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The Quest To Create Artificial Bone
The Quest To Create Artificial Bone
Background:
Background:
Researchers have extensively studied the naturally strong mechanical properties of bone in an attempt to replicate these properties in other materials to be used in the medical field and beyond. To do this, freeze casted samples are created to replicate the porous structure similar to that of bone, which can then be used for bioinspired, biomedical and structural applications, such as artificial bone implants. Before this, mechanical testing must first be carried out to fully understand the effects of bone’s complex structure. Specifically, 2mmx2mmx4mm samples of pig femur of 6 months old are cut on a diamond saw which then undergoes the freeze casting process. However, due to the slow nature of the sampling process, the variety of sizes and shapes of bone, and the mechanics of the diamond saw, this sampling process is needed for fixing and speeding up.
Objectives:
Our primary objectives are two fold:
Our primary objectives are two fold:
Design a jig and/or process to more accurately and efficiently prepare bone samples for mechanical testing than the current protocol. The design should allow for flexibility in sample size, but also create dimensionally consistent samples. Sample size will be at least 2x2x4 mm in size.
Design, prototype, and test a multi-compartment desiccator capable of holding multiple sets of delicate samples and keeping them dry in a low vacuum state. Desiccator should be stable and cost less than a commercial desiccator cabinet.
In regards to the first part of our objectives, the following video demonstrates the need for such a jig that makes the sampling process more efficient:
Final Design:
JIG + INSERTS
Our final design for the jig was to create a 4-step cutting process using 3 different types of jig inserts that were interchangeable with the current setup and a 4th sample holder that would be used for the polishing process of the bone. These different jig inserts were machined with stainless steel to provide the best grip on the samples without damaging the bone once clamped in. The following picture shows the 3 step diamond saw cutting processes using their respective jig inserts and the sample holder.
The "Two-Faced" jig insert have two sides that have horizontal and vertical crevasses that allow for more surface contact with the bone in its first initial stages. It grips the bone tightly enough to maintain parallel surfaces between cuts. After the first initial circular bone is cut, the "Pepe" insert can be used to grip the circular face of the sample tight enough to cut down to the longitudinal, radial, and transverse faces. After that, the "Skyscraper" jig insert can be used to hold onto those small 2mm faces of the sample without allowing them to move around or fall through the jig once clamped in.
Finally, after using these 3 different jig inserts to make the cuts using the diamond saw, the ~2x2x4mm sample can then be placed into our manufactured "Mr. T" sample holder for final polishing using the orbital sander. This holder allows these small samples to be sanded down all the way to the flat face of the holder to make those fine tuned adjustments to the samples cut from Stage 3.
FOURTH STAGE: MR T
FOURTH STAGE: MR T
DESICCATOR
DESICCATOR
The final design for the desiccator was to stick with the boxed acrylic design, but instead of making it 10”x10”x10” as originally planned, we made the walls thicker using ⅜” acrylic and made the overall dimension of the box 7.5”x7.5”x7.5” to allow for amore stable pressurized system. Acrylic was a cheap, easy to manufacture solution that will make it easy to replicate multiple compartments and replacements if need be.We used a completely removable door to allow for easier in and out access of the samples and less pressure leakage. 4 side clamps were added to create a more pressurized seal along with a gasket that runs along the inside of the door. The pressure gage and hose attachment were placed on the door to allow for easy access to the vacuum and easy readout for the researchers. Two trays with sliding panels on the side allow for 12 freeze casted samples to be taken in and out of the desiccator with ease. The trays have holds in them to allow ample amount of air flow between desiccant and samples.
Performance Results:
Jig Insert Panels + Polishing Holder - Implementing these jig insert panels along with the polishing holder decreased the sampling time by ~30%.
Desiccator - Building this square desiccator allowed for a permanent space in the lab designated for freeze casted samples to be dried out. These acrylic desiccators were able to hold 5psi for 24 hours.
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