The development of 3D soft-robotic components is currently hindered by material limitations associated with conventional 3D printing techniques. To overcome this challenge, we propose an indirect 3D printing approach based on the fabrication of 3D printed sacrificial templates.High-resolution micromolds produced by direct laser writing were infused with polymers and then dissolved, leading to the final 3D printed soft microstructures. We used this method to indirectly print 3D and 4D soft-microrobots. The versatility of our technique is shown through the fabrication and actuation of gelatin helices filled with magnetic nanoparticles. In addition, we show that stent-like microstructures with shape memory properties can be manufactured with minimum features of 5 µm, which is 40 times smaller than those reported to date. In summary, the utilization of this technique can overcome obstacles associated with the fabrication of soft microrobots and surgical tools for minimally invasive surgery.

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Polypropylene (PP)-based composites containing 20 wt.% wool fibres were successfully prepared using a simple melt blending procedure. A blend of a commercial-grade PP and a maleinised PP was chosen as the matrix. To investigate the effects of modifying the fibre surface on the fibre/matrix adhesion, wool fibres were used as received, oxidised, or functionalised with a silane-based coupling agent, capable in principle of reacting with both the fibres and the polyolefinic matrix. The silanisation of the fibres and the consequent surface modifications were assessed using infrared spectroscopy and scanning electron microscopy. The resulting PP-based composites were thoroughly characterised in terms of their morphology, thermal stability and mechanical behaviour

The yield behavior of commercial homopolymer polypropylene modified by elastomeric metallocene-catalyzed polyolefin blends was investigated by carrying out uniaxial tension, uniaxial compression, plane strain compression, and simple shear mechanical tests. Investigation was performed using specimens machined from isotropic compression molded plates. The onset of yielding was determined by means of the residual strain method. Experimental data was fitted according to the two most popular yield criteria in the polymer field-modified Tresca and modified Von Mises criteria. Both criteria provided reasonable predictions of the yield onset locus despite the tendency of polymers to develop crazes under positive hydrostatic pressure. A generalized yield locus based on the modified Von Mises criterion and the Lazzeri and Bucknall relationship was constructed for PP/POE blends. In addition, for one blend composition the effect of the polypropylene matrix crystalline morphology-altered by thermal annealing-was investigated.

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