Person:

Martinez, R

The development of soft pneumatic actuators based on composites consisting of elastomers with embedded sheet or fiber structures (e.g., paper or fabric) that are flexible but not extensible is described. On pneumatic inflation, these actuators move anisotropically, based on the motions accessible by their composite structures. They are inexpensive, simple to fabricate, light in weight, and easy to actuate. This class of structure is versatile: the same principles of design lead to actuators that respond to pressurization with a wide range of motions (bending, extension, contraction, twisting, and others). Paper, when used to introduce anisotropy into elastomers, can be readily folded into 3D structures following the principles of origami; these folded structures increase the stiffness and anisotropy of the elastomeric actuators, while being light in weight. These soft actuators can manipulate objects with moderate performance; for example, they can lift loads up to 120 times their weight. They can also be combined with other components, for example, electrical components, to increase their functionality.

The fabrication and properties of “fluoroalkylated paper” (“(R^F) paper”) by vapor-phase silanization of paper with fluoroalkyl trichlorosilanes is reported. (R^F) paper is both hydrophobic and oleophobic: it repels water ((θ_{app}^{H2O} > 140^{\circ})), organic liquids with surface tensions as low as (28 \space mN \space m^{-1}), aqueous solutions containing ionic and non-ionic surfactants, and complex liquids such as blood (which contains salts, surfactants, and biological material such as cells, proteins, and lipids). The propensity of the paper to resist wetting by liquids with a wide range of surface tensions correlates with the length and degree of fluorination of the organosilane (with a few exceptions in the case of methyl trichlorosilane-treated paper), and with the roughness of the paper. (R^F) paper maintains the high permeability to gases and mechanical flexibility of the untreated paper, and can be folded into functional shapes (e.g., microtiter plates and liquid-filled gas sensors). When impregnated with a perfluorinated oil, (R^F) paper forms a “slippery” surface (paper slippery liquid-infused porous surface, or “paper SLIPS“) capable of repelling liquids with surface tensions as low as (15 \space mN \space m^{-1}). The foldability of the paper SLIPS allows the fabrication of channels and flow switches to guide the transport of liquid droplets.