Project 1: Sustainable Electric toothbrush
Leah Frederick
Kelsi McKinley- Lester
Steven Schweigert
Eric Sternberg
March 2, 2012
Team Six
Abstract
Our first design challenge was to create a more sustainable electric toothbrush. The electric toothbrushes currently
on the market are not very sustainable because they do not incorporate environmentally friendly design features
such reusable components and energetically sustainable power generation mechanisms. After assessing customer
needs, the team concluded that the toothbrush design should focus on maintaining performance and user-friendliness
while simultaneously promoting sustainability. These design changes will appeal to consumers who want a quality
toothbrush that is also sustainable.
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1.0 Introduction
1.0.1 Design Task
As a result of recent recycling statistics from the U.S. Environmental Protection Agency, our challenge is to design
a more environmentally sound toothbrush. Many toothbrushes currently on the market contain a lot of excess
materials and lack sustainable power generation.
1.0.2 Design Process
To complete this project, our team must execute a design based on a consumer-needs assessment, external research
into comparable designs and dissection of an Oral-B Cross Action Rechargeable Power Toothbrush.
1.1 Initial Problem Statement
Last year, the U.S. Environmental Protection Agency reported that only 11% of readily recyclable mobile devices
were actually recycled. Our task is to reduce the consumption of natural resources by designing and
environmentally sustainable electric toothbrush.
2.0 Customer Needs Assessment
2.0.1 Customer Needs: Data Collection and Results
To collect data concerning our electric toothbrush design, we created a ten-question survey to learn more about
consumer preferences concerning toothbrushes. We then posted the survey on SurveyMonkey.com and put a link on
Facebook to encourage our friends and peers to take the survey. Because we have a diverse group of friends, the
results were probably not skewed to any personality type. In total about 40 people answered our survey. The survey
questions focused on the consumer’s preferences regarding the performance, portability, and user-friendliness of the
toothbrush. In general, consumers most valued the performance of the toothbrush; they preferred a toothbrush with a
long run time that was effective at cleaning teeth. After performance, consumers valued the user-friendliness of the
toothbrush. This category consisted of things such as comfort, maintenance, ergonomics, and noise level. Few
consumers felt that portability was an important feature; size, weight, and storage all seemed to be second nature to
performance and user-friendliness. Concerning sustainability, the majority of people surveyed responded that they
would pay up to a price of $30 for a more sustainable and “greener” toothbrush. We will be sure to take these
consumer preferences into consideration as we make design decisions.
2.1 Weighting of Customer Needs
Figure 1. Initial Customer Needs List Obtained from Focus Group and Individual
Interviews
Portable
Small
Light
Travel-Friendly
Inexpensive
User-Friendly
Long Battery Life
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Easy to Charge
Cleans Teeth Well
Comfortable to Hold
Comfortable in Mouth
Quiet
Figure 2. Hierarchal Customer Needs List Obtained from Focus Group and Individual
Interviews
1.0 Portability
1.1 Size: Small
1.2 Weight: Light
1.3 Storage Options: Comes with Cover
1.4 Travel-Friendly: Foldable
2.0 Performance
2.1 Battery Run Time: Long Battery Life
F.1 Cleanliness of teeth: Works well
3.0 User-Friendliness
3.1 Comfort: Gentle on Gums/Mouth
3.2 Electronic Maintenance: Easy to replace battery or charge
3.3 Physical Maintenance: Easy to replace bristles
3.4 Ergonomics: Comfortable Handle
3.5 Noise Level: Quiet
C.1 Low Cost
Figure 3. AHP Pairwise Comparison Chart to Determine Weighting for Main Objective
Categories
Portability
Performance
1.00
8.00
4.00
0.13
1.00
0.50
1.0 Portability
2.0 Performance
3.0 User-Friendliness
UserFriendliness
0.25
5.00
1.00
Total
Weight
1.38
14.00
5.50
0.07
0.67
0.26
Figure 4. AHP Pairwise Comparision Chart to Determine Weighting of User Friendly
Sub-Objectives
Size
1.1 Size
1.2 Weight
1.3 Storage
1.4 Travel-ability
1.00
2.00
1.00
0.25
Weight
Storage
0.50
1.00
0.50
0.17
1.00
2.00
1.00
0.25
Travelability
4.00
6.00
4.00
1.00
Total
Weight
6.50
11.00
6.50
1.67
0.25
0.43
0.25
0.06
Figure 5. Weighted Hierarchal Customer Needs List Obtained from Focus Group and
Individual Interviews
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3.1 Comfort
3.2 Electronic
Maintenance
3.3 Physical
Maintenance
3.4 Ergonomics
3.5 Noise
Comfort
Electronic
Maintenance
Physical
Maintenance
Ergonomics
Noise
Total
Weight
1.00
5.00
5.00
5.00
7.00
26.10
0.20
1.00
1.00
0.50
2.00
7.90
0.44
0.13
0.20
1.00
1.00
0.50
2.00
8.00
0.20
0.14
2.00
0.50
2.00
0.50
1.00
0.33
3.00
1.00
11.60
5.98
0.13
0.19
0.10
Figure 6. Weighted Customer Needs List
1.0 Portability (0.07, 0.07)
1.1 Size: Small (0.0175,0.25)
1.2 Weight: Light (0.0301,0.43)
1.3 Storage Options: Comes with Cover (0.175,0.25)
1.4 Travel-Friendly: Foldable (0.0042,0.06)
2.0 Performance (0.67,0.67)
2.1 Battery Run Time: Long Battery Life (0.67,1.0)
F.1 Cleanliness of teeth: Works well
3.0 User-Friendliness (.26,.26)
3.1 Comfort: Gentle on Gums/Mouth (0.2948,0.44)
3.2 Electronic Maintenance: Easy to replace battery or charge (0.0338,0.13)
3.3 Physical Maintenance: Easy to replace bristles (0.0338,0.13)
3.4 Ergonomics: Comfortable Handle (0.006422,0.19)
3.5 Noise Level: Quiet (0.026,0.10)
C.1 Low Cost
3.0 Revised Problem Statement
Our design problem is to design an inexpensive electric toothbrush that, above all else, functions well. Considering
customer needs, we have determined that the design must have a long battery life and must be fairly user-friendly.
Our team has decided to focus on minimizing the quantity of materials used in the toothbrush body and power
usage.
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4.0 External Search
Before generating concepts, we conducted internal and external research by investigating current design patents,
learning about sustainable materials, and dissecting an existing on-the-market electric toothbrush.
4.1 Literature Review
For the overall brush design, we researched sustainable toothbrushes already in existence. Many sustainable
toothbrushes are made out of recyclable plastics or bamboo. The most easily recycled plastics are plastics labelled
one through three, however, these plastics are not very durable and would not be practical for a durable toothbrush
design. Therefore, we widened our search scope and discovered that number five plastics, which are strong enough
for toothbrush use, are being accepted by more and more curb-side recycling services and recycling centers which
therefore makes the use of number five plastic viable. (Dunn, 2012)
When investigating the brush head, we focused on the bristle designs. We found that dentists favor soft nylon
bristles because hard bristles cause the gum lines to recede and nylon is resistant to bacteria build-up (Conjecture
Corporation, 2011). Unfortunately, nylon cannot be recycled and thus is not environmentally sustainable. We
found numerous “sustainable” toothbrushes that featured natural bristles. However, natural bristles are created from
boar’s hairs and boar hair has an affinity for bacteria and becomes unsanitary very quickly (Conjecture Corporation,
2011). Therefore, in order to keep the mouth and teeth healthy, one would need to replace the bristles much more
often. One toothbrush from Australia, “The Environmental Toothbrush”, claims to have biodegradable bristles but
does not mention the material used in their bristles (Go Green at Home, 2012). We also discovered ECM Biofilm
which is a biodegradable plastic substance (ECM Biofilms, 2012). The Biofilm could be used for bristles or for
packaging.
Another option is to have replaceable toothbrush heads and we found evidence of many manual
toothbrushes that had replaceable toothbrush heads (ECO-Dent, 2011). However, electric toothbrushes with
removable heads did not appear in our research indicating that not many companies produce electric toothbrushes
with removable heads.
In terms of accessories, we discovered that some companies send envelops with their toothbrushes so the
consumers can send back the recyclable materials and the company recycles the plastic (Preserve, 2012). We also
examined the Energy Star program’s website for ideas to reduce power usage. Although we did not find any
concrete examples dealing with toothbrushes, we learned that a lot of devices continued to use energy when they are
plugged in—regardless of whether or not they need to be using that power for charging. This phenomena has been
referred to as “vampire energy” (ENERGY STAR, 2010).
.
4.2 Patent Search
Figure 7. Oral-B Cross Action Electric Toothbrush
Clean the teeth
Competitive Patent
Brush Head
US
D/268,028
Part
Overall Toothbrush
Battery Powered Toothbrush
Rotating Bristles
US
6,178,579 B1
General Patent
Evenly Cleans teeth
US 20060112505A1
US
20026735804
The process of finding patents was relatively simple on this particular device. Google offers a service which allows consumers to
directly look the basic components of a devise and will inform you of any specific patent. The patents that we have found directly
from Oral-B were on the Brush Head and the rotating bristles (cross action bristles) on the brush head. These patents are only to
be used for and by Oral-B products. On the other hand we found that there are general patents on both the original toothbrush
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design and also the electric toothbrush. These are put in place to keep the field open and fair on a product as simple as a
toothbrush.
4.3 Benchmarking
Figure 8. Benchmarking of Four Products
Feature
Packaging
Aesthetics
Ease to clean
Convenience of on/off switch
Travel Size
Effectiveness
Price
Oral-B
3
4
4
4
3
4
4
Crest Spinbrush
5
2
3
4
4
3
5
Colgate
3
3
3
4
3
4
4
Reach
2
4
4
5
2
5
3
The scale that we have chosen for benchmarking was from 1-5, where 5 is the highest and 1 is the lowest rating.
Based on reviews of consumers and our personal opinions we weighed the Oral-B toothbrush’s features to those of 4
other leading comparing that are in the same price range. The features we focused our attention on was mainly the
packaging, aesthetics, easiness to clean, convince of an on/off switch, travel size, effectiveness, and price. Viewing
different websites, we accumulated a decent amount of information on what we like and also what the consumers
want. Based on our scales and research, our newly designed brush should resemble the features in the Crest
Spinbrush.
4.4 Product Dissection
In Lab 2 we used instruments to measure specific functions of the toothbrush such as noise level and power. We
took several measurements with different variables and came up with the following results:
Location:
Brush head 4 in away from decibel meter
Brush head 3 in away from decibel meter
Brush head 2 in away from decibel meter
Brush head 1 in away from decibel meter
DC motor 4 in away from decibel meter
DC motor 3 in away from decibel meter
DC motor 2 in away from decibel meter
DC motor 1 in away from decibel meter
Noise Level (dB)
83.5
85.8
86.3
87.1
78.7
79.3
80.3
81.5
Figure 9. Noise Level Data of Oral-B Toothbrush
NOTE: Background noise = 60 dB
Approximate duration of brushing per day: 4 minutes
Average noise level during brushing: 82 dB
Following the noise measurements, we dissected the toothbrush and removed the battery to take measurements of its
electric potential and power under a certain load. The results were as follows:
Average Voltage: 1.12 V
Average Current under No Load: .37 Amps
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Average Current under Load: .42 Amps
Power (no load) = (1.12 Volts)(0.37Amps) = .41 watts
Power (under load) = (1.12 V)(0.42Amps) =.4704 watts
From our measurements on the battery we were able to calculate the battery life:
Number of hours available per single battery ‘under load’ conditions: 2.38 Hours
Estimate duration for each brushing: 0.0333Hours x 2 Times/Day= 0.0666
Number of days before battery replacement: 36.5 Days
4.5 Design Target
After external research and a customer needs assessment our team’s design target is to create a more sustainable
toothbrush and one that caters to the needs of our customers. By making our toothbrush more sustainable, we hope
to limit energy consumption and also use a more energy efficient process. We also hope to limit materials and
design our toothbrush in such a way to do this. From our customer needs assessment we learned that in general,
consumers preferred a tooth brush that performed well over anything else. Therefore, our mission to create a
toothbrush that does the best possible job of cleaning teeth in a comfortable manner while at the same time being
environmentally sustainable.
5.0 Concept Generation
5.1 Problem Clarification
Figure 10. Problem Clarification Diagram
5.2 Concept Generation
There are our primary ideas (see Figure 11):
5.2.1 Power Generation and Accessories
Small Battery: using a smaller battery that must be charged each use would reduce the size of the toothbrush and the
amount of materials needed
Incorporate cord directly into toothbrush: like a hair dryer, the consumer would just plug the toothbrush directly
into the wall. This would eliminate energy lost in the conversion process.
5.2.2 Brush Head Design
Brush Head Pads Removable: this would cut down on the materials that need to be thrown out or recycled
Biodegradable Bristles: would make it more sustainable
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5.2.3 Energy Mechanism
Shorter rod: makes the oscillation faster
Piston instead of rod: maximizes power
5.2.4 Body Design and Human Factors
Smaller Diameter: make the toothbrush body as small as possible to minimize materials
Incorporate holes in design: Minimizes materials
Figure 10. Chart of Major Concepts
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6.0 Concept Selection
Energy Mechanism
Brush Head Design
Human
Factors/Body Design
Package in ecofriendly materials
such as recycled
cardboard
Shorter rod for oscillation
which leads to faster toothbrush
speed because short period of
revolution.
Bristle pointing in
three directions to
increase brushing ability
Oscillation moves two
independent brush head pieces
for greater cleaning power.
Bristles change color
with wear so the user
knows exactly when the
bristles need to be
replaced
Build body from
eco-friendly materials
such as hemp/wood
composite
Removable Bristle
pads that can be locked
into place through a
twisting motion
Smallest possible
toothbrush diameter
(size of battery)
Free-moving brush heads that
are only held in place by one
pivot point so the user can still
clean their teeth without turning
on the toothbrush
A sliding power intensity
button on the toothbrush’s side to
allow consumers to choose their
level of cleaning
Larger battery to reduce the
charging frequency
Power Generation
Attach a cord to the
toothbrush body so the
toothbrush no longer
requires a battery
Incorporate an on/off
switch into charger so
that energy is not wasted
when the device is not in
use
Charge with a kinetic
energy system similar to
a shakable flashlight
Vibrating tongue
cleaner on the
toothbrush’s reverse side
Hollow toothbrush
Hollow charger to
reduce material usage
Two brush heads that
rotate in opposite
directions
Finger grips
molded into the body
Retractable charge
cord in base
Figure 12. Morphological Chart
Our pugh charts (see Figure 13) for each functional group (body design, power, energy mechanism, and brush head)
appear in Figure 6. In the body design pugh chart, the fingers grips were the best concept since they were the most
ergonomic and didn’t require any extra materials. Our best concept was in the power functional group. We decided
upon a shake charger, like an emergency flashlight. This design was ultimately easier to use than a direct cord or a
standard changing station. In our energy mechanism group, the pivoting brush head was ranked highest because it
would eliminate the most noise. We eventually decided that this design would require more materials and moving
parts than were sustainable. In the brush head chart, opposite rotating heads was the best concept since it would not
add any extra size or physical maintenance. Overall, we decided to base our design mostly upon our concept of a
charging mechanism requiring a shaking motion. This design was the most sustainable (doesn’t need to be charged
with an electrical outlet) and simplest for the user to use.
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Function: Body Design and Human Factors
Customer Needs
Size
Weight
Ergonomics
Weighting
0.02
0.03
0.05
Concept 1: Smaller Toothbrush Diameter
1.00
1.00
-1.00
Concept 2: Cut-Outs to Conserve Materials
0.00
0.00
0.00
Concept 3: Finger Grips
1.00
-1.00
1.00
Function: Power
Battery Run Time
0.67
0.00
0.00
-1.00
Customer Needs
Weighting
Concept 1: Shake
Concept 2: Direct Cord
Concept 3: Switch on Charging Station
Electronic Maintenance
0.03
1.00
0.00
0.00
Sum
Rank
-0.0018
0.00
0.0368
3
2
1
Sum
Rank
0.03
0.00
-0.67
1
2
3
Function: Energy Mechanism
Customer Needs
Performance
Weighting
Concept 1: Shorter Oscillation Rod
Concept 2: Two moving bristle sets
Concept 3: Brushead Pivots
0.67
-1.00
0.00
0.00
Noise Level
0.03
-1.00
0.00
1.00
Sum
Rank
-0.696
0.00
0.026
3
2
1
Function: Brush head
Customer Needs
Size
Comfort
Weighting
0.02
1.00
2.00
0.00
0.11
Physical
Maintenance
0.07
2.00
-1.00
-1.00
0.00
2.00
0.00
0.1437
0.06
0.00
1.00
1.00
1.00
0.20
2.00
-2.00
-2.00
Concept 1: Bristles pointing in 3 different directions
Concept 2: Replaceable/Removable Bristle Pads
Concept 3: Bristles that change color with wear
Concept 4: Two bristle pads that rotate in opposite
directions
Concept 5: Vibrating tongue cleaner on opposite side
Figure 13. Pugh Charts for each functional group
10
Sum
-0.399
Rank
2
3
4
1
5
7.0 Final Design
The final toothbrush model, Green Clean, is a compilation of the best design concepts. The primary feature is its
sustainable method of charging; the user simply shakes the toothbrush, like an emergency flashlight, to provide the
energy needed for the toothbrush to run. The physical body of the toothbrush is design was made sustainable by
including cut-outs and hollow sections to minimize materials and having concave grips. These feature reduces the
materials necessary while still retaining a customer-friendly size and weight. The toothbrush uses a standard sized
replaceable brush head, again reducing the environmental footprint while maintaining customer needs. Lastly, the
Green Clean is made of green and white plastic to promote its sustainability. See section 7.1.1 for final design
SolidWorks drawings.
7.1 Design Drawings, Parts List and Bill of Materials
7.1.1 Final Design Drawings
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Figure 14. SolidWorks Drawings of Final Toothbrush Design
7.1.2 Bill of Materials
Part
#
Part Name
Quantity
SOP
Effect
1
Body
1
No
2
Grip
1
No
3
Capacitor
Neodymium
Magnet
Coil
1
No
Holds main
parts of
toothbrush
Provides
Comfort to
User
Power
1
No
1
No
4
5
6
Bridge
Rectifier
1
No
7
Toothbrush
Head
1
No
8
Bristles
1
No
Material
Manufacturing
Process
Dimensions
Plastic
Injection
Molding
5 in x .5 in
radius
Rubber
Injection
Molding
2 in x .5 in
radius
Metal
Casting
n/a
Power
Metal
Casting
n/a
Power
Converts
negative
pulses to
positive
pulses
Holds
Bristles
Cleans
Teeth
Wire
Casting
n/a
Electric
Component
Assembly
n/a
Function
Plastic
Plastic
Figure 15. Bill of Materials Table
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Injection
Molding
Injection
Molding
1 in
n/a
7.2 How does it work?
The Green Clean toothbrush functions similarly to any other toothbrush. It is designed to clean your teeth and leave
you with a beautiful shining smile. Despite this, there is one important detail that is different. Regular electric tooth
brushes are powered by regular AA batteries or by rechargeable batteries that are charged through a charging station
that is plugged into the wall. The Green Clean uses an alternative form of energy to make it a more sustainable
toothbrush. The Green Clean uses a mechanism similar to a “shake” emergency flashlight. The idea behind this
system comes from a coil of wire and a magnet. By shaking the toothbrush, the magnet slides back and forth inside
the tube and generates a pulse of electricity in the coil. The toothbrush also uses an alternative to a battery called a
capacitor. Capacitors are very similar to batteries in that they can store charge, but the advantage is that they can be
charged almost instantly with just a few shakes. Finally, an important part called a bridge rectifier converts negative
electrical pulses to positive pulses ensuring that all of the energy is in one direction. This ingenious method was
discovered by a scientist named Michael Faraday and is a proven method to generate enough power for an electric
toothbrush. This gives us an excellent alternative power source to make our toothbrush more sustainable.
8.0 Conclusions
The final design was a success: the toothbrush was made more sustainable while maintaining the performance
quality and user-friendliness of the product. Since most of the toothbrush’s exterior and ergonomic features are the
same as current, non-eco-friendly toothbrushes, we have succeeded in creating a toothbrush that has a smaller
footprint without diminishing other features. For example, we hollowed out the excess material in the body design,
so as to use less material yet maintain the ergonomic shape. The most unique and most sustainable feature of the
Green Clean toothbrush is that it charges through shaking. This design eliminates the need for any type of electrical
charging station or replaceable battery. Most of all, this first design project was a success in teaching the process of
redesigning a product with many diverse engineering aspects.
References
Conjecture Corporation, "What are the Different Types of Toothbrush Bristles?." Last modified January 01, 2012 .
Accessed March 1, 2012.
Dunn, Collin. Discovery Communications, LLC, "Get to Know Your Recyclables ." Last modified 2012. Accessed
March 1, 2012.
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Eco-Dent Premium Natural Oral Care Products, "Replaceable Head Toothbrush." Last modified March 07, 2011.
Accessed March 1, 2012.
ENERGY STAR, "About ENERGY STAR." Last modified 2010. Accessed March 1, 2012.
Go Green at Home, "About the Environmental Toothbrush." Last modified 2010. Accessed March 1, 2012.
"How Faraday Flashlights Work." Shake Flashlights Info. ShakeFlashlights.com , 2011. Web. 1 Mar 2012.
<http://www.shake-flashlights.com/how-they-work.html>.
"How Stuff Works ." Inside a Shaker Flashlight. Discovery Channel, 10 30 2008. Web. 1 Mar 2012.
<http://express.howstuffworks.com/autopsy-shaker-flashlight.htm>.
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