Penn State University Bioengineering

 Design and Development of a Calibration System to Secure a Target in a

Fluid-Filled Test Loop

Executive Summary | Design Overview | Alternative Designs | Final Design | Deliverables|  Budget

Sponsor:

Dr. Keefe B. Manning, Ph.D.
The Pennsylvania State University
Department of Bioengineering
University Park, PA 16802


Group Members:

Aaron Mishkin
Dimitrios Makrozahopoulos
Patrick Manganello
Christopher Woods
 

Executive Summary

Particle Image Velocimetry (PIV) is used to research the fluid mechanics of the cardiovascular system and is a leading technology in studying the fluid mechanics within cardiovascular prosthetics.  In vitro experiments using a circulation loop are conducted with particle image velocimetry.  By utilizing this technique, flow phenomena can be quantified and recorded to make improvements in cardiovascular prosthetics that in turn will aid in eliminating thrombus deposition and formation which are the main cause of malfunction in these types of devices.  PIV systems measure velocity by determining particle displacement over time using a double-pulsed laser technique. Other properties, such as mean velocity, turbulence intensity, and higher order flow statistics can also be obtained from this technology.  The PIV system uses two cameras that are positioned on the same exact point to superimpose the two profiles for a pseudo three dimensional analysis.  In order to calibrate this particular PIV system, the grid target must be held steady and rotate between each reference frame and translate the distance of the circulation loop.  A target that can be easily inserted and manipulated while inside these types of prosthetic devices is needed for calibration of the two cameras.   

Design Overview

Ø    1)  Insert and anchor a target into an in vitro cardiovascular circulation loop varying in diameter from 6-24 mm. 
Ø    2)  Multiple target dimensions must be securely attached to the calibration mechanism.
Ø    3)  Attach the target to a stable anchoring system.
Ø    4)  Control of target rotation and translation system. 
Ø    5)  The whole device must withstand contact with mineral oil and sodium iodide (NaI).
 

Alternative Designs

ØBalloon catheter anchoring mechanism
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Disadvantages

•Lack of stability-  A balloon anchor would need to have the compliance to navigate through the circulation loop and exert enough pressure to securely anchor the target. 
•Structural integrity- Only fluid under low pressure could be used to fill the balloon and may not form a strong anchor.  Pressure lines would add much bulk to the system.

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Advantages

•Simplistic design-  No moving parts on the balloon anchor and easily replaced.
•Well adapted to circulation loop-  The balloon potentially could anchor at any point inside the loop.

Final Design

Anchoring Mechanism

    Test tube brushes of three sizes were used to anchor the target inside various circulation loops
Translational Movement System

The rotational movement is controlled by a gear mechanism
Rotational Movement System

The translational movement is measured by a caliper that is set on the device

A piece of quarter inch polyethylene tubing concentrically encases a close-fitting piece of stainless steel braided wire that attaches to the calibration target downstream.  The 304 grade stainless steel has a diameter of 5/32” yielding a tight but still mobile system.  Both the translational and rotational system track very well without binding.  There is a notch in the tubing where the target attaches, allowing for 180° of precise rotation and approximately two inches of translation.  The system is anchored with interchangeable test tube cleaners downstream.  Set screws are adhered to the nylon brush in order to attach the tubing. A Mitutoyo economy electronic caliper from McMaster-Carr is attached to the stainless steel wire to make translation measurements in 0.1 mm and provide 0.2 mm of accuracy for measurements.  96 pitch precision spur gears were acquired from W.M. Berg®.  This gearing system is utilized for the mechanical system to satisfy the stipulated specification of 5º of rotation for the target on the mechanical system.

 

Deliverables

In order for the calibration to be considered a success, it must meet the following criteria:

1) Target must be inserted and anchored into a circulation loop of diameter one inch or less. 
SSolution: Test tubes brushes were specifically ordered to anchor inside tubes of 0.35 to 1 inch diameter (9 mm to 25.4 mm).

2) Target must lock in place for secure calibration. 

SSolution: Target attachment, anchors, and holders were developed for the specified target dimensions.     
 

3) Controlled translation for the target to satisfy +/- 1mm of accuracy.

ØSolution: The device incorporates a digital caliper from McMaster-Carr® of the required accuracy to measure the movement of the target.
 

4) Target specification needs to meet 5º of manual rotation for the target on the mechanical system

ØSolution: 96 pitch precision spur gears were acquired from W.M. Berg® for rotation measurements pertaining to the designed mechanical system.
 

5) Must withstand interaction with Mineral Oil and Sodium Iodine

ØSolution: All products were researched to determine the compatibility with the mineral oil and sodium iodine.  Polyethylene tubing was chosen as a material because it is very inert and compatible with a wide assortment of chemicals.  Verification of compatibility was done though a listing available through the Enpac Corporation.  Stainless steel braided cables of a 300 grade is extremely corrosion resistant and were purchased from McMaster-Carr®.  The test tube brush handles ordered are galvanized to resist corrosion or rust.
 

6) Target must be replaceable with other size targets. 

ØSolution: Target holders were manufactured according to the dimensions specified by the sponsor.

Budget

Product Company Size Quantity Cost
Test Tube Brush (Large) Fisher Scientific ®  1.5 (dia) x 4 in. 12 $14.30
Test Tube Brush (Medium) Fisher Scientific ®  3/4 (dia) x 3.5 in. 12 $19.95  
Test Tube Brush (Small) Fisher Scientific ®  1/2 (dia) x 3 in. 12 $15.60
Aluminum Raw materials, HDPE Raw material       $37.13
96 pitch precision spur gears W.M. Berg ®   2 $27.78
Mitutoyo economy electronic calipers McMaster-Carr ®   2 $82.30
Stainless Control Wire 300 Grade McMaster-Carr ® 5/32 (dia) x 36 in. 3 $32.30
Polyethylene tubing Lowes ® 1/4 (dia) in. x 6 feet 1 $4.28
Total       $213.68