Thermophysical Properties Research Literature Retrieval Guide Edited by Y. S. Touloukian, J. K. Gerritsen and N. Y. Moore Second edition, revised and expanded. Book 1: Pp. xxi + 819. Book 2: Pp.621. Book 3: Pp. ix + 1315. (New York: Plenum Press, 1967.) n.p.

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Heat and Mass Transfer

This review comprises a detailed survey of ongoing methodologies for soft actuators, highlighting approaches suitable for nanometer- to centimeter-scale robotic applications. Soft robots present a special design challenge in that their actuation and sensing mechanisms are often highly integrated with the robot body and overall functionality. When less than a centimeter, they belong to an even more special subcategory of robots or devices, in that they often lack on-board power, sensing, computation, and control. Soft, active materials are particularly well suited for this task, with a wide range of stimulants and a number of impressive examples, demonstrating large deformations, high motion complexities, and varied multifunctionality. Recent research includes both the development of new materials and composites, as well as novel implementations leveraging the unique properties of soft materials.

Soft Actuators for Small-Scale Robotics.

Stimulus-responsive shape memory materials: A review

Fundamental issues related to flow boiling in minichannels and microchannels

Flow boiling in small hydraulic diameter channels is becoming increasingly important in many diverse applications. The previous studies addressing the effects of the channel size on the flow patterns, and heat transfer and pressure drop performance are reviewed in the present paper. The fundamental questions related to the presence of nucleate boiling and characteristics of flow boiling in microchannels and minichannels in comparison to that in the conventional channel sizes (3 mm and above) are addressed. Also, the effect of heat exchanger configuration—single-channel and multichannel—on the heat transfer and pressure drop performance is reviewed. The areas for future research are identified.

Heat transfer and pressure drop in narrow rectangular channels

Manufacturing issues related to a thin film NiTi shape memory alloy (SMA) microactuator (i.e. microwrapper) have been investigated using both wet and dry etching techniques. Results show that wet etching the amorphous film produces a cleaner pattern than the crystallized film. Transformation temperatures are not affected by the pre-exposure of the NiTi film to air before crystallization. However, this process produces breakage in the NiTi film at sacrificial layer steps. This is believed to be due to residual stresses developed between the film and substrate during sputtering. The film breakage is overcome by dry etching the film with an ion-milling technique. Curvature in the microwrapper arms is induced using either a bi-layer material (i.e. polyimide and NiTi) or a functionally gradated NiTi film. Results show that when heated the microwrapper arms flatten due to shape memory effect and curl up to form a cage-like structure when cooled.

Manufacturing issues of thin film NiTi microwrapper

Barium titanate (BaTiO{sub 3}) thin films that were derived from methoxypropoxide precursors were deposited onto (100) Si, Pt/Ti/SiO{sub 2}/(100) Si, and molecular-beam-epitaxy-grown (MBE-grown) (100) BaTiO{sub 3} on (100) Si substrates by spin coating. The crystallization behavior of the amorphous-gel films was characterized using in-situ transmission electron microscopy heating experiments, glancing-angle X-ray diffraction, and differential thermal analysis/thermogravimetric analysis. Amorphous-gel films crystallized at a temperature of {approximately}600 C to an intermediate nanoscale (5--10 nm) barium titanium carbonate phase, presumably BaTiO{sub 2}CO{sub 3}, that subsequently transformed to nanocrystalline (20--50 nm) BaTiO{sub 3}. Random nucleation in the bulk of the gel film was observed on all substrates. In addition, oriented growth of BaTiO{sub 3} was concurrently observed on MBE-grown BaTiO{sub 3} on (100) Si. High-temperature decomposition of the intermediate carbonate phase contributed to nanometer-scale residual porosity in the films. High concentrations of water of hydrolysis inhibited the formation of the intermediate carbonate phase; however, these sols precipitated and were not suitable for spin coating.

In–Situ Transmission Electron Microscopy Crystallization Studies of Sol–Gel‐Derived Barium Titanate Thin Films

Microstructural development of thin-film barium strontium titanate (Ba x Sr 1-x TiO 3 ) as a function of strontium concentration and thermal treatment were studied, using transmission electron microscopy (TEM) and X-ray diffractometry (XRD). Thin films, ∼250 nm thick, were spin-coated onto Pt/Ti/SiO 2 /Si substrates, using methoxypropoxide alkoxide precursors, and crystallized by heat-treating at 700°C. All films had the cubic perovskite structure, and their lattice parameters varied linearly with strontium content. Films with higher strontium concentrations had a larger average grain size. In situ TEM heating experiments, combined with differential thermal analysis/thermogravimetric analysis results, suggest that the gel films crystallize as an intermediate carbonate phase, Ba x Sr 1-x TiO 2 CO 3 (with a solid solution range from x = 1 to x = 0). Before decomposition at 600°C, this carbonate phase inhibits the formation of the desired perovskite phase.

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Crystallization of Sol–Gel-Derived Barium Strontium Titanate Thin Films

A composition for enhanced heat transfer fluid performance,comprising a base heat transfer fluid and a nanometer sized phasechange material. Introduction of nanometer sized phase changematerial into the heat transfer fluid leads to improved, highreversible thermal transport properties at elevated temperatureswhile ensuring low viscosity of the fluid at sub-freezingtemperatures. A method for preparing of the heat transfer fluidwith enhanced heat transfer performance, comprising making nanometersized capsules having the phase change material contained thereinand dispersing the capsules into the base heat transfer fluid.

Leslie A. Momoda

Papers

Heat transfer and pressure drop in narrow rectangular channels

Manufacturing issues of thin film NiTi microwrapper

In–Situ Transmission Electron Microscopy Crystallization Studies of Sol–Gel‐Derived Barium Titanate Thin Films

Crystallization of Sol–Gel-Derived Barium Strontium Titanate Thin Films

Nanometer sized phase change materials for enhanced heat transfer fluid performance