Stiffness variation is useful in soft robots, especially for continuum manipulators which have a high slenderness ratio. Softness intrinsically gives robots high flexibility of movement, but stiffness gives the robots enough carrying capacity. Many types of continuum manipulators can change their stiffness; however, the both large-range and fast-response stiffness variation has not been realized. In this work, an omnidirectional steering flexible manipulator with large-range and fast-response stiffness variation was designed and fabricated. It was composed of a nested structure with a stiffness variation layer, a tendon-driven layer, and a transport channel. The stiffness variation was achieved by the phase transition of LMPA (Low-Melting Point Alloy) with a melting point of 50°C. Heating and cooling to the LMPA were performed by a tubular spring-like copper tube embedding in the LMPA. The tube not only acts as a skeleton of the manipulator, but also the material and structure of it bring the fast heat exchange. The motion of the manipulator was driven by tendons going through the holes of a threaded spring-like elastic skeleton which is flexible still can appropriately balance the self-weight of the manipulator. Continuum manipulators with one and two omnidirectional segments were fabricated to show the performance of movement and stiffness variation. Each segment is of 15 cm length and with diameter of 21 mm. The test shows that the stiffness of the manipulator has a factor of 45 variations in 15 seconds, and the stiffness variation is adequate to complete some challenging tasks like screw tightening and loosing.

In this work, a cross-linked porous polyimide (PI) network, fabricated from an “elongated” dianhydride and melamine, was synthesized by polycondensation and thermal dehydration. The as-prepared PI revealed an excellent adsorption performance and removal for acid orange 10 (AO-10) from aqueous solution. The adsorption quantity can reach 599 mg/g when the initial concentration is 500 mg/L with the temperature 298 K and pH value of 3. The maximum desorption ratio can be 38.9%. It is expected that the adsorption quantity and desorption ratio can be optimally improved by changing the length of PI monomer, indicating the cross-linked porous PI network is not only served effectively in sewage treatment but also recycled. Pseudo-2nd-order kinetic model and Langmuir isotherm are better fitted with the kinetic data and the adsorption equilibrium data respectively.

Ordered porous polyimide films were fabricated from (AB)_m type of diblock copolymer polyimide-b-polystyrene (PI-b-PS). An increase in PS volume fraction (f ^V_PS) is beneficial to decrease the relative dielectric constants and water contact angles of the obtained porous PI films: the relative dielectric constant decreases to 1.89 and water contact angle decreases to 43° when f ^V_PS is 0.36, indicating porous PI films can be used as low-κ material and have good wettability. The solvent uptake of the porous PI films increases with increasing f ^V_PS. A net-like morphology appears when f ^V_PS reaches 0.36. The net-like porous PI film reaches equilibrium uptake of water within approximately 2.5 h, with a final equilibrium uptake ratio of 17.5%, and reaches equilibrium uptake of toluene within approximately 8 h, with a final equilibrium uptake ratio of 15.4%, displaying the highest and fastest solvent uptake compared with other microstructured porous PI films, which is ascribed to the specific characteristic of the interconnecting porous channels derived from the self-assembly of PI-b-PS with f ^V_PS 0.36. Introducing thermally degradable segments to PI-based block copolymer is an effective method to prepare porous PI films and can enhance some of their properties.

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