Using light to control the interactions between self-rotating assemblies of active gels

Polymer gels undergoing the oscillating Belousov-Zhabotinsky (BZ) reaction exhibit an autonomous, periodic swelling and deswelling, where the mechanical oscillations are driven by the chemical reaction within the polymer network. Using computer simulations, we show that these BZ gels can undergo a form of auto-chemotaxis, enabling the gels to spontaneously move in response to self-generated chemical gradients. Focusing on four millimeter-sized pieces of these BZ gels, we show that the pieces can organize into self-rotating clusters that resemble a moving pinwheel or gear. By analyzing the factors that promote the formation of a single self-rotating cluster, we attempt to design systems of multiple, interacting gears. We show that light, which suppresses the oscillations of the gels, can be harnessed to promote the formation of two self-rotating clusters. These studies point to a novel form of photo-chemo-mechanical transduction, where light is utilized to control the conversion of chemical and mechanical energy in the system. Moreover, the interaction between the BZ gel gears reveals a new form of entrainment between these moving units. Namely, their coordinated motion is achieved through chemical coupling or communication, rather than a mechanical coupling. These findings can lead to the formation of chemically “communicating” devices that can be programmed to perform autonomous work through the use of light.     

快速响应智能水凝胶的研究进展

能响应外界刺激的智能水凝胶由于其特有的响应性,具有广泛的应用前景。做为药物控制释放载体的智能水凝胶,通常由于差的机械性能和慢的响应速度限制了它的实际应用。近年来,许多研究工作者围绕提高智能水凝胶的响应速度作出了大量的工作。综述了近年来提高智能水凝胶响应速度的研究进展。     

机械图样中应如何实施<技术制图 图线>新标准

本文表列了ＧＢ／Ｔ１７４５０ 与ＧＢ４４５７．４ 两个图线标准相应条文的比较,并就其主要差异作了阐述分析,同时指出了在机械图样中实施这两个标准时应注意的问题。     

Synthesis of Nanosized and Microporous Precipitated Hydroxyapatite in Synthetic Polymers and Biopolymers

In situ precipitation of microporous and nanosized hydroxyapatite particles (5–40 nm) has been conducted in poly(vinyl alcohol) and bovine serum albumin gels. The process, which is similar to biomineralization, is highly controlled with respect to microstructural features, such as size and shape, and to precipitation of hydroxyapatite phase having a calcium:phosphorus stoichiometric ratio of 1.67. Nanosized precipitated hydroxyapatite particles show remarkable thermal stability and do not decompose to other calcium phosphate phases, even at higher temperatures.     

Preparation and Proton Conductivity of Surfactant-Templated Mesoporous Silica Gels Impregnated with Protonic Acids

Surfactant-templated mesoporous silica gel that was impregnated with various protonic acids has been prepared, and we propose this material as a new type of proton conductor. The conductivity of the mesoporous silica gel that was impregnated with 5.0 M H₂SO₄ was ∼1 × 10⁻⁴ S/cm at room temperature in a dry nitrogen-gas atmosphere after drying in vacuo at room temperature; this value was four orders of magnitude greater than that of silica gel that was prepared via the conventional sol–gel method and impregnated with H₂SO₄. The amount of impregnated H₂SO₄ in the mesoporous silica gel was ∼2.5 times larger than that of impregnated H₂SO₄ in the conventional silica gel. The H₂O molecules in the mesoporous silica gel that was impregnated with H₂SO₄ remained in the pores of the gel, even after drying in vacuo at room temperature.     

Optical Spectra of Nickel-Bearing Silicate Gels Prepared by the Geopolymer Technique, with Special Reference to the Low-Temperature Formation of Liebenbergite (Ni2SiO4)

A nickel-bearing silicate gel was prepared from sodium disilicate and nickel nitrate solutions at room temperature. Then, the gel was heat-treated in air up to 800°C at intervals of 200°C. The products were completely amorphous after heating at ≤600°C. However, liebenbergite and cristobalite were identified as products of the crystallization of the gel after heating at 800°C. The polycondensation process of the gel was discussed based on X-ray diffractometry, thermogravimetry-differential thermal analysis, and optical spectroscopy, to clarify the easy crystallization of the gel to liebenbergite and cristobalite. The present technique is very useful for the low-temperature preparation of liebenbergite, which has potential application in the decomposition catalysis of chlorofluorocarbons, in connection with the problem with the ozone layer.     

Mullite Whiskers Grown from Erbia-Doped Aluminum Hydroxide–Silica Gel

Mullite whiskers and anisotropic grains that were derived from erbia-doped aluminum hydroxide–silica gel were studied. Firing 3.0-mol%-erbia-doped isostatically pressed pellets at 1600°C for 1.0–8.0 h resulted in a high surface concentration of mullite whiskers. Their c -axes were aligned preferentially along the pellet surface; the maximum length was 50 μm, and the maximum aspect ratio was 23. The pellet surface was fully covered by mullite whiskers, and small anisotropic grains with a low aspect ratio were observed in the bulk. The voids that were observed in the fracture surfaces were covered fully by mullite whiskers. The large number of voids resulted in an apparent density of 1.60 g/cm³ in the sintered pellets. The molar ratio of alumina to silica in the whiskers was in the range of 1.30–1.45 (an average value of 1.31), regardless of whether the alumina/silica powder compositions were mixed in a 3:2 or 2:1 ratio.     

香豆素小分子有机凝胶剂的合成及其凝胶化能力的测3

本文合成了四种带有不同烷基链的香豆素衍生物(1a、1b、2a、2b).通过观察成凝胶情况发现,带有三个烷基链的香豆素衍生物2能使有机溶剂凝胶化,而烷基链的长短对成其成凝胶的影响也是非常大的.与其它化合物相比,4d具有很好的凝胶化能力.能够通过加热冷却、超声处理等方法使多种溶剂凝胶化.由于香豆素化合物具有很强的荧光且具有...