Concept generation never comes easy; after many failed designs, user conversations, and changes to evaluation criteria, learn about our first successful preliminary design and the screening process involved.
DBTL #3
Considering requirements must also include that the tool does not interfere with the pipetting, we documented what aspects of the pipette mustn’t be interfered with. We also performed the second round of C-sketches.
With our user, we made modifications to our WDM, and created satisfaction curves based alongside our user that will then be used to evaluate our designs. A conversation with our co-PI clarified our WDM.
Using our new WDM, we screened our C-sketches to determine which one we should print.
We learnt which C-sketch we should move forward in designing our CADs.
Decision Framework #3
We consulted with our wet lab members and Dr. Usprech about must-have aspects of a pipette that if an add-on interferes with, will automatically fail that c-sketch. We added screening requirements as after conversing with our the wet lab team and classified them, respectively: requirements that are considered a given, those that are clearly stated and those that could rise eventually but may not be as pertinent at the moment.
Table 6: Classified Pipette Functionality
Threshold
Expressed
Latent
must press down on piston
doesn’t affect pipetting force
Can be sterilized with UV
must have access to both steps of piston
being able to mix fluids using the pipette
can still be placed to the table without tip touching table
must be able to have tip enter liquid
Nice ejection
can still be hung on the pipette box
piston is able to shoot up
Does not interfere with ejection
doesn’t affect range of motion
Picks up fluid and dispenses fluid
must be able to be sterilized with ethanol, fully sealed material
not a flammable material
must not absorb fluids
the pipette’s tip remains not bulky
must see the volume size
doesn’t block the lock
The above pipette functions were classified as pass/fail requirements, because if the tool interferes with the pipettes function, our stakeholder will be unable to use our tool. Therefore all pipette function requirements must pass by acting the same as a regular pipette in all regards.
The following factors are appreciated in design but are not formally scored to fail or pass a design in the screening round (ie. they are a “nice to have” (N)).
Must be able to change volume with one hand (N)
Material won’t soften if hot (N)
Can still be hung on the pipette box (N)
Can still be placed to the table without tip touching table (N)
Can be sterilized with UV (N)
iHP conversation
Upon meeting with Mr. Bumbulovic, we shared with him the need for a lightweight add-on according to our user interview and shared our ideas about using a lightweight foam. Our only concern was our potential inability to sterilize the foam, to which he highlighted the use of polyurethane. Polyurethane is known to be lightweight, affordable, environment-friendly, and yet both durable and versatile according to further research that we then did. There are also many types, allowing us to choose what works best for our user.
Mr. Mladen Bumbulovic
P. Eng, Director of Technical Services, Physics and Astronomy
C-Sketch Round #2
Because all of our previous designs failed preliminary screening, before moving onto the “Build” step of DBTL, we conducted a second round of c-sketching.
Table 5: Round 2 Descriptions
Design
Description
A
Material is inspired by Eppendorf’s reduction in pipette weight by 20% by using ethylene-propylene-diene for their micropipettes. The wrist add-on from Design J (round 1) was made slightly longer to provide better immobilization. It can be rotated/removed to go back to using the wrist if needed (flexible). To reduce repetition, the wrist extension prevents wrist use and instead forces the user to use their shoulder subconsciously; this immobilization factor is similar to those in CTS braces. Using the shoulder prevents repetition and overuse, a factor stressed by Dr. Backman to aid individuals with rheumatory arthritis.
B
A silicone sleeve that can be pulled onto the pipette. It will have thicker and thinner silicone portions that are distributed asymmetrically so that the user may rotate the sleeve to the position that is mot comfortable. There will also be texture on the surface, to increase grip. There will also be a drawn design on the surface to increase the appeal of the tool.
C
Design C consists of an ergonomic adaptation for the palm, better fitted to the shape of one’s hand. In addition, this design includes a brace support to alleviate weight from the wrist by redistributing the weight to the forearm while also allowing the user to loosen their grip without worrying about dropping the pipette: the pipette can be placed into a hook and sits, while the other end extends to a brace on the forearm.
D
Design D consists of two adaptation: a lever for turning the knob, and an ergonomic hand mold. The lever utilizes torque fundamentals; by extending the lever, less force is needed to turn the knob. The ergonomic hand mold better adapts to the human hand, by providing comfort in the indent of the palm, better fitting a hand’s natural position. The hand mold also increases surface area, better distributing the force on the palm.
E
This is design A made more catered to arthritic individuals. Given prolonged gripping, skidding due to weakness in the arms or numbing, repetition and low dexterity being challenges most prominently faced by most arthritic individuals (Dr. Backman’s interview), this design does the following: increased surface area going outwards towards the fingertips reduces the need for gripping and force, the wrist extension provides more support, the sequeezable texture of polyurethane allows for more supported gripping and the rough/textured (criss-cross) surface of the print makes it less slippery and more prominently sensed in case of numbing sensations. This design also has finger slots which provide further support and grip, and paradoxically, leverages individuals with rheumatoid arthritis low dexterity in different joints by using wrist immobilization as a way to reduce pain in the carpal tunnel and discomfort from our user’s previous wrist paralysis. It also leverages the inability of people with rheumatoid arthritis to make a complete fist by factoring in extensive gripping as a risk factor and thus, keeping the hand in a neutral position across a larger surface area. The benefits of this design with respect to our user stand (Design A, round 2), with the added benefit that the material is polyurethane which is both more affordable and lightweight as suggested by Dr. Bumbulovic.
F
Pipette is placed in mesh that is held up by a plastic structure. This would allow for the user to experience less weight when using the pipette compared to when they hold it without an additional tool.
G
A silicone sleeve that can be pulled onto the pipette. It will have thicker and thinner silicone portions that are distributed asymmetrically so that the user may rotate the sleeve to the position that is mot comfortable. There will also be texture on the surface, to increase grip. There will also be a drawn design on the surface to increase the appeal of the tool. It also contains a wrist brace to increase stability of the pipette.
H
Silicone that has a band to attach to wrap around and attach to the pipette. The front facing portion of the tool would increase in thickness at an angle. The silicone would also wrap around the hook of the pipette.
Dr. Usprech corrected our way of orienting the requirements and evaluation criteria: the requirements are pass/fail and need to have distinct cut-offs where; the design either falls into a given requirement or it does not. Evaluation criterions are more descriptive versions of the requirements and they are what weights are associated with. We made the aforementioned changes to our Table 2 and Table 3, which was seen in the following iterations of the requirements and evaluation criteria. She also discussed that if we are moving forward with the CAD process, we should first create a prototype using simple material, like cardboard or clay. That would allow us to understand the 3D benefits and limitations to our design, without investing excessive time into the CAD before realizing the design doesn’t work.
Dr. Jenna Usprech
Co-principal Investigator, PhD, P. Eng, Associate Professor of Teaching, SBME, UBC
User Conversation
According to our readings of Jude Pollen, inclusive projects must involve the user in as much of the design process as possible ([1]). That is why we included our user in the review of our WDM, the screening of our round 2 of C-sketch designs, and the creation of the satisfaction.
We first read our user agreement to her and she granted her verbal consent with regards to assisting us with the addition that all recordings would be deleted after the completion of this project. It was key that at she was aware that she could stop the interview at any point for any reason. Then, we began to look at our requirements and ensured that our weights, priorities and remaining details of the WDMs based on our first interview were valid; she confirmed that they looked good and that our quantification method was sound. We then proceeded to show her our designs one-by-one (Round 2) and described how we envisioned each to address her needs. Based on our conversation, we learned that she enjoyed the idea of wrist immobilization stating that she knows it is best for her to have her wrist in a neutral position, but she would always bend it to a harmful angle (Round 2, Design A). She also enjoyed the increasing thickness of our add on which gradually reduces the amount of gripping and upon understanding that Design B could be sterilized with ethanol, she also approved that design. Lastly, contrary to what we had expected, we learned that turning the pipette knob does not add to her strain; as a result, we removed that from our list of requirements. After communicating her satisfaction with the designs, we moved into quantifying her level of satisfaction as each requirement changed, which we made into our satisfaction curves.
Our discussions about each requirement are summarized in the table below, we asked her questions that would allow us to later quantify the values, since we knew what we would need to measure to determine the values of different satisfactions, which was then sketched into different curves.
Another goal of this meeting was to see the overlap between our discussion with Dr. Backman about the needs of individuals’ with rheumatoid arthritis and those of our current user. Upon describing the elements we had incorporated into our design (eg. texture to improve grip), she described that her situation also resulted in episodes of numbing and reduced sensory input, which means texture would aid both in grip and improving sensory input. This suggestion by Dr. Backman both expands the benefits of our tool to others, and is directly useful for our users needs.
After this meeting, we had a confirmed set of requirements with which we could now begin making our designs. Based on our user’s description of how each design addressed her needs, we were able to make more detailed CADs on Onshape. It also helped us understand the overlap between arthritis and our users situation, and how the common needs of both MSK groups can be used to create a more inclusive design. As our next steps, we needed to create and print multiple designs.
User
User Interview #2
Decision Framework #4
Thee following table (Table 7) was created in collaboration with our user. We asked different questions that allowed us to determine quantifiable values that can be determined later, which are seen in the user description. The satisfaction curve justification describes the reasoning behind the curves that are seen below. The designs need to be within these limits or it will fail. The limits to each aspect of the evaluation criteria is shown using a discontinuity in the functions. The values were determined based on the user description.
Table 7: Evaluation Criteria
Evaluation Criteria
User Descriptions
Satisfaction Curve - Justification
1
Combination of pipette and add on must remain lighter then the lightest multichannel pipette
Closest to as light as possible is preferred with a balance of light and heavy to have sufficient grip. 100% would be a bit lighter than current use (multichannel pipet-lite which is 240 grams), 0 would be heavier then the one she can’t use (regular Rainin pipette which is approximately 450 kg). Regular Rainin pipette would be 50%, same weight as light pipette you are using is 90%, if it was half way between heavy and light it be 70%.
The user described the weight and her satisfaction having a direct relationship. A weight of 0 gives 100% satisfaction but is unrealistic, so a point discontinuity describes that the lightest pipette possible is most ideal.
2
Decreased grip strength needed compared to regular pipette.
Intensity of grip after 45 min of gripping heavy pipette would be 0%. Equivalent is 45 min of straight dilutions. 100% would be the first moment of using lightest pipette. 50% intensity of grip after 22.5 min heaviest pipette.
Our user described grip strength reduction to be directly proportional to her satisfaction. See user descriptions for other properties of the curve.
3
Option to use 2 different muscles groups/positions
0% being able to only use wrist 100% would be using shoulder and wrist,
This is a pass/fail function and hence, two points are used with no regression line. Either two muscles are being used or just one. Using only the wrist is 0% satisfaction as that is what she already does and it causes strain, so being able to switch between both would give 100% satisfaction.
4
Wrist shouldn’t overexert from the angle of 180 +- 20 degrees
only neutral would be 80% only angled towards pinkie is most comfortable, to choose where the wrist is most comfortable 100%. She is aware that it is best for the user to keep a neutral wrist, but she is most comfortable with slight bending of the wrist.
The less exertion on the wrist, the better it is. Satisfaction and wrist exertion are exponentially related; she prefers to exert her wrist but it is not ideal for her condition, so the slope gains steepness more gradually in representing her satisfaction.
Satisfaction Curves #1
The four satisfaction curves that are described in Table 8.
Screening #2
We then performed two different screens, one where we only looked at the function requirements (Table 8) , ie. does the tool interfere with the pipette’s function then the other only looked at the user requirements (Table 9), ie. does it actually help the user. We then combined both screens to examine which design passed both.
Table 8: Screening - Function Requirements
Design
Pass/Fail
Reasoning - Requirements
A
Fail
Volume can not be seen - covered by the add on.
B
Fail
volume size will be hidden, interferes with ejection
C
Fail
would limit the user’s range of motion
D
Pass
N/A
E
Pass
N/A
F
Fail
Affects range of motion
G
Fail
volume size will be hidden, interferes with ejection
H
Pass
N/A
Table 9: Screening - User Requirements
If failed function requirements, modifications that would allow the design to pass will be added to return function.
Design
Pass/Fail
Reasoning - Needs
Modification of design which would allow for pass
A
Pass
N/A
N/A
B
Fail
Doesn’t allow for the use of two different muscle groups
Include a wrist stabilizer, sleeve interferes with ejection
C
Fail
Doesn’t have the ability to engage two different muscle groups
Include an add-on that would leverage a second muscle to switch between
D
Fail
Does not provide any support that would help keep wrist in a neutral position.
Include a wrist stabilizer
E
Pass
N/A
N/A
F
Fail
Affects range of motion
N/A
G
Fail
Doesn’t have the ability to engage two different muscle groups, does not provide any support that would help keep wrist in a neutral position.
Include a wrist stabilizer, sleeve interferes with ejection
H
Fail
Doesn’t allow for the use of two different muscle groups
Include a wrist stabilizer
Table 10: Final Result of Screening
Design
Pass/Fail
Modification to Pass
A
Fail
show volume values
B
Fail
Include a wrist stabilizer
C
Fail
Include a wrist stabilizer that enables switching between muscles (avoid repetition)
D
Fail
Include a wrist stabilizer
E
Pass
N/A
F
Fail
N/A
G
Fail
Include a wrist stabilizer
H
Fail
Include a wrist stabilizer
Thus far, we decided to move forward with 3D designing Design E as it fully passed.
