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Sakriya Thapa - May 2019

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RESEARCH REPORT
DEPARTMENT OF MECHANICAL ENGINEERING
May, 2019
Research Subject: Making of low costing 3D-printed personalized prosthetic hands for
children with amniotic band syndrome (including simulating sensors).
Prepared by: Sakriya Thapa (Student ID: 201850000042 – Mechanical Engineering)
Statement of purpose: A case study using 3D-printed conformal electrode arrays to
sense the pressure distribution on human-machine interface and to build a 3D printed
prosthetic to aid children suffering from amniotic band syndrome.
Abstract:
Interfacing anatomically conformal electronic components, such as sensors, with biology
is central to the creation of next-generation wearable systems for health care and human
augmentation applications. Thus, there is a need to establish computer-aided design and
manufacturing methods for producing personalized anatomically conformal systems,
such as wearable devices and human-machine interfaces (HMIs). Here, we show that a
three-dimensional (3D) scanning and 3D printing process enabled the design and
fabrication of a sensor-integrated anatomical human-machine interface (AHMI) in the
form of personalized prosthetic hands that contain anatomically conformal electrode
arrays for children affected by amniotic band syndrome, a common birth defect. Here the
children have their limb or any body parts strained or entangled by birth. Thus, we would
look the possibilities of creating personalized 3D printed prosthetics for children who are
bearing the syndrome or disease and try to help them move their limbs or body parts to
function as desired.
Introduction:
Additive manufacturing, also commonly named as 3D printing, has emerged as a valuable
fabrication process for creating personalized and anatomical biomedical devices by
inheriting medical imaging data (data collected from the medical imaging sonar, UV or Xrays devise) with computer-aided design (CAD) tools. Till now many applications has
been benefitted by the ease and flexible nature of additive manufacturing in the noble
field of medical science. Whose examples we can see around us also in which disabled
people or those who were having some kind of defects in their body parts have been
replaced with modern 3D printed prosthetics and living a much better life. In my research
period I happened to read about engineers and scientists trying to use human tissues or
equivalent materials as 3D printing base material to imitate and create prosthetics which
is highly and easily compatible to human body. This is a kind of tissue regeneration
process in unnatural or man-made way. In addition to tissue regeneration applications,
3D printing has been used to fabricate patient-specific anatomical models for surgical
testing applications
Mode of use and procedure:
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At first the medical imaging data of the deformed limbs or body part of a child or
casualty is taken for 3D printing which is often collected via magnetic resonance
imaging (MRI) and computed tomography (CT) scanning.
Not only the medical imaging devices but 3D scanning techniques also have been
used due to the relatively low cost, portability, flexibility in range and resolution.
Also, 3D scanning technique is lot user friendly compared to medical imaging. Most
common 3D scanning method used in medical field is laser 3D scanning.
The defected limb is replicated using Alija-Safe 300Q resin and the polyurethane
replica of the limb was scanned using a single camera, single projector structuredlight 3D scanning system.
The limb replica is then manually rotated after each scan by an angle Δθ using a
turntable. The output from each 3D scanning measurement was a point cloud P,
which is after referred to as a scan.
The limb replica is hence scanned from 0–360° by using a constant rotational angle
step size (Δθ). Where, Δθ ranges from 5°—θmax. Here, θmax is considered the
maximum rotational angle at which the two scans could be successfully registered
using the vendor-provided auto-alignment algorithm.
The digital models for the components associated with a non-personalized
prosthetic hand for amniotic band syndrome defects (Raptor Hand; e-NABLE) are
first downloaded from an online database. This data contains many moveable and
non-moveable parts imitating the actual human limb.
The next step is to create a 3D model of the prosthetic or the replicated limb using
any of the online CAD software available.
Also, the stimulation and analysis of the part to be printed is needed to be studied
prior to printing the actual physical limb.
The prosthetics are printed using multiple commercially-available polymer
extrusion 3D printers (either a Prusa i3 MK2 from Prusa Research or a Mini 2 from
Lulzbot). Parts were printed with a 0.18 mm layer height, 10% infill density (for
support structures), and speed of 30 mm/s for wall printing and 40 mm/s for infill
printing.
But before placing the prosthetic limb, the dorsal side of the participant’s hand is
wrapped in a flexible thin film of plastic covered with copper tape to reduce the
potential effects of skin moisture get trapped on the sensor signal.
Then after, the straps on the prosthetic hand are adjusted to fit the participant. The
participant now needs to place the prosthetic hand on a rigid flat table with the
palmar side facing upward and the wrist relaxed in a straight position, referred to
as the ‘relaxed’ position.
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The response of each sensor (1–5) is then measured by recording the resistance
across each electrode pair.
The participant again needs to flex their wrist, which creates a grasping and flexing
action in the prosthetic hand, while the response from each pressure sensor in the
array was recorded using the aforementioned procedure.
Summarizing:
With the continued development of 3D printing technology and materials, 3D printers are
becoming increasingly affordable and inexpensive, with printers capable of fabricating
prosthetic hands available in the range of $300 to $1,500. As our motto is to make low
cost prosthetics which is more affordable and widely ranged.
Polymer extrusion 3D printers are among the most inexpensive systems in nowadays
scenario. The polymer extrusion 3D printers continuously extrude the preprocessed
thermoplastic filaments through a heated nozzle leading to layer-by-layer deposition of
the polymer in a tool path that is generated from a corresponding digital model of the 3D
printed part.
As I read more articles on the low-cost 3D printing of the prosthetics, I realized previous
researches has shown that most patients indicate the aesthetic appearance of an
amputated finger plays a more important role than function. Thus, the ability to rapidly
prototype bio-inspired prosthetic hands of various mechanical design and material color
makes 3D printing a promising approach for fabrication of low-cost prostheses for
children.
New Research Idea:
Having an affordable or low cost 3D printing technique the components of the nonpersonalized and personalized prosthetic hands, we can generate more and more
prosthetics to highly needed casualties or children in this cases to be able to use their
custom built prosthetic limbs to make movements or do daily casual works like walking,
using hands to do works.
Also, I came to read the articles about these types of prosthetics, in future we can be able
to use human tissue like materials in order to simulate the natural feel while using the
prosthetics despite of the discomfort and sweating by using the prosthetics for a longer
period of time. As the human tissue like materials are in process to be used as the 3D
printing material which would be highly beneficial and feasible too.
While if the movements and pressure sensitivity of the entangled or not functional limbs
can be studied more precisely by using both 3D scanning and medical imaging devices
so that we can build prosthetics that can simulate the movements of the natural limbs and
give the children or user more natural feeling movements and ease of using their
prosthetics instead of just the bulky accessory like thing attached to their body.
In future I would like to deep study more articles and journals about this topic in order to
be able to gain more knowledge about highly affordable and easy and quickly able to
build prosthetics for greater use.
References:
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Low-cost sensor-integrated 3D-printed personalized prosthetic hands for children
with amniotic band syndrome
(Murphy SV, Atala A. 3D bioprinting of tissues and organs. Nat Biotech. 2014;32(8):773–
85.
Gough NR. Bioprinting Cartilage Scaffolds. Science Signaling.)
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