Reversible Humidity Sensitive Clothing for Personal Thermoregulation.

Two kinds of humidity-induced, bendable smart clothing have been designed to reversibly adapt their thermal insulation functionality. The first design mimics the pores in human skin, in which pre-cut flaps open to produce pores in Nafion sheets when humidity increases, as might occur during human sweating thus permitting air flow and reducing both the humidity level and the apparent temperature. Like the smart human sweating pores, the flaps can close automatically after the perspiration to keep the wearer warm. The second design involves thickness adjustable clothes by inserting the bent polymer sheets between two fabrics. As the humidity increases, the sheets become thinner, thus reducing the gap between the two fabrics to reduce the thermal insulation. The insulation layer can recover its original thickness upon humidity reduction to restore its warmth-preservation function. Such humidity sensitive smart polymer materials can be utilized to adjust personal comfort, and be effective in reducing energy consumption for building heating or cooling with numerous smart design.

Controlled metallic nanopillars for low impedance biomedical electrode.

Radial metallic nanopillar/nanowire structures can be created by a controlled radiofrequency (RF) plasma processing technique on the surface of certain alloy wires, including important biomedical alloys such as MP35N (Co-Ni-Cr-Mo alloy), platinum-iridium and stainless steel. In electrode applications such as pacemakers or neural stimulators, the increase in surface area in elongated MP35N nanopillars allows for decreased surface impedance and greater current density. However, the nanopillar height on MP35N alloy tends to be self-limiting at ∼1-3µm. The objective of this study was to further elongate the radial nanopillars so as to reduce electrode impedance for biomedical electrode applications. Intelligent experimental design allowed for efficient investigation of processing parameters, including plasma material, process duration, power, pressure and repetition. It was found that multi-step repeated processing in the parameter-controlled RF environment could increase nanopillar height to ∼10µm, a 400% improvement, while the RF plasma processing with identical total duration but in a single step did not lead to desired nanopillar elongation. Measurement of electrode impedance in phosphate-buffered saline solution showed an associated decrease to one-fifth of the surface impedance of unprocessed wire for signals below 100Hz. For the purposes of this study, MP35N and Pt-Ir wires were characterized and demonstrated augmented surface impedance properties which, in combination with superior cell integration, enhanced biomedical electrode performance.