Soft robotic manipulators with fluidic actuation are devices with easily deformable structures that
comprise a set of chambers that can be pressurized to achieve structural deflection. These devices
have experienced a rapid development in recent years, which is not least due to the advantages
they offer in terms of robustness, affordability, and compliance. Nowadays, however, soft robotic
manipulators are designed mostly by intuition, which complicates design improvement and
hampers the advancement of the field. In this paper, a general study of the the design of soft
robotic manipulators with fluidic actuation is presented, using an analytical derivation. The study
relies on a novel approach that is applicable to a general design, and thus provides a common
framework for the design of soft robots. In the study, two design layouts of interest are first justified,
which correspond to extending and contracting devices. Design principles for each of the layouts
are subsequently derived, both for planar and 3D scenarios, and considering operation to support
any external loading and to provide any desired deflection. These principles are found to agree
with the main design trends in literature, although they also highlight the potential for improvement
in specific aspects of the design geometry and stiffness distribution. The principles are used to
identify the most suitable design for both extending and contracting devices in 2D and 3D, and
extract insight into their behavior.. To showcase the use of these design principles, a prototypical
scenario in minimally invasive surgery requiring a manipulator segment capable of bending in any
direction is defined, where the objective is to maximize its lateral force. The principles are applied
to determine the most suitable design. These also highlight the need for numerical analysis to
optimize two design parameters. Finite element simulations are developed, and their results are
reported. Among the most relevant are the fact that the cross-sectional area with pressurized fluid
should be maximized, and that the stiffness in the design should be selected to minimize structural
stretching. The simulations yield the optimal design, which offers higher force than existing,
reference ones. The simulations also provide verification for the study.