The Use of Photocycloaddition Reactions to Drive Mechanical Motions Resembling Humanoid Movements.

With the aim of producing a photomechanical material for incorporation in soft microrobots, a one-dimensional diene coordination polymer (CP) [Cd(F-bpeb)(3-CBA)2]n (CP1, F-bpeb=4,4'-((1E,1'E)-(2,5-difluoro-1,4-phenylene)bis(ethene-2,1-diyl))dipyridine, 3-HCBA=3-chlorobenzoic acid) was synthesized and characterized. Irradiation of CP1 with ultraviolet (UV) or visible light causes [2+2] photocycloaddition reactions resulting in the introduction of crystal strain which triggers various types of crystal movements. Composite films of CP1-PVA (SC) fabricated by dispersing CP1 crystals into polyvinyl alcohol (PVA) solution allow amplification of the crystal movement so that the film strips exhibit fast and flexible curling upon photoirradiation. The composite films may be cut into long rectangular strips and folded to simulate soft microrobots which exhibit a variety of fast, flexible and continuous photomechanical movements resembling a human performing various gymnastic exercises.

Shaping Soft Robotic Microactuators by Wire Electrical Discharge Grinding.

Inflatable soft microactuators typically consist of an elastic material with an internal void that can be inflated to generate a deformation. A crucial feature of these actuators is the shape of ther inflatable void as it determines the bending motion. Due to fabrication limitations, low complex void geometries are the de facto standard, severely restricting attainable motions. This paper introduces wire electrical discharge grinding (WEDG) for shaping the inflatable void, increasing their complexity. This approach enables the creation of new deformation patterns and functionalities. The WEDG process is used to create various moulds to cast rubber microactuators. These microactuators are fabricated through a bonding-free micromoulding process, which is highly sensitive to the accuracy of the mould. The mould cavity (outside of the actuator) is defined by micromilling, whereas the mould insert (inner cavity of the actuator) is defined by WEDG. The deformation patterns are evaluated with a multi-segment linear bending model. The produced microactuators are also characterised and compared with respect to the morphology of the inner cavity. All microactuators have a cylindrical shape with a length of 8 mm and a diameter of 0.8 mm. Actuation tests at a maximum pressure of 50 kPa indicate that complex deformation patterns such as curling, differential bending or multi-points bending can be achieved.