Page 243 - Flexible Robotics in Medicine

232 Chapter 10

robots utilizing soft materials such as elastomers, which are light and inexpensive, with the
capability to change shape under stimuli due to its soft structure.

In several applications where hard robots are used, the focus was on the fabricating
mechanical joints [1]. The core contribution is the fabrication of joints in a one-step process
(stereolithography method) without the need for assembly. Several experiments were
carried out to obtain the optimum dimensions for the distinctive features, such as part size
and clearance, and ways of support generation for the stereolithography method. Due to the
accuracy level of the machine, layer thickness, and the resolution in the planar details, the
smoothness for rounded parts resulted in the staircase effect.
A trial-and-error simulation approach was designed where electromechanical systems are
implemented to determine the degrees of motion of necessary materials such as bars and actuators
[2]. Bars are connected to each other to form trusses, and their structural behavior is modified by
changing the number and the arrangement of bars. Linear actuators were used to actuate and test
the motions of these bars. The most qualified configurations are then fabricated using three-
dimensional printing technology, and the working mechanism is tested in real-time. This approach
resulted in the maximization of architectural flexibility and the possibility of obtaining diverse
types of motions due to different configurations. Some of the critical configurations displayed
motions such as bipedalism, crawling motion, and crab-like sideways movement.

Biomimetic robots take design inspiration from biology and nature. These robots are
fabricated using shape deposition manufacturing (SDM), where mechanisms are
simultaneously fabricated and assembled [3,4]. SDM can be used to fabricate a sprawled
hexahedral self-stabilizing posture with six legs. The polygon structure supports its center
of mass, and the structure is actuated by pneumatic pistons. Due to the advantages of
metallic parts in specific applications, rapid prototyping of metal parts [5] could be utilized.

Soft robots make use of the motion capabilities of its soft continuum bodies made of
elastomeric materials [6] to achieve three-dimensional motions [7]. The soft continuum bodies
were made of silicone (Ecoflex) along with Polydimethylsiloxane (PDMS) by casting using
3D-printed polymers. PDMS is harder than Ecoflex and has a limited range of deformation [8],
contributing to control of the bending of the robot. Pneumatic actuation is utilized, and the
difference in the stiffness of the two materials created an intriguing material structure, which
made the varying actuation possible [9]. Further functional possibilities were demonstrated with
the incorporation of functional components. However, the tether embedded in the tentacles for
pneumatic actuation limits the tentacles to be reduced beyond the centimeter scale.

Soft robots have certain advantages over conventional hard robots such as locomotion in
irregular terrain, handling fragile and inconsequential objects, such as fruits to human
organs, which are difficult for hard robots to handle [10]. Elastomeric materials can be used
as soft grippers by actuating with pneumatic systems [6], microfluidic networks [11], and
also shape memory alloy (SMA) [12]. Nematic liquid crystals [13] embedded into