1. Endoscopy is a medical procedure which allows the surgeon to view the interior of a
human body [1]. Endoscopy procedures also allow doctors to locate and remove foreign
objects from inside the body without having to make an incision. However, a traditional
endoscope is relatively rigid, inflexible, and large as compared to an average person’s
oesophagus, leading to tissue trauma and perforation when they are inserted and
navigated through soft tissues [2]. It is also very expensive.
These problems can be avoided with soft robotics, as soft robotics makes use of the
‘mechanical intelligence’ of soft materials [2]. An example of soft materials is a silicon-
based elastomeric material known as EcoflexTM. EcoflexTM is low cost, easy to work
with and readily available in the market. Most importantly, it is able to withstand
bending and stretch up to 9 times its original length [3], making it less rigid as compared
to hard robots, resulting in less tissue trauma and perforation.
This project aims to create a low-cost endoscopic grasper that would be able to
overcome some of the problems posed by a traditional endoscope. Thus, a soft
endoscopic robot of 2 cm in diameter, equipped with a 4-armed gripper and USB
camera, was designed and would be powered by a pneumatic actuator.
INTRODUCTION
METHODS
A Novel Soft Robotics Approach towards the
Development of a Low-Cost Endoscopic Grasper
for Delicate Navigable Manipulation of Soft Tissues
Michelle Livia Adiwangsa, Lou Wei Hao Darren, Foo Shao Kai
Research mentor: Prof. Raye Yeow Chen Hua
Teacher mentors: Ms Lim Wei Li & Ms Lim Hui Ling Jacqueline
RESULTS AND DISCUSSIONS
Overall Strength and Flexibility of Endoscope
As seen in Figure 7, structural integrity of the endoscopic body
was decreased due to the presence of air bubbles. In addition, it
also reduced the maximum deflection angle of the endoscopic
body, decreasing its maneuverability. To eradicate this problem,
degassing was carried out during the fabrication of the soft robot
to remove the air bubbles.
Lens System of Endoscope
One of the problems encountered was the inability of the endoscopic body to bend when actuated. Insertion
of the lens system into the soft endoscopic body hinders the movement and flexibility of the soft robot. This
is due to the stiffer external camera casing. To resolve this, an external lens system that made use of Ai-
ballTM was adopted instead. Thus, with an external lens system, the stiffness of the endoscopic robot would
not be changed, allowing it to retain its bending capabilities.
X-Shaped Gripper
In theory, by placing a piece of paper dipped in
EcoflexTM on the side of the gripper where the air
channels are exposed, the gripper would be able to
bend. However, through experimentation, our gripper
failed to bend upon actuation. This could have been
caused by the uneven surface of the paper, obstructing
the tiny air channels (1 mm diameter). Pneumatic
actuation was therefore found to be unsuitable for
bending of the gripper. Figure 9 shows the initial
prototype of the proposed soft endoscopic grasper.
Tendon-pulley mechanism was
used in place of the pneumatic
actuation, with the design of the
gripper redesigned to better fit
the new mechanism. It works
based on the concept of
moments, which allowed the
arms to successfully bend
downwards with an upward force.
Tendon Pulley Mechanism Pneumatic Actuation
Force provided is uni-directional Force provided is non-directional
Efficient transfer of force
Inconsistency in direction of force results in
inefficient transfer of applied force
Easier to control arms of gripper
Arms of gripper might not actuate fully due to non-
directional forces, making it harder to control
Even so, the new design of the
soft robot rendered the endoscopic
body to be unable to bend, due to
the larger mass and thus inertia of
the soft robot’s lower half as seen
in Figure 10 and 11.
Figure 9: Initial prototype of soft endoscopic grasper
Table 1: Comparison between tendon pulley mechanism and pneumatic actuation
FUTURE WORK
Future work could focus on using a more suitable camera that is more flexible and smaller in size. The
method to which the gripper is sealed can also be improved. Once a soft endoscopic grasper has been
successfully made, tests can be carried out by using animal tissues of different mass to determine its
strength and durability. Lastly, experiments need to be carried out to determine whether the soft robot can
still work at its maximum potential inside a real human body, and show whether the future soft endoscopic
grasper would be ready to replace the traditional endoscope for endoscopy procedures.
CONCLUSION
A prototype of a low-cost endoscopic grasper was successfully created. The method of using pneumatic
actuation was replaced with tendon-pulley mechanism due to the problems arising. The fingers of the
grippers were successfully bent using the tendon-pulley mechanism, thus proving that it is a feasible
mechanism that can be used to bend the gripper’s fingers in future prototypes. However, due to the larger
mass and thus inertia of the endoscopic grasper’s lower half, the entire endoscopic grasper was unable to
bend. Thus, future work has to be carried out to improve the soft endoscopic grasper.
REFERENCES
[1] American Cancer Society (2012, October 12). Endoscopy. Retrieved on 13 December 2013, from http://www.cancer.org/acs/groups/cid/documents/ webcontent /003174-pdf.pdf
[2] Sangbae Kim – Massachusetts Institute of Technology, Cambridge, MA, USA; Cecilia Laschi – The BioRobotics Institute, Scuola Superiore Sant’Anna, Pisa, Italy; Barry Trimmer – Tufts University, Medford, MA, USA. “Soft robotics: a
bioinspired evolution in robotics”
[3] Ecoflex (n.d). Ecolex® Series: Super-soft, Addition Cure Silicone Rubbers. Retrieved on 12 December 2013, from http://www.smooth-on.com/tb/files/ECOFLEX_SERIES_TB.pdf
[4] Shapiro, Y., Wolf, A., & Gabor, K. (2011). Bi-bellows: Pneumatic bending actuator. Sensors and Actuators A: Physical, 167(2), 484-494. doi:10.1016/j.sna.2011.03.008
[5] Ilievski, F., Mazzeo, A. D., Shepherd, R. F., Chen, X., & Whitesides, G. M. (2011). Soft Robotics for Chemists. Angewandte Chemie International Edition, 50(8), 1890-1895. doi:10.1002/anie.201006464
[6] De Greef, A., Lambert, P., & Delchambre, A. (2009). Towards flexible medical instruments: Review of flexible fluidic actuators. Precision Engineering, 33(4), 311-321. doi:10.1016/j.precisioneng.2008.10.004
Assemble all parts (Fig 3) together.
Then, insert the 4 titanium rods to create the 4 air chambers (Fig 4).
Prepare the EcoflexTM mixture.
Using an electronic beam balance, pour 15 grams each of part A and part B of
EcoflexTM. Next, use a centrifugal vacuum mixer to mix this mixture. Set the
speed at 2000 rpm for 30 seconds, then 2500 rpm for another 30 seconds. This is
to ensure simultaneous mixing and de-aeration of EcoflexTM.
Fabrication of endoscopic body
Pour EcoflexTM mixture into the assembled mould slowly to avoid air bubbles. After
pouring the mixture inside the mould, heat the mould at 59 °C until it hardens and
dries up. Dissemble the mould and take out the soft endoscopic body.
2. Fabricate the endoscopic body
3. Fabricate the gripper and combine it with the endoscopic body
Repeat the steps above. Next, cover the gripper with paper to seal the air
chambers (Fig 5). Then, assemble the endoscopic body and gripper together.
Lastly, use a syringe to inject air and power the soft robot (Fig 6).
Figure 4: Air chambers for the soft endoscopic body
Figure 7: Holes created by bursting of air bubbles
holes
*ALL IMAGES AND PHTOGRAPHS WERE SELF TAKEN AND DRAWN
Small
angle
of
Upper
Half
Lower
Half
Endoscopic
body
Arms of
gripper
Figure 10: Components of the soft robot Figure 11: Endoscopic body being
injected with air
deflection
1. Design the mould
A computer software
SolidworksTM was used to
design the robot’s mould
before it was sent for 3-
dimensional (3D) printing.
The mould was separated
into parts (Figures 1 - 2) for
easy dissembling after the
fabrication process.
Figure 2: SolidworksTM mould for gripper (3D view)
Figure 1: SolidworksTM mould for upper part (left) and lower part
(middle) of the endoscope, and camera support (right)
Figure 3: Parts of mould before assembling
Figure 5: Sealing the gripper with paper Figure 6: Soft endoscopic robot bending upwards after injecting
air into one of the air chambers
Tendon-Pulley Mechanism