Assessment of Soft
Artificial Skin with
Pressure Sensibility
Team Collaboration
James Courtney
Energy Engineering
Technology
Ashley Galvan
ET 493: Senior Design I
Instructor: Dr. Cris Koutsougeras
Advisor: Dr. Mohammad Saadeh
Spring 2015
3/27/2015
Computer Engineering
Technology
Hunter LaFleur
Energy Engineering
Technology
Table of Contents
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Abstract
2
Purpose
3
Theory
4
Materials
5
Design
6
Progress
7
Deliverables
8
Works Cited
9
ET 493: Senior Design I |Southeastern Louisiana University
1
Abstract
The aim of this senior project is to commence a study for evaluating soft artificial skin-like
material with pressure sensibility. The sensor used to measure and detect pressure is a force
sensing resistor (FSR). The project proposes to apply an array of FSRs that can be embedded
underneath a layer of platinum silicone. The sensors will be appropriately spaced to provide a
sensing map for the model platform. The array of sensors will identify any external force acting
on the surface by different locations. The application of that force will allow the location of that
applied force to be identified.
The skin-like platform will be tested on a materialization system. It will be animated using
signals of know amplitudes and frequencies. It will allow measuring and recording the properties
of the surface, such as its viscoelasticity. This data will be compared to FSR readings and modify
the force-sensation relation.
The figure above illustrates a simple FSR sensor. It is a sensor that uses polymer film, which
triumphs over traditional force sensing devices. These sensors have a wide measurable force
range but most important factor is the space these devices occupy is minimal and beneficial to
the system they will be applied to.
ET 493: Senior Design I |Southeastern Louisiana University
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Purpose
The purpose of this project is to receive tactile sensory feedback from external inputs applied to
the artificial skin-like surface. This growing study can be applied to robotic arms, which can
gather information and respond to given external inputs. The feedback improves control for
robotic arms. Recent studies of sensory feedback allow the user to improve control of those
devices. The ideal application of this system will be implanting the sensibility function to
prosthetic limbs for any individual with amputated limbs. This system will give responsive
feedback of the prosthetic and improve the quality of life of any individual that can feel that
response.
ET 493: Senior Design I |Southeastern Louisiana University
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Theory
Force-sensing resistors (FSR) were invited in 1977 by Franklin Eventoff. He later founded
Interlink Electronics, a company based on his invention. FSRs consist of a conductive polymer.
This polymer changes resistances as an application of force is introduced to its surface. The
sensor is supplied with polymer sheet or ink that is applied by screen printing. The sensing film
consists of both electrically conducting and non-conducting particles suspended in matrix. FSRs
function as an open circuit at no load. Once pressure is applied, the resistance of the FSR drops.
This drop is utilized to measure the force applied. FSRs are passive resistors and configured in
voltage divider circuits. They allow for a simple conversion of resistance-to-voltage.
The equation above is the output from a FSR device. The output voltage increases with
increasing force. The figure below will show response due to an external force.
ET 493: Senior Design I |Southeastern Louisiana University
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Materials
Dragon Skin 10 Med
Dragon Skin 10 MED is a high performance platinum cure silicone rubber that is very soft,
strong and stretchy. For application, the material can stretch without tearing or distorting. It will
return to its original form. This specific type of silicone is suitable for applications with
repetitive motion and animatronics. The solution can be mixed from by weight or volume 1A:1B
and cures at room temperature.
Vacuum Chamber Kit
This kit includes a 3 CFM single stage vacuum pump rated to 50 microns
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3 Gallon High Strength 304 SS Chamber
3/4” Thick Clear Acrylic Lid
Custom Industrial Grade Silicone Gasket
Glycerin Filled Vacuum Gauge
Leak Free Nickel Plated Air Manifold
Brass Barb that will connect to all vacuum pumps
5FT Clear Steel Reinforced Vacuum Hose
8”x8” FDA Grade Silicone Non Stick Pad
50 Micron Air Filter
Homogenizer
This device is used for the homogenization of the platinum silicone material.
Force-Sensing Resistors
This device is a sensor that gives pressure feedback of the force applied to its active area.
ET 493: Senior Design I |Southeastern Louisiana University
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Design
The design of the project will be a skin platform that will consist of an embedded grid of FSRs
that are spatially arranged. The platinum silicone will then be poured on top of the grid. The
FSR will then be tested to calibrate to the appropriate pressure sensory. The array of FSRs will
be able to detect an existence of pressure or external force applied to the surface of the silicone
surface platform.
ET 493: Senior Design I |Southeastern Louisiana University
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Progress
First, research was conducted to understand and choose the appropriate silicone solution for the
project and implementation of electronic devices. Research for the components that will mix,
degas and cure the silicone was conducted. The dragon skin 10 med was found after researching
and purchased through a company online under the webpage: sculpt.com. The gas chamber and
pump were purchased through best value vacuums online. The homogenizer were purchased and
set up.
The project, thus far, is at the stage of testing the platinum silicone. All the materials and
components that will be used to mix the silicone solution are ready to commence
experimentation and testing. This week, our team will start to cure the silicone with different
mixing ratios to produce a final skin-like layer with the optimal thickness and consistency. After
perfecting the artificial skin, then the appropriate size of the platform for testing sensory
feedback will be implemented to the platform. Once the platform has been approved for force
application, the artificial skin will be poured over an array of FSR sensors.
ET 493: Senior Design I |Southeastern Louisiana University
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Deliverables
Task:
Dates:
Progress:
Research Silicone Solution
1/29/2015
Completed
Research De-Gassing
Chamber and Pump
2/05/2015
Completed
Order Silicone Solution
3/05/2015
Completed
Order Chamber and Pump
Completed
Order Homogenizer
Completed
Research FSR sensor
2/10/2015
In Progress
Find team members
3/9/2015
Completed
Set-up work area
3/12/2015
Completed
Set-up De-Gassing Chamber
3/18/2015
Completed
Completed
Set-up Homogenizer
Test Pump
3/20/2015
Completed
Cure Skin Proto-types
3/20/2015
In Progress
Test Skin Proto-types
4/3/2015
Pending
Test FSR Grid
4/8/2015
Pending
Implement FSR Grid
4/15/2015
Pending
Cure Skin Platform
4/22/2015
Pending
Test Skin Platform
4/28//2015
Pending
Implement Platform
Dependent of time
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Measure and Record Data
Dependent of time
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ET 493: Senior Design I |Southeastern Louisiana University
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Works Cited
Ada, L. (2012, July 29). Force Sensitive Resistor-Overview. Retrieved March 25, 2015, from adafruit:
https://learn.adafruit.com/force-sensitive-resistor-fsr
Best Value Vacs. (2014). 3 Gallon Stainless Steel Vacuum Chamber & 3 CFM Single Stage Vacuum Pump.
Retrieved January 24, 2015, from Best Value Vacs:
http://www.bestvaluevacs.com/3gsvackit.html
Fischmann, J. (2014, February 14). Revolution in Artificial Limbs Brings Feeling Back to Amputees.
Retrieved March 25, 2015, from National Geographic:
http://news.nationalgeographic.com/news/2014/02/140222-artificial-limbs-feeling-prostheticsmedicine-science/
Interlink Electronics, Inc. (2015). Datasheets. Retrieved March 25, 2015, from Interlink Electronics:
http://www.interlinkelectronics.com/datasheets/Datasheet_FSR.pdf
Mitchum, R. (2010, December 16). Adding sensory stimulus via robotic arm improves performance of
brain-controlled devices. Retrieved March 20, 2015, from UChicagoNews:
http://news.uchicago.edu/article/2010/12/16/adding-sensory-stimulus-robotic-arm-improvesperformance-brain-controlled-device
The Compleat Sculptor. (n.d.). Platinum Based Silicone Mold Compounds. Retrieved January 26, 2015,
from The Compleat Sculptor: http://sculpt.com/
ET 493: Senior Design I |Southeastern Louisiana University
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