156B Week 2
Overview of Status of Analysis, Design, Fabrication, Tests, etc.
Tests:
Conducted materials tests on silicone sheets
Conducted multiple tests, most thorough test done on 41X25 mm
Returned to original dimensions immediately after stress test conclusion
Determined the stress-strain curve for this silicone
Evaluated material elasticity, it can be strained to <5x original length without deformation.
Analysis:
Matlab model of vertical plunge vs. horizontal stretch was further validated, used to inform our design considerations
Matlab model was expanded to model plunger length optimization
Design:
Continued moving forward with motorizing manual design, switched to an inverted linear actuator design as our leading design.
Provided with a new staging/lens geometry, Jordan observed this new scope on 4/9
Fabrication:
Will begin assembly of 1-axis stretching over the weekend
Accomplishments from Previous Week
Accomplished stress-strain testing of silicone material
Met with sponsor, end-user, and end-user project team (4/10/13)
Displayed model and testing
Received feedback of our progress
Concerns include:
Further stressed focus and height issues
Membrane height change
Worried about possibility of negative transverse strain during stretch process
High-level discussion of percent-strain throughout the membrane
Dong mentioned Shu Chen's vascular stretching device
Equiaxial stretching device for vascular applications, could be use
Mikkie mentioned Y. C. Fong's tissue stretching
Done in 1971, not very applicable to this project
Explored various design possibilities, moving in the direction of current design
Inverted Hook design
Linear actuators with vertical orientation mounted outside of the petri dish
CAD and sketches made 4/10/13
Stepper Motors
Horizontally mounted stepper motors with lead screw and plunger attached
Sketches made 4/10/13
Goals for Next Week (list names after each item). Use specific and measurable objectives.
Assemble and begin evaluation of 1-axis stretch prototype with stepper and cam-arm (Anthony and Ben start 4/12 and 4/13)
Determine the possibility of a 0-height change function is possible/likely
Continue to evaluate low-profile designs that reduce height to fit within wider array of microscopes
Current "Inverted hook design" is 2.347" at max height
Should try to reduce that to
Sponsor Comments from Last Meeting and Actions Taken to Address these Comments (indicate date of comments and if via email or in person)
Concerned with the focus issues, re-emphasized this need during our meeting today (4/3 and 4/10)
Determined that our risk reduction prototype will explore this issue
We will look into the Poisson's ratio for silicone sheets and compare it to the focal length tolerances of the microscope
We should have 1% resolution on the stretch, to allow for greater functionality and use in more experiments
This is our big wow factor, something that is generally desired but not truly required for basic use.
Instructor Comments from Last Meeting and Actions Taken to Address these Comments (indicate date of comments and if via email or in person)
Need to explore risk reduction of the focus issues (4/3)
Determined concept for risk reduction prototype
1-axis stretching using stepper motor and cam-arm
Assembly to begin this weekend
Make presentation to sponsor of various designs and motor combinations, ask for feedback
Held presentation and meeting with sponsor group on 4/10
Explored motor options, and determined class of actuators that would work best for our project
Linear actuators (Haydon) with 4-axis
Haydon is a stepper motor with built-in linear transmission, .02mm resolution
Comments from Other Students in the Class (indicate date of comments and if via email or in person)
N/A
Risks and Areas of Concern
Need to look into poisson's ratio of the sheets, they are very much concerned with the focal length issue
They believe that the transverse negative strain could potentially change the focal point enough to lose signal on the neuron.
Total vertical clearance of design.
Mikky is now looking for perhaps 1.5" total height for best versatility
Static friction between o-ring and silicone during stretching process
Resources or Information Required but not Available
Schedule
Describe upcoming milestone
Develop a prototype to test the axial stretching, and focal length change, if any.
Update Gantt chart.
Budget (list amount spent and amount remaining)
0$
Progress on Report and Webpage
Internal Pages weekly update.
Uploaded CAD of 1 design potability