micro-/nanorobotics. In order to explore more applications in biomedical sensing and robotics, it is essential to understand the actuator static behavior from an engineering perspective, before incorporating them into a design. In this article, we have established the mathematical model of a trilayer polypyrrole (PPy) cantilever actuator and validated it experimentally. The model helps in enhancing the efficiency and in improving the performance, predictability, and control of the actuator. The thermal expansion analogy, which is similar to volume change of the multilayer PPy actuator due to ion migration, has been considered to develop a mathematical model in COMSOL Multiphysics. To further validate the actuator deformation predicted by the mathematical modeling, a multilayer PPy actuator was fabricated by electrochemical synthesis and the experimentally determined deflection of the actuator was compared to simulation data. Both the theoretical and experimental results depict that the model is effective for predicting the bending behavior of multilayer PPy actuators at different input voltages.

All-reflective ring illumination system for photoacoustic tomography.

Given that breast cancer is the second leading cause of cancer-related deaths among women in the United States, it is necessary to continue improving the sensitivity and specificity of breast imaging systems that diagnose breast lesions. Photoacoustic (PA) imaging can provide functional information during in vivo studies and can augment the structural information provided by ultrasound (US) imaging. A full-ring, all-reflective, illumination system for photoacoustic tomography (PAT) coupled to a full-ring US receiver is developed and tested. The US/PA tomography system utilizes a cone mirror and conical reflectors to optimize light delivery for PAT imaging and has the potential to image objects that are placed within the ring US transducer. The conical reflector used in this system distributes the laser energy over a circular cross-sectional area, thereby reducing the overall fluence. This, in turn, allows the operator to increase the laser energy achieving better cross-sectional penetration depth. A proof-of-concept design utilizing a single cone mirror and a parabolic reflector is used for imaging cylindrical phantoms with light-absorbing objects. For the given phantoms, it has been shown that there was no restriction in imaging a given targeted cross-sectional area irrespective of vertical depth, demonstrating the potential of mirror-based, ring-illuminated PAT system. In addition, the all-reflective ring illumination method shows a uniform PA signal across the scanned cross-sectional area.

Titania, silicon dioxide, and tantalum pentoxide waveguides and optical resonant filters prepared with radio-frequency magnetron sputtering and annealing.

Mixing dielectric materials in solid-thin-film deposition allows the engineering of thin films' optical constants to meet specific thin-film-device requirements, which can be significantly useful for optoelectronics devices and photonics technologies in general. In principle, by use of radio-frequency (rf) magnetron sputtering, it would be possible to mix any two, or more, materials at different molar ratios as long as the mixed materials are not chemically reactive in the mixture. This freedom in material mixing by use of magnetron sputtering has an advantage by providing a wide range of the material optical constants, which eventually enables the photonic-device designer to have the flexibility to achieve optimal device performance. We deposited three combinations from three different oxides by using rf magnetron sputtering and later investigated them for their optical constants. Each two-oxide mixture was done at different molar ratio levels. Moreover, postdeposition annealing was investigated and was shown to reduce the optical losses and to stabilize the film composition against environmental effects such as aging and humidity exposure. These investigations were supported by the fabricated planar waveguides and optical resonant filters.