Stacking trilayers to increase force generation

Multidirectional Artificial Muscles from Nylon

“…We measured normalized forces (Supporting Information) of up to 7.5 MPa (fully recoverable—no catch) (Figure F) and 55 MPa (with catch‐index of 0.12) (Figure B) from the bending actuators (Figure S7, Supporting Information). These measured forces are higher than the normalized peak force reported for an ionic‐liquid‐based bucky gel (231 kPa), conducting polymer bending actuators (0.4–0.9 MPa), and IPMC‐based bending artificial muscles (2–3 MPa) . The measured fully recoverable force is comparable to the normalized blocking force of 6.8 MPa generated by short piezo bimorphs (i.e., <10 mm), but the full dynamic range of these piezo bimorphs is only 400 µm (0.04 normalized to the length) at zero tip load …”

“…For example, although shape memory alloys can provide high contractile stress (200–480 MPa), their poor cycle life (<1000 cycles) at high tensile strains, high cost (300 $ kg −1 ), low efficiency, and difficult controllability limit their applications. Conducting polymers offer contractile stresses of 2–120 MPa and require low excitation voltage (<4 V), but they are slow, suffer from low electrochemical coupling, and also scalability of their produced force in the current generation of small film actuators is on the order of few mN . The recently discovered miniature linear and torsional artificial muscles fabricated from carbon nanotube yarns and nanowire yarns offer long cycle life (>1 million cycles), but their manufacturing cost is not low enough for commercialization yet.…”

Actuation and blocking force of stacked nanocarbon polymer actuators

“…As previously mentioned, several authors reported that multilayer of thin actuators was used for developing actuator showing both large displacement and force [12][13][14][15][16][17]. They also reported the multilayer actuator model.…”

“…Therefore, there are trade-off relations between the thickness of the actuator film (electrode and electrolyte) and bending displacement, speed, and force. In several studies, stacking several thin actuators has been used as a method of solving this issue of trade-off relations [12][13][14][15][16][17]. (Figure 1(b)) In this case, the most important issue is that the insulation layer between actuator electrodes prevents the contraction/elongation of each electrode layer, which decreases the motion of the stacked actuator.…”