TO-mdiSPAs: Topology Optimization of multi-directional Soft Pneumatic Actuators

Swagatam Islam Sarkar; Prabhat Kumar

cs.ROSep 30, 2026

TO-mdiSPAs: Topology Optimization of multi-directional Soft Pneumatic Actuators

Authors: Swagatam Islam Sarkar, Prabhat Kumar

Organizations: Department of Mechanical and Aerospace Engineering Indian Institute of Technology Hyderabad Telangana-502284, India

Abstract

Soft pneumatic actuators (SPAs) are highly promising and have been extensively explored within the field of soft robotics. Under pneumatic pressure loads, an SPA undergoes bending deformation to perform specific tasks. A multi- or omni-directional SPA can bend and move in any direction within a 3D space, leveraging its multiple degrees of freedom to realize various mechanical functions. This work presents a systematic methodology using topology optimization (TO) to achieve an optimized design for a multi-directional SPAs. To ensure manufacturing robustness, a three-field TO formulation considering blueprint, dilated, and eroded designs is implemented. Additionally, Darcy's law, incorporating a drainage term, is used to model the design-dependent nature of the pneumatic loading. A min-max optimization problem is formulated based on the target output deformations of the SPA unit and solved using the Method of Moving Asymptotes. The optimization yields a high-performing, unconventional geometric design. Finally, numerical simulations demonstrate that the optimized SPA successfully achieves versatile multi-directional movements.

Figures & tables

Panel of Figure 1 — Fig. 1 : Cross section of a symmetric quarter of an arm with multiple chambers

Panel of Figure 2 — Fig. 2 : Design domain of one chamber (symmetric half)

Panel of Figure 3 — Fig. 3 : Optimized single SPA chamber with pressure load: (a) MATLAB-optimized output, (b) corresponding 2D CAD model, and (c) 3D CAD representation.

Fig. 4 : 3D Optimized SPA CAD model of an arm consisting of ten chambers in each of the four directions: front ( f ), back ( b ), left ( l ), right ( r ).

Fig. 5 : A representation of undeformed optimized SPA model to be used as a gripper.

Fig. 6 : Deformed SPAs as a gripper - equal pressures are in front and left channels, back channel, and front and right channels in arm 1, arm 2, and in arm 3, respectively (Case 1).

Fig. 7 : Deformed SPAs as a gripper - different pressures are in front and left channels, front and right channels, and back and right channels in arm 1, arm 2, and in arm 3, respectively (Case 2).

Input pressure (MPa)					Deformations (mm)
Arm	Channels				$u_{x}$	$u_{y}$	$u_{z}$
Arm	$C_{f}$	$C_{b}$	$C_{l}$	$C_{r}$	$u_{x}$	$u_{y}$	$u_{z}$
1	0.150	-	0.150	-	1.948	-15.667	15.658
2	-	0.150	-	-	0.994	15.820	0.004
3	0.150	-	-	0.150	1.948	-15.667	-15.658

TABLE I : Case 1: Input and output data

Input pressure (MPa)					Deformations (mm)
Arm	Channels				$u_{x}$	$u_{y}$	$u_{z}$
Arm	$C_{f}$	$C_{b}$	$C_{l}$	$C_{r}$	$u_{x}$	$u_{y}$	$u_{z}$
1	0.050	-	0.075	-	0.009	-3.114	5.212
2	0.100	-	-	0.150	1.131	-7.809	-15.751
3	-	0.080	-	0.011	0.031	5.676	-0.630

TABLE II : Case 2: Input and output data

Explore similar work

Topology-Optimized Pneumatic Soft Actuator: Design and Experimental Validation
May 19, 2026Sumit Mehta, Konstantinos PouliosSoft Pneumatic Actuators Topology Optimization
Department of Civil and Mechanical Engineering Technical University of Denmark, Denmark
Soft Pneumatic Grippers: Topology optimization, 3D-printing and Experimental validation
Nov 24, 2025Prabhat Kumar, Chandra Prakash, Josh Pinskier +2Topology Optimization Soft Pneumatic Actuators
Department Mechanical and Aerospace Engineering. India Institute of Technology Hyderbad, Telangana 502285, India · CSIRO Robotics, Pullenvale, QLD 4069, Australia · Faculty of Mechanical Engineering, Delft University of Technology, Mekelweg 2, Delft, 2628CD, Zuid-Holland, The Netherlands
Soft Pneumatic Actuators for Soft Robotics: A Motion-Based Review of Actuation Mechanisms and Performance Trade-offs
May 24, 2026Mohammed AbboodiSoft Pneumatic Actuators Soft Robotics

May 19, 2026, cs.ROJ/K move · Enter open · S save

Topology-Optimized Pneumatic Soft Actuator: Design and Experimental Validation

Sumit Mehta, Konstantinos Poulios

Department of Civil and Mechanical Engineering Technical University of Denmark, Denmark

Soft Pneumatic Actuators Topology Optimization

Open paper AskPDF arXiv

This paper demonstrates the computational design of soft elastomeric pneumatic actuators using nonlinear topology optimization. An existing density- and porohyperelasticity-based topology optimization framework was extended from 2D to 3D and used to generate two manufacturable actuator designs, which were then studied numerically and experimentally. For both designs, the objective was to maximize the bending response for a prescribed actuation pressure under two different allowable strain limits. A key advantage of the employed topology optimization framework is that it can consistently, during the optimization, account for the very large deformations induced upon pressurization. The two optimized 3D designs were fabricated using stereolithography and experimentally tested to validate their performance.

Abstract

Explore similar work

Topology-Optimized Pneumatic Soft Actuator: Design and Experimental Validation

Soft Pneumatic Grippers: Topology optimization, 3D-printing and Experimental validation

Soft Pneumatic Actuators for Soft Robotics: A Motion-Based Review of Actuation Mechanisms and Performance Trade-offs