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USER

MANUAL

Team Soft Robots Jillian Redmond, Keegan McKim, Stefan LaRose,

Bethany Schulberg

Department of Chemical and Biological Engineering

April 28, 2017

User Manual Page i

TABLE OF CONTENTS

1.0 GENERAL INFORMATION ................................................................................................... 1

1.1 Introduction ......................................................................................................................... 1

1.2 Safety Information............................................................................................................... 1

2.0 QUICK START GUIDE ........................................................................................................... 2

3.0 PROCESS OF FABRICATION ............................................................................................... 3

3.1 Fabrication of Tentacle.......................................................................................................... 3

3.1.a SolidWorks Files............................................................................................................. 3

3.1.b Wax Inserts ..................................................................................................................... 4

3.1.c Tentacle Casting ............................................................................................................. 5

3.2 Fabrication of Large Claw..................................................................................................... 7

3.2.a SolidWorks Files............................................................................................................. 7

3.2.b Wax Inserts ..................................................................................................................... 8

3.2.c Large Claw Casting ........................................................................................................ 9

3.3 Fabrication of Small Claw................................................................................................... 10

3.3.a SolidWorks Files........................................................................................................... 10

3.3.b Wax Inserts ................................................................................................................... 11

3.3c Small Claw Casting ....................................................................................................... 12

4.0 USING THE SYSTEM ........................................................................................................... 13

5.0 MAINTENANCE ................................................................................................................... 14

6.0 TROUBLESHOOTING .......................................................................................................... 15

7.0 FUTURE WORK .................................................................................................................... 16

8.0 BUDGET ................................................................................................................................ 18

8.1 Purchased Items................................................................................................................... 18

8.2 Acquired Items .................................................................................................................... 18

9.0 GLOSSARY ........................................................................................................................... 19

10.0 ACKNOWLEDGEMENTS .................................................................................................. 20

1.0 General Information

User Manual Page 1

1.0 GENERAL INFORMATION

1.1 Introduction

Soft robotics is a new field within science that earned its official group standing from the IEEE

RAS Technical committee in 2012. The intentions of soft robots are to have a large range of

motion to allow for bending, twisting, contracting and flexion, movements of a human or

animal. Slippery liquid-infused porous surfaces, also referred to as SLIPS, is a new approach to

design synthetic slippery surfaces that can repel various liquids. SLIPS Technologies, a start-up

company in Cambridge, Massachusetts, has worked to create a new polymer to combine soft

robotics and the slippery surfaces into a robot that mimics functionality as a human

organism. The SLIPS Technology allows for individuals to no longer have to choose between

elastic deformity or a lack in mobility when creating a soft robot.

1.2 Safety Information

The production of a soft robot requires usage of a heating plate to melt wax for molding. Wear

appropriate protection such as goggles and heat resistant gloves to prevent burning oneself.

When using EcoFlex, do not ingest either Part A, Part B, or the mixture, and rinse any area of the

body that comes in direct contact with the EcoFlex immediately. In the case of eye

contamination, rinse with water and seek medical attention if irritation persists. In the case of

skin contamination, rinse with soap and water then clean clothing items that are contaminated

before reuse.

3.0 Process of Fabrication

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2.0 QUICK START GUIDE

8 7 6

5 4

3 2 1 Assemble wax prongs

in desired formation

Place wax assembly

within 3D printed mold

Mix and pour Ecoflex in

the mold around the wax

After 6 hours, suspend mold

in oven to melt wax

Upon removal of the wax, the

robot is ready to actuate

Caulk the actuation tube to

the center hole of the robot

Allow the caulking to

dry for at least 30 min

Attach tubing to pressure

gauge and actuate at 1-2 psi


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3.0 PROCESS OF FABRICATION

3.1 Fabrication of Tentacle

3.1.a SolidWorks Files

Download STL mold files from http://www.thingiverse.com/thing:92103/#files in the Thing

Files section as shown below.

Print at 50% the original size. Three of the trefoil parts will need to be printed which can be done

all at once.

http://www.thingiverse.com/thing:92103/#files


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3.1.b Wax Inserts

In order to create the wax inserts, a EcoFlex mold of the wax mold must be made. Mix 83 mL of

EcoFlex. Fill PLA wax insert mold with the EcoFlex Mixture and allow to solidify for 4-6

hours.

Pour wax into the mold until it is filled completely (approx. 19 mL). Let solidify for

approximately 15 minutes. Carefully remove solidified wax inserts.


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3.1.c Tentacle Casting

To begin casting the tentacle, caulk and screw two trefoil pieces

together. Insert the wax prongs into the wax base by connecting

with melted wax. Hang the wax as straight as possible in the

center of the trefoil tentacle mold.

IMPORTANT: The trefoil mold is not airtight. It is necessary

to caulk all seems and screw holes. Use basic silicone caulking

and wait 30 minutes before pouring the EcoFlex

In a beaker, weigh 14 g of Part A EcoFlex. Mix 14 g of Part B

EcoFlex with Part A thoroughly. Pour the mixture around the

wax ensuring it is completely covered. Allow EcoFlex to

solidify for 4-6 hours.

Note: Creating a hole in the middle of the wax base will allow

for an easier pouring process.


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Carefully remove the tentacle from the mold by peeling the

caulking from the seams and removing the screws. Hang

tentacle in an oven over a container to collect the wax.


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3.2 Fabrication of Large Claw


SolidWorks files to use as a mold for the wax inserts and for the casting of the small claw were

designed and created. Images of these files can be seen below.

Using an Ultimaker 3D printer with Cura Software, the molds were printed in PLA for use.


User Manual Page 8

3.2.b Wax Inserts

In order to create the wax inserts, a EcoFlex mold of

the wax mold must be made. Mix 112 mL of EcoFlex.

Fill PLA wax insert mold with the EcoFlex Mixture

and allow to solidify for 4-6 hours.

Remove EcoFlex wax mold from PLA mold. In a

beaker, melt paraffin wax until liquefied. Pour wax into

the mold until it is filled completely (approx. 19 mL).

Let solidify for approximately 15 minutes. Carefully

remove solidified wax inserts.


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3.2.c Large Claw Casting

Solder the wax sticks into the square center using more

wax. Place the wax cross insert into the claw mold using a

small amount of melted wax in the central hole to anchor

the wax in place.

In a beaker, weigh 37 g of Part A EcoFlex. Mix 37 g of

Part B EcoFlex with Part A thoroughly. Pour the mixture

around the wax ensuring it is completely covered. Allow

EcoFlex to solidify for 4-6 hours.

Carefully remove the claw from the mold. Hang claw

(central hole side down) in an oven over a container to

collect the wax as it melts from the mold.


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3.3 Fabrication of Small Claw


SolidWorks files to use as a mold for the wax inserts and for the casting of the small claw were

designed and created. Images of these files can be seen below.

Using an Ultimaker 3D printer with Cura Software, print the mold with PLA.


User Manual Page 11

3.3.b Wax Inserts

In order to create the wax inserts, a EcoFlex mold of the

wax mold must be made. Mix 112 mL of EcoFlex. Fill

PLA wax insert mold with the EcoFlex Mixture and

allow to solidify for 4-6 hours.

Remove EcoFlex wax mold from PLA mold. In a

beaker, melt paraffin wax until liquefied. Pour wax into

the mold until it is filled completely. Let solidify for

approximately 15 minutes. Carefully remove solidified

wax inserts.

For use in the small claw mold, cut 2 sections off the

wax prongs. Solder the wax sticks into the square center

using more wax, it will look like a cross as depicted to

the right.


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3.3c Small Claw Casting

Place the wax cross insert into the claw mold using a

small amount of melted wax in the central hole to

anchor the wax in place.

In a beaker, weigh 31.5 g of Part A EcoFlex. Mix 31.5 g

of Part B EcoFlex with Part A thoroughly. Pour the

mixture around the wax ensuring it is completely

covered. Allow EcoFlex to solidify for 4-6 hours.

Carefully remove the claw from the mold. Hang claw

(central hole side down) in an oven over a container to

collect the wax as it melts from the mold.

4.0 Using the System

User Manual Page 13

4.0 USING THE SYSTEM

Manipulation of any soft robot requires control over the input and output of air to control flexion.

Solenoids are the standard method to block or allow flow of air by providing a desired voltage to

induce the solenoids open position. The combination of LabVIEW and a RW Automation board

allows for TTL (Transistor transistor logic) of the solenoid. This means that by toggling the

digital outputs on a myDAQ one can control the state of the solenoid. In the case of the tentacle

three solenoids were required to dictate direction of actuation, with a bleed valve included to

release built up pressure. For a claw only a single solenoid is needed assuming all prongs actuate

simultaneously. This allows for a simple LabVIEW program with a boolean switch acting as the

control for dictating actuation.

5.0 Maintenance

User Manual Page 14

5.0 MAINTENANCE

Assuming the validity of the self-cleaning and self-healing properties of SLIPS polymer little

maintenance is required for the soft robot itself. However, the actuation tubing presents the risk

of being ripped loose due to the pressures used. Therefore, reapplication of silicone caulking

around the tube entry point after identification of potential cracks or damage is the only major

maintenance required. Other potential tasks that may include cleaning and care of the air

compressor or re-tubing following signs of tube deformation or breakage.

6.0 Troubleshooting

User Manual Page 15

6.0 TROUBLESHOOTING

1) The tentacle structure is leaking: After inserting the wax mold to the SolidWorks printed

mold the polymer is leaking

The 3D printed mold was not sufficiently air-tight

Dispose of leaking mold and use caulking to provide air-tight seal

2) The wax insert is floating up during the drying process of the claw: As EcoFlex is added

to the claw mold, the wax insert rises to the top of the mold

Add a small amount of hot wax to the central peg hole to anchor the wax insert to the

claw mold

3) Wall thickness is inconsistent: Due to the wax insert shifting upon being poured, the

actuation is inconsistent

Decrease the claw arm by half to allow for less shift in the wax inserts

Seek alternative to wax to ease handling (e.g. InstaMorph)

4) The air compressor pressure exceeds what the soft robot can handle.

Purchase a pressure regulator that allows you to lower the pressure when air actuating the

robot

5) Caulking bursts upon actuation: Excessive use or high pressure causes caulking wear and

breakage

Remove used caulking and recaulk the tube to the robot

Seek alternative adhesive to caulking that provides a stronger seal (e.g. glue, liquid

cement)

7.0 Future Work

User Manual Page 16

7.0 FUTURE WORK

A procedure for creating a seamless soft robot that functions as a mechanical claw was

successfully designed and carried out. However, successfully actuating the claw to create a

grabbing motion was never fully achieved. It was speculated that this lack of functionality was

due to inconsistencies in the wax prong suspension, inconsistencies in the wall thickness of the

claw, and the design of the wax prongs not sufficiently directing the actuation of the claw arms.

These flaws present themselves in the final product by causing the claw arms to actuate in

random directions, resulting in an unpredictable final actuation state.

The wax prongs proved to be the crux of creating a functioning seamless soft robot. They were

very brittle, and broke often when attempting to manipulate them in the 3D printed molds. In

addition, if the wax prongs were not perfectly straight in the x-, y-, and z-directions then the

resulting wall thickness in the final claw would not be consistent, resulting in improper actuation.

One alternative that helped in creating a more consistent product, but did not solve the problem

altogether was decreasing the length of the arms of the claw. An alternative solution that was

proposed was to find a substitute for the wax that can also be easily removed after the EcoFlex

cures. An option was discovered (but was unable to be purchased due to budget conflicts) was

InstaMorph moldable plastic. In videos provided by the company, it seemed much easier to work

with than the paraffin wax and is able to be boiled out of the molds (similar enough to the

melting of wax). This should be considered for creating the interior hollow chambers of any new

design created in place of the wax, as it may provide a more consistent wall thickness.

The notches that are seen in the wax prongs, provided by the personalized design of the 3D

printed mold, are intended to focus the direction of actuation of the claw arms. As seen in the

tentacle prototype, the notches allow for increased extension due to the space created between

them, causing the robot to bend away from the side with the notches. However, when attempting

to actuate the seamless claw arms the notches provided by the wax prongs did not seem to help

them bend in the correct direction. A recommendation for this issue would be to experiment with

using different notching methods to see what design is optimal. It is possible that increasing the

7.0 Future Work

User Manual Page 17

number of notches in the prongs would increase their ability to direct the claw arms. This

prediction was based on the observation that the tentacle, with far more notches in the prongs,

actuated much more appropriately than the prongs design for the claw.

Upon creating a soft robot that actuates in the desired direction, several advancements have been

theorized for future work. One advancement would be to include solenoids within the arms of the

soft robot to allow different regions of the robot to actuate individually, increasing its versatility.

Another important aspect of this project that should be performed in the future is to conduct

strength tests to determine what objects the robot will be able to manipulate. The graphs used in

this project were strictly theoretical, and were provided by other soft robot creators. It would be

very helpful to create a set of data specific to the seamless soft robots created in this project.

Finally, a modification to the design of the claw that may help in grabbing objects would be to

increase the width of the prongs in order to increase the contact surface area. This would mean

increasing the width of the wax inserts as well, and may be an interesting challenge to help the

robot grasp various objects.

8.0 Budget

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8.0 BUDGET

8.1 Purchased Items

Product Number Product Name Quantity Cost Company

B008GRTSV6 Arduino Uno R3 Microcontroller A000066 1 $19.99 Arduino.org/Amazon

15133960 1 LB. Ready-Blend Candle Wax 1 $3.74 Joann

B004KNBVM4 Air Compressor 1 $80.00 Lowes

997 Solenoid 1 $6.95 Amazon

B00ATEAMXW EcoFlex Silicone 00-30 1 $30.10 Smooth-on

6763K82 Aluminum Housing W/ Pressure Gauge 1 $42.57 McMaster Carr

5233K54 Silicone Tubing 25 ft. $8.25 McMaster Carr

5016K488 Connectors 2 $10.32 McMaster Carr

Silicone Caulking 1 $5.00 Aubuchon

Total $206.92

8.2 Acquired Items

Product Name Quantity Cost Company

PDMS 420 g $64.00 Howell Labs

PLA 466.6 g $24.70 CHB Department

RW Automation SC5 1 $180 CHB Department

http://arduino.org/Amazon

9.0 Glossary

User Manual Page 19

9.0 GLOSSARY

Slippery Liquid Infused Porous Surface (SLIPS): A polymer capable of repelling fluids and

biological fouling agents by using an immobilized liquid layer.

Soft Robot: Non-rigid, functional structures that are constructed with deformable materials that

can be mobilized by gaseous or liquid substances to perform specific tasks.

Tentacle: First soft robot prototype, incorporating three internal chambers surrounded by

silicone, creating a cylindrical model that exhibits 360° of flexion.

Actuation: Providing the interior chamber(s) of the soft robot with air at a specific pressure to

create flexion.

Seamless: Method of soft robot creation that eliminates binding and surface interaction issues by

casting all at once.

Ecoflex: Elastic polymer used to model the SLIPS polymer.

Solenoid: Electromechanically operated valve used to control the flow of air or water into the

soft robot.

LabVIEW: Software program used to control external electronics and devices.

SolidWorks: Three dimensional CAD software used to design molds and model potential force

interactions.

PDMS: Polydimethylsiloxane; material that models that function and characteristics of SLIPS

polymer.

Claw: Final design for the soft robot intended to grasp fragile objects such as an egg, or Jello

cube.

10.0 Acknowledgements

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10.0 ACKNOWLEDGEMENTS

Thank you to Phil Kim of SLIPS Technologies for support and feedback, Caitlin Howell, Angel

Hildreth, Jonathan Overton, and Karissa Tilbury for ordering supplies and providing guidance, as

well as the Department of Chemical and Biological Engineering for financial support of this

work.

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