Mechanical Properties of Human Skin

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Mechanical Properties of Human Skin

• An Introductory Survey of Instrumental
  Measurements
• Gary Lee Grove, Ph.D.
• cyberDERM, Inc.

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Skin Physiologist / Bioengineer

• Primary Research Interest
• Use of biomedical instruments
• to monitor changes in
• human skin structure function
• noninvasively

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Instruments that have been used to
non-invasively evaluate skin

• Ballistometer
  NMR
• Calipers pH meter
• Chromameter Photo- Acoustic Spectroscope
• Coefficient of Friction Photo-Mechanical
  Analyzer
• Cohesograph Photo- Plethysmograph
• Ellipsiometer Profilometer / Surfometer
• Evaporimeter Resonance Frequency Analyzer
• Extensiometer Rheometer
• Galvanic Skin Response Scratch Resistance Device
• Gas Bearing Electrodynamometer Sonic wave
  Propagation Device
• Identometer / Levelometer Sebumeter / Sebu-Tape
• IR Spectrometer Squametry Exfoliative
  Cytology
• Impedance meter Suction Cup Device
• Image Analysis Thermometers / Thermography
• Laser Doppler Velocimeter Twistometer / Dermal
  Torque Meter
• Load cells UltraSound A, B, C, M modes
• Nb. List is not all inclusive or up to date

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Three Pronged Approach for evaluating Skin Care
Product Performance

• Instrumental Measures
• Expert Graders Ratings Scores
• Panelists Self Assessments Perceptions

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Sometimes opinions do differ !
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More often there is concordance

• Typically, both groups use
• their visual tactile senses
• to assess changes in skin condition that are
  directly relevant to the problem.
• Meaningful Measures

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More often there is concordance

• Typically, both groups use
• their visual tactile senses
• to assess changes in skin condition that are
  directly relevant to the problem.
• Meaningful Measures

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Meaningful Measures

• Could be based on instrumental measurements that
  are related to
• Visual Changes
• Tactile Changes
• Physiological Changes
• Physical Changes
• should be objective reliable

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Meaningful Measures

• Could be based on instrumental measurements that
  are related to
• Visual Changes
• Tactile Changes
• Physiological Changes
• Physical Changes
• should be objective reliable

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Non Intrusive Methodsbased on Tactile Changes

• Does the skin feel
• soft, supple, firm, etc. ?

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Non Intrusive Methodsbased on Tactile Changes

• Whether the skin feels soft, supple, firm, etc.
  is an expression of
• Mechanical Properties
• Stress Strain
• Load Deformation
• many variations on this theme

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Skin Biomechanics Basic Strategy

• Load the skin in a standard fashion and measure
  the resulting Deformation

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Skin BiomechanicsVariations of Basic Strategy

• Loads can be
• heavy or light
• applied abruptly or progressively
• applied over large areas or small
• applied in different directions
• Deformation can occur in different ways
• push, pull, stretch, compress, twist, indent, etc.

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Non Intrusive Methodsbased on Tactile Changes

• Durometer (indents)
• Extensiometer (stretches)
• Dia-Stron MTT (stretches or compresses)
• Dia-Stron Dermal Torque Meter (twists)
• Gas Bearing Electrodynometer (wiggles)
• Dia-Stron Ballistometer ( impacts )
• DermaLab Suction Cup ( lifts )

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Non Intrusive Methodsbased on Tactile Changes

• Durometer (indents)
• Extensiometer (stretches)
• Dia-Stron MTT (stretches or compresses)
• Dia-Stron Dermal Torque Meter (twists)
• Gas Bearing Electrodynometer (wiggles)
• Dia-Stron Ballistometer ( impacts )
• DermaLab Suction Cup ( lifts )

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Non Intrusive Methodsbased on Tactile Changes

• Durometer (indents)
• Extensiometer (stretches)
• Dia-Stron MTT (stretches or compresses)
• Dia-Stron Dermal Torque Meter (twists)
• Gas Bearing Electrodynometer (wiggles)
• Dia-Stron Ballistometer ( impacts )
• DermaLab Suction Cup ( lifts )

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Durometer ... Hardness Testers

• Point indentation
• Spring loaded tip
• Read off dial indicator

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Durometer hardness
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Firmness Ratings

• Deflection or Compression Force

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Non Intrusive Methodsbased on Tactile Changes

• Durometer (indents)
• Extensiometer (stretches)
• Dia-Stron MTT (stretches or compresses)
• Dia-Stron Dermal Torque Meter (twists)
• Gas Bearing Electrodynometer (wiggles)
• Dia-Stron Ballistometer ( impacts )
• DermaLab Suction Cup ( lifts )

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Non Intrusive Methodsbased on Tactile Changes

• Durometer (indents)
• Extensiometer (stretches)
• Dia-Stron MTT (stretches or compresses)
• Dia-Stron Dermal Torque Meter (twists)
• Gas Bearing Electrodynometer (wiggles)
• Dia-Stron Ballistometer ( impacts )
• DermaLab Suction Cup ( lifts )

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DermaLab Suction Cup

CORTEX TECHNOLOGY DENMARK
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DermaLab ElasticitySuction cup principle
suction cup
skin
CORTEX TECHNOLOGY DENMARK
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DermaLab ElasticitySuction cup principle
suction chamber
suction cup
skin
CORTEX TECHNOLOGY DENMARK
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DermaLab ElasticitySuction cup principle
suction chamber
suction cup
elevation detectors
skin
CORTEX TECHNOLOGY DENMARK
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DermaLab ElasticitySuction cup principle
suction chamber
suction cup
to vacuum pump
elevation detectors
skin
CORTEX TECHNOLOGY DENMARK
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DermaLab ElasticitySuction cup principle
suction chamber
suction cup
to vacuum pump
elevation detectors
skin
CORTEX TECHNOLOGY DENMARK
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DermaLab ElasticitySuction cup principle
suction chamber
suction cup
to vacuum pump
elevation detectors
skin
CORTEX TECHNOLOGY DENMARK
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DermaLab ElasticitySuction cup principle
suction chamber
suction cup
to vacuum pump
elevation detectors
skin
CORTEX TECHNOLOGY DENMARK
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DermaLab ElasticitySuction cup principle
suction chamber
suction cup
to vacuum pump
elevation detectors
skin
CORTEX TECHNOLOGY DENMARK
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DermaLab ElasticitySuction cup principle
suction chamber
suction cup
to vacuum pump
elevation detectors
skin
CORTEX TECHNOLOGY DENMARK
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Hookes Law 1680

• if one power stretch or bend it one space, two
  will bend it two and three will bend it three,
• and so forth.
• as the force, so the extension

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Hookes Law for Elastic Materials

• stretch produced by
• simple tension is proportional to the load
• Stress / Strain
• Youngs Modulus
• E

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DermaLab Suction Cup Results
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Dermascan C Ver. 3High Resolution Ultrasound
CORTEX TECHNOLOGY DENMARK
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Speed of SoundEcho Technique

• Marin Mersene, 1640 316 m/s

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How far away is that thunderstorm ?

• Difference between seeing lighting and hearing
  thunder is approximately 5 seconds per mile

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Ultrasound Echography of SkinDermascan C ...
B-Mode

• similar to RADAR
• transducer moves
• collects A scans at known positions
• creates an array
• 2 D images BILT
• echo amplitude in pseudocolor display

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Ultrasound Echography of SkinDermascan C ...
B-Mode

• Normal Skin
• Poison Ivy
• Reaction

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M-Mode

• Same as A-Mode transducer remains fixed
• Stress the skin
• Trace major echoes over time
• Gives info on skin biomechanics

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Pulsed Echo Ultrasonography
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TeleMedicine

• DermaScan Images can easily be sent over the
  Internet

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