Tissue Mechanics Laboratory
Department of Orthopaedic Surgery
Department of Biomedical Engineering, Biomedical Engineering Institute
Location:
- 7-102 Hasselmo Hall
Director: Professor Jack Lewis
- Department of Orthopaedic Surgery
- Phone: 612-626-5021
- Email: lewis001@umn.edu
Instruments available:
- MicroBionix/Tytron low force uniaxial test machine (MTS, Inc.)
- Planar Biaxial low force test machine (Instron, Inc.)
- NanoindenterXP nano and micro indentation and scratch instrument (MTS, Inc.)
- FlexerCell FX-4000C Compression Plus System for tissue loading in culture conditions (Flexcell Int., Inc.)
NanoIndenter XP Mechanical Properties
Microprobe System
Specialist:
Description:
Automated system for instrumented indentation of materials. System consists of a controlled indentation tip with force controlled vertical displacement. Force and displacement versus time are recorded during the indentation. The specimen is mounted on a precision controlled x-y stage for precise positioning of indents. For hard materials, standard output is hardness and elastic modulus. Can be used for soft tissues with custom data reduction algorithms. The system is under computer control using TestWorks 4 for the Nanoindenter, allowing great flexibility in design and operation of custom testing protocols. The system has a lateral force option for scratch testing, a continuous stiffness module for continuous stiffness monitoring, and a higher precision test head.
Reservation procedure:
Instrument reservation is done on Yahoo Calendar (http://www.calendar.yahoo.com) ID is ‘umn_nano’; password is ‘mtsnano’. Minimum signup time is 2 hours.
Equipment:
NanoIndenter XP microprobe hardware: consisting of indenter, positioning microscope, controlling hardware. Force resolution: 1 mN; Displacement resolution: Displacement range: 1.5 mm. A variety of tip geometries are available, including Berkovitch, cube corner, cone.
Lateral Force option:
allows measurement of force in X and Y lateral directions, simultaneous with vertical mode operation.
High Load option:
Extends operation of the XP up to 1 kg in vertical load.
Continuous stiffness option:
Applies a harmonic oscillation on top of the quasi-static motion, allowing continuous monitoring of stiffness. Force amplitudes of 60 nN to 300 mN. Frequency range of 0.05 Hz to 200 Hz.
Dynamic Contact Module:
High resolution dynamic load indentation head. Force resolution: 1 nN; displacement resolution: < .002 nm. Displacement range: 15 um.
TestWorks 4 Explorer Level software:
Controls all components, records and analyzes data. Operates within Microsoft NT operating system. Explorer level allows extensive programming of test protocol. Data output exported to Excel files.
Applications:
Hard materials:
well developed methods for characterizing material properties of small material volumes
Elastic modulus and hardness of metals, ceramics, other hard materials. Viscoelastic properties of materials using harmonic loading (storage modulus, loss modulus), constant load (creep response), or constant displacement (relaxation response).
Scratch testing to determine film adhesion, coefficient of friction, variation of properties with depth.
Soft tissues:
Methods under development, but useable
Micropenetration to determine fracture toughness of soft tissues.
Scratch testing to determine fracture toughness of soft tissues.
Non-penetrating indentation to determine elastic and viscoelastic properties of soft tissues.
Specifications:
NanoIndenterXP:
- Indentation head assembly
- Displacement resolution <0.01 nm
- Total usable indenter travel 1.5 mm
- Maximum indentation depth > 500 um
- Load application Coil/magnet assembly
- Displacement measurement Capacitance gauge
- Max load 9.8 N
- Load resolution 50 nN
- Load frame stiffness 1 X 107 N/m
Motorized x-y sample manipulation table with computer mouse control. Positioning accuracy 1.5 um.
High performance vibration isolation system: air isolation table, passive environmental enclosure.
Optical imaging system with 4X and 40X lenses.
Fully automated, computerized data acquisition and control system including monitor and keyboard.
Computer:
Pentium III a450 MHz, 128 Mb RAM, 8.4 Gv Hard drive, 4X write/24X read CDRW, 3.5" 1.44 Mb floppy drive, ZIP drive
Complete operating and data analysis software package
- TestWorks 4 Professional level operation package
- TestWorks 4 Analyst data analysis package
- Microsoft Office 2000
Hewlett-Packard laser printer
CSM option (continuous stiffness module):
Continuous force oscillation, frequencies 0.05 to 200 Hz
Force amplitudes of 60 nN to 300 mN
Lateral force option:
X and Y lateral force measurement
Links
MTS, Inc.: http://www.mts.com/nano/nano_indenter_xp.htm
Biology EM Lab
IPRIME Characterization Facility
Specialist :
Dr. Narendra Simha (simha@umn.edu)
Description:
The Micro Bionix® Testing System is a highly accurate and convenient system for low-force static and dynamic mechanical testing of biomaterials and soft tissue.
Reservation procedure:
Instrument reservation is done on Yahoo Calander (http://www.calendar.yahoo.com) ID is ‘umn_mts’; password is ‘mtsmts’. Minimum signup time is 2 hours.
Equipment:
- MTS Micro Bionix Testing System
- Computer with Testworks II software
- Load cells of various ratings (50g, 5 N, 25 N)
- Vibration isolation table
- Grips
Applications:
Its dual static and dynamic capabilities make it ideal for a broad range of monotonic, durability, and fatigue testing. Tests can be run in load, displacement, and strain control modes. Displacement range is +/- 12 mm, making it ideal for testing compliant soft tissues. Soft tissue applications include cyclic or step loading to analyze viscoelastic responses, fracture mechanics, or fatigue.
Accessories:
Horizontally configured, the Micro Bionix system conveniently accommodates special accessories for tissue cultures and other soft specimens, including:
- Various load cells (50 g, 5 N, 250 N)
- Various grips (depending on application)
- Various accessories for different workbench configurations
- Adjustable-height mini-platform (typically used underneath specimen)
- Video camera, VCR, and monitor
- Video camera mount with 3-D adjustment
Specifications
The Micro Bionix system offers load test capability from 0.001 N to 250 N and a frequency of up to 50 Hz. It can test soft tissues with a 1-micrometer displacement resolution through 12-mm displacement range, making it ideal for tissue engineering applications. In addition, it plugs into a standard AC electrical outlet, eliminating the noise and inconvenience of oil-based hydraulic systems.
Sample Data
Relaxation curve for tissue strip grown in chondrocyte culture:
Tissue grown in chondrocyte culture undergoing a step displacement
followed by a ramp down to zero force. As the system constantly adjusts to
maintain zero force, the tissue beings to creep:
Operating Instructions
In order to properly operate the MTS MicroBionix Testing System in the most efficient manner, without damaging the equipment, hands-on training is required. Contact Brendan Koop at koop0022@umn.edu (primary contact) or Jack Lewis at lewis001@umn.edu to set up a training session.
Instrument:
Instron-Sacks Planar Biaxial Soft Tissue
Testing System
Specialist:
Dr. Narendra Simha (simha@umn.edu)
Description:
The low-force planar-biaxial system is designed to perform mechancal testing and property analysis of natural and bioartificial soft tissues. The test system allows single- and multi-axis tests to be performed in position, load control, or strain control and provides maximum flexibility for meeting various soft tissue testing needs.
Reservation procedures:
Equipment:
- Planar biaxial loading and control system: Four Instron electromechanical MicroTester actuators, two four-axis FastTrack 8800 digital controllers.
- Video-based strain control system: measures strain by tracking markers on specimen, controls based on this strain.
- Rapid imaging polarimeter: provides point wise polarization maps of loaded tissue
Applications:
- Planar mechanical testing
- Uniaxial, equibiaxial, non-uniform biaxial oading
- Determination of mechano-structural properties of soft tissues
- Dynamic characterization of viscoelastic properties
Multiple simultaneous uniaxial testing (up to 4 independent actuators; 2 functional independent uniaxial test stations)
Assessment of reorientation of fibers during mechanical loading
Accessories:
- Temperature controlled saline bath to ensure sample hydration
- Vibration isolation table
- Video camera, VCR, monitor
- Clamps with adjustable grip pressure
Specifications:
- Load cell capacity: +/- 250 g (+/- 2.45 N)
- Load cell accuracy +/- 0.5% of reading from 1-100% of full scale value
- Load cell resolution: +/- 6.25 mg
- Actuator stroke: 110 mm
- Actuator accuracy: +/- 0.1 micron
- Resolution: 0.050 micron
- Maximum ramp rate: 15.70 mm/sec
Instrument:
FlexerCell Compression/Tension Culture Loading
System
Specialist:
Prof. Narendra Simha (simha@umn.edu)
Description:
The FlexCell system provides a device to investigate the influence of mechanical force on cells and tissues in a culture environment. The system can subject a monolayer of cells to two-dimensional, equibiaxial strain, or bioartificial tissues to uniaxial tension or compression, up to approximately 15% strain. Cells/tissues can be exposed to static or cyclic loading with user-controlled waveforms.
Reservation procedures:
Equipment:
- FX-4000T Flexercell Tension System
- FX-4000C Flexercell Compression/FlexLink system (allows independent use of tension and compression systems)
Applications:
- Cyclic mechanical conditioning of bioartificial tissues
- Comparison of static vs. dynamic strain on cell behavior
Accessories:
- Various culture plates coated with specific extracellular matrix molecules (eg collagen, elastin)
- 37° humidified air incubator (CO2 capable).
- Vacuum and air sources.
- Biological hood
Specifications:
- Monolayer system requires cells to attach to silastic membrane.
- Tension system requires cells to be suspended in a biopolymer solution which upon gelation is connected to the device.
- Sterile technique is required throughout.