A transparent polymeric flexure-hinge nanopositioner, actuated by a piezoelectric stack actuator.

Nanopositioning using piezoelectric actuation and a flexure mechanism is one of most common methods for nanometre-scale positioning. Generally, flexure mechanism nanopositioners have been made from metal. Thus, their application to various environments needs careful consideration with regard to corrosion and circumference interference. In this study, we propose the concept of a chip-like polymeric flexure-based nanopositioner equipped with piezoelectric actuation. In its design, motion performance was predicted using finite element analysis of deformation and stress, and injection mouldability was considered through an injection moulding simulation to allow for fabrication by injection moulding. A cyclic olefin copolymer nanopositioner was fabricated using a mesoscale injection moulding process. Experiments demonstrated that the developed nanopositioner had a travel range of 15 µm with high linearity and it could be successfully controlled by a proportional-integral-derivative (PID) algorithm including a low-pass filter with a root mean square control error of 3 nm.

Microinjection Molding of Out-of-Plane Bistable Mechanisms.

We present a novel fabrication technique of a miniaturized out-of-plane compliant bistable mechanism (OBM) by microinjection molding (MM) and assembling. OBMs are mostly in-plane monolithic devices containing delicate elastic elements fabricated in metal, plastic, or by a microelectromechanical system (MEMS) process. The proposed technique is based on stacking two out-of-plane V-beam structures obtained by mold fabrication and MM of thermoplastic polyacetal resin (POM) and joining their centers and outer frames to construct a double V-beam structure. A copper alloy mold insert was machined with the sectional dimensions of the V-beam cavities. Next, the insert was re-machined to reduce dimensional errors caused by part shrinkage. The V-beam structure was injection-molded at a high temperature. Gradually elongated short-shots were obtained by increasing pressure, showing the symmetrical melt filling through the V-beam cavities. The as-molded structure was buckled elastically by an external-force load but showed a monostable behavior because of a higher unconstrained buckling mode. The double V-beam device assembled with two single-molded structures shows clear bistability. The experimental force-displacement curve of the molded structure is presented for examination. This work can potentially contribute to the fabrication of architected materials with periodic assembly of the plastic bistable mechanism for diverse functionalities, such as energy absorption and shape morphing.