Biomechanical Tissue Stimulator

Group 1:Matt Brady (BME/EE)Ankeet Choxi (BME)Misha Kotov (CS)Steven Manuel (ME)Adviser: Dr. V. Prasad Shastri

Overview

Design device that mimics physiological cyclic compressive loading to induce growth repair and remodeling mechanisms during tissue culture of articular cartilage

Past Work

•Ongoing cell-culture research project

•Prototype of stimulator has been constructed

•Many problems incurred

•Much research done for design of new device

•Range of force

•Sensors

•Detection and environment

What are we culturing and stimulating? Articular cartilage

covers human joint surfaces

transfers mechanical load to skeletal system

makes up ~2% of tissue volume in human body

Why stimulate culturing cartilage?

Hypothesized that mechanically stimulated cartilage will grow more like in vivo cartilage Increased formation of

cartilage matrix, stronger Type II collagen Glycosaminoglycan(GAG)

Persistent medical problems

Limited ability to self-repair avascular

Osteoarthrosis and related problems very common

100,000 AC injuries annually Arthritis 2nd most common US

disability $86 billion in medical expenses

annually 21% of adults in US diagnosed with

arthritis Very marketable project

Current Work

All parts have arrived Working towards implementation of sensors

and motor Constructing and attaching sensor mounts

to device frame Requires high level of precision mounting

Extending functionality of dummy application to control sensors and motor

Design Parameters

Accuracy of 20 microns Stimulation frequency of 1 Hz max Max load of 1 MPa or 100 N per sample 12 wells at once Max in-test stroke of 1 mm Total sample size of 10 mm 100 percent humidity at 98°F Use multiple waveforms for stimulation

Resolution and Accuracy

Driving Resolution: 4 microns Driving Accuracy: variable Measuring Resolution: 5 microns Measuring Accuracy: +/- 10 microns

Finite Element Analysis Completed finite element analysis and

finalized fabrication parameters

Contact Sensor

Made significant progress toward an easy to fabricate custom contact sensor

com

pute

r DAQ Card

Tissue Stimulator

Displacement Sensors

DriverPower Supply

Contact Sensors

Programming objectives

Program an application provide the following: Control the stepper motor Provide movement

feedback through displacement and force sensors

Gather relevant data

Application considerations

Precise motion control for the motor Display the baseline displacement where

contact is made with all wells; record measurements in reference to this point

Ideally, allow for customized routines, be able to save and repeat procedures

Record experiment figures in real time Provide exception handling routines Communication with the DAQ card

Current Work on Programming

Working to modify some pre-programmed modules to control stepper motor

Contacted our assigned application engineer from National Instruments

Set up the DAQ card and installed relevant software

Finished dummy application and working to extend its functionality

DAQ Card

Reads data from the motor and sensors

Keeps timing of device

Outputs the step and direction into the driver which runs the motor

Runs off LabView

Motor Driver

Driver takes inputs from the DAQ card and relays them to the motor

Allows fractional stepping of motor

Provides current limiting to keep motor from getting too hot and drawing too much power

Power Supply

Regulated 27V so motor runs at optimal current

Connects to driver, which in turn powers motor

Powers other components as well, however, resistors need to be used to lower voltage.

Displacement Sensor

Linear Encoder Will output

measurements of displacement

Needed to determine amount of strain applied to each tissue sample

Used as a tilt sensor (3 sensors)

Future Work

Attaching displacement sensors to device

Constructing contact sensors Programming data acquisition

protocols for sensors and motor Control program for motor

Begin phase testing with sensors and other components

Summary

Articular cartilage and problems

Biomechanical tissue stimulatorMechanically

stimulates cartilage Promotes growth of

tissue Design, considerations

Cost Breakdown

Frame: $210.00 Linear Actuator: $885.00 Contact Sensors: $10.00 Linear Encoder: $390.00 FlexiForce Sensors (4): $59.00 Strain Gages (5): $44.00 Power Supply: $35.00 Driver: $270.00 DAQ Cards (2): $600.00 Laptop: $560.00

Total: $3,063.00

End Goals

End Goal of Overall Project To develop implantable artificial

cartilage to replace damaged articular cartilage in the body.

End Goal of Senior Design Project To develop device that mimics

mechanical load placed on growing cartilage through controlled experimental stimulation.

References

Aufderheide, Adam C., Athanasiou, Kyriacos A. A Direct Compression Stimulator for Articular Cartilage and Meniscal Explants. (2006) Annals of Biomedical Engineering, Vol. 34. 1463-1474

Bobic,Vladimir. Current Status of the Articular Cartilage Repair biomed: The Journal of Regenerative Medicine Apr 2000, Vol. 1, No. 4: 37-41

Mansour JM. Biomechanics of Cartilage. (2004) Kinesiology: The Mechanics & Pathomechanics of Human Movement by Carol Oatis. 66-79.

Xia Y, Moody JB, Alhadlaq H. Orientational Dependence of T2 Relaxation in Articular Cartilage: a microscopic MRI study. (2002) Magnetic Resonance in Medicine 48: 460-469