The objective of this study was to present a rotary manipulating system driven by a rotary actuator based on twisted shape memory alloy (SMA) wires. The rotary actuator was composed of two oppositely twisted SMA wires connecting a rotor and a stator through a shaft. Two oppositely twisted SMA wires could generate bidirectional rotary motions upon actuation of each twisted SMA wire corresponding to the direction against the twist direction of each SMA wire. A manipulator was designed and fabricated by integrating manipulating arms, the rotary actuator, and a Hall effect magnetic rotary encoder which could measure the angular position of the rotary motion. We modeled and characterized the manipulator upon application of a ramp current input to each twisted SMA wire. A proportional-integral-derivative (PID) controller was designed and implemented to control the proposed rotary manipulator. Reference angular position tracking performances of the manipulator were evaluated with a series of experiments.

Shape memory alloy (SMA) has been widely used for many engineering and scientific applications, because it is largely deformable with high power density, and can be actuated easily by resistive heating. It is possible to reduce the size of the actuators by integrating or embedding SMA into the structures. While many applications have been reported regarding linear or bending actuators using the SMA wire, the development of a rotary actuator remains important and challenging for the engineering applications. Here, a new type of millimeter-scale rotary actuator is proposed based on the twisted SMA wires. SMA wires are twisted, folded, and integrated into the rotary actuator, and simple change of the twist direction enables the rotary actuator to rotate in the opposite direction. By integrating the oppositely twisted SMA wires into one rotary actuator unit, bidirectional rotary motions are possible. The actuation mechanism, design, and fabrication processes of the proposed rotary actuator are presented and demonstrated with its actuation performance. The fabricated actuators had average rotary working ranges from -38.68±4.92 deg to +45.37±8.79 deg in counterclockwise (CCW) and clockwise (CW) directions. This study will leverage the practical advances in the relevant engineering and scientific applications.

Recent developments in additive manufacturing (AM) process have led us to fabricate many mechanical and electrical components or devices into complex geometries. Within existing AM processes, laser is widely used as an energy source to selectively sinter particles with a powder bed fusion (PBF) process or cure photopolymers with a vat photopolymerization (VPP) process. This study investigated the applicability of the SLS process for silver nanoparticles (Ag NPs)-photopolymer inks to fabricate micro-scale conductive patterns. With Ag NPs-photopolymer inks prepared with different mixture ratios and pasted on a polyethylene terephthalate (PET) substrate, a pulse width modulation (PWM) signal-controlled 405 nm laser was applied to these inks to selectively sinter and cure the Ag NPs and the photopolymer simultaneously. The final conductive patterns were obtained after a rinse in ethanol to remove un-sintered and un-cured regions of the inks. Microstructures, thickness profiles, pattern width, electrical resistance, and resistivity of the fabricated patterns were investigated by varying the PWM duty and the laser exposure time. Effects of different numbers of scan lines in the pattern and nanoparticle mixture ratios were also investigated. The proposed method is cost effective and easy with fast patterning capabilities. It will leverage practical advances in AM industries.

Characteristics of off-grid hybrid renewable energy sources for high mountain villages are discussed. Considering reliability of electric power generation, Photovoltaic (PV)-wind hybrid and PV-hydro hybrid system are suggested. Connecting two or more villages with these hybrid systems, an extended hybrid off-grid can be formed. Sustainability of entire system is important in design of off-grid system, and income generation of the village people using the electricity should be considered.