Fully-printable soft actuator with variable stiffness by phase transition and hydraulic regulations

TY - JOUR

T1 - Fully-printable soft actuator with variable stiffness by phase transition and hydraulic regulations

AU - Liao, Tingchen

AU - Kalairaj, Manivannan Sivaperuman

AU - Cai, Catherine Jiayi

AU - Tse, Zion Tsz Ho

AU - Ren, Hongliang

N1 - Funding Information: Funding: This work was supported by the Shun Hing Institute of Advanced Engineering (SHIAE project BME-p1-21, 8115064) at the Chinese University of Hong Kong (CUHK), CUHK Direct Grant for Research 4055139, and the Singapore Academic Research Fund under Grant R-397-000-353-114. Publisher Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

PY - 2021/10/14

Y1 - 2021/10/14

N2 - Actuators with variable stiffness have vast potential in the field of compliant robotics. Morphological shape changes in the actuators are possible, while they retain their structural strength. They can shift between a rigid load-carrying state and a soft flexible state in a short transition period. This work presents a hydraulically actuated soft actuator fabricated by a fully 3D printing of shape memory polymer (SMP). The actuator shows a stiffness of 519 mN/mm at 20◦ C and 45 mN/mm at 50◦ C at the same pressure (0.2 MPa). This actuator demonstrates a high stiffness variation of 474 mN/mm (10 times the baseline stiffness) for a temperature change of 30◦ C and a large variation (≈1150%) in average stiffness. A combined variation of both temperature (20–50◦ C) and pressure (0–0.2 MPa) displays a stiffness variation of 501 mN/mm. The pressure variation (0–0.2 MPa) in the actuator also shows a large variation in the output force (1.46 N) at 50◦ C compared to the output force variation (0.16 N) at 20◦ C. The pressure variation is further utilized for bending the actuator. Varying the pressure (0–0.2 MPa) at 20◦ C displayed no bending in the actuator. In contrast, the same variation of pressure at 50◦ C displayed a bending angle of 80◦ . A combined variation of both temperature (20–50◦ C) and pressure (0–0.2 MPa) shows the ability to bend 80◦ . At the same time, an additional weight (300 g) suspended to the actuator could increase its bending capability to 160◦ . We demonstrated a soft robotic gripper varying its stiffness to carry various objects.

AB - Actuators with variable stiffness have vast potential in the field of compliant robotics. Morphological shape changes in the actuators are possible, while they retain their structural strength. They can shift between a rigid load-carrying state and a soft flexible state in a short transition period. This work presents a hydraulically actuated soft actuator fabricated by a fully 3D printing of shape memory polymer (SMP). The actuator shows a stiffness of 519 mN/mm at 20◦ C and 45 mN/mm at 50◦ C at the same pressure (0.2 MPa). This actuator demonstrates a high stiffness variation of 474 mN/mm (10 times the baseline stiffness) for a temperature change of 30◦ C and a large variation (≈1150%) in average stiffness. A combined variation of both temperature (20–50◦ C) and pressure (0–0.2 MPa) displays a stiffness variation of 501 mN/mm. The pressure variation (0–0.2 MPa) in the actuator also shows a large variation in the output force (1.46 N) at 50◦ C compared to the output force variation (0.16 N) at 20◦ C. The pressure variation is further utilized for bending the actuator. Varying the pressure (0–0.2 MPa) at 20◦ C displayed no bending in the actuator. In contrast, the same variation of pressure at 50◦ C displayed a bending angle of 80◦ . A combined variation of both temperature (20–50◦ C) and pressure (0–0.2 MPa) shows the ability to bend 80◦ . At the same time, an additional weight (300 g) suspended to the actuator could increase its bending capability to 160◦ . We demonstrated a soft robotic gripper varying its stiffness to carry various objects.

KW - Hydraulic actuators

KW - Shape memory polymers

KW - Soft actuators

KW - Soft gripper

KW - Valves

KW - Variable stiffness

UR - http://www.scopus.com/inward/record.url?scp=85118320963&partnerID=8YFLogxK

U2 - 10.3390/act10100269

DO - 10.3390/act10100269

M3 - Article

AN - SCOPUS:85118320963

SN - 2076-0825

VL - 10

JO - Actuators

JF - Actuators

IS - 10

M1 - 269

ER -