Friction is a key component for real world applications. Any material that makes contact with another surface will have a friction force. Two key components of friction are the static and kinetic friction coefficients. These coefficients can be measured in a single pass over a sample surface with a specified contact part and a known load.

Typical Experimental Results:

Table 1 Friction Coefficient Results for Steel Plate against a Steel Ball

Test µs µk µkmax µkmin µkw
1 0.189 0.172 0.183 0.158 0.025
2 0.207 0.183 0.198 0.167 0.031
3 0.236 0.204 0.223 0.184 0.039
4 0.257 0.228 0.252 0.203 0.049
5 0.307 0.251 0.278 0.221 0.057
Average 0.239 0.208 0.227 0.187 0.04
S.D. 0.046 0.032 0.039 0.026 0.013

friction 3

Figure 3. Friction coefficient as a function of distance for a steel plate against a steel ball.

Friction Coefficient Results for Acuvue Oasys and Acuve TruEye Contact Lenses against a Glass Slide

Contact Lens µs µk µkmax µkmin µkw
Oaysis 0.255 0.197 0.213 0.181 0.032
TruEye 0.123 0.123 0.138 0.104 0.034

friction 4

Friction coefficient as a function of sliding distance for Acuvue Oasys with Hydraclear Plus contact lens against glass slide in saline contact lens solution.

friction 5

Friction coefficient as a function of sliding distance for the 1 Day Acuvue TruEye contact lens against glass slide in saline contact lens solution.

Applications:

Automated Stage Movement Ceramics Coatings and Films
Contact Lenses Fabrics Kinetic Friction
Metals Paper Peeling
PID Temperature Control Plastics Printed Surfaces
Printer Rollers Reciprocating Motion Repeat Measurements
Rubbing and Wear Testing Static Friction Surface Condition
Variable Cycles Variable Load Variable Speed
Various Contact Types Wear Resistance Wet and Dry Friction

 

For more information please read our application notes:
Friction of Contact Lenses in Saline Solution

 

Instruments: Kyowa TS-501 Triboster

triboster

Key Specifications:

Detecting Range 0-500gf (4.9N) Friction Force
Friction Coefficient Resolution 0.001
Maximum Sample Size 178x60x50mm
Measurement Speed 0.2-100mm/s
Maximum Repetitions 1000
Measurement Stroke 1-80mm
Maximum Temperature 200°C

 

Friction of Contact Lenses in Saline Solution

 

Friction is a measure of a surface’s resistance to motion. When two surfaces are rubbing against each other, friction acts as the force to prevent the two surfaces from moving in a given direction. Continued relative motion leads to material loss or wear of the surface and its friction counterpart. Over time, a surface will degrade to a point that renders the surface unusable for its designed application. Altering the surface chemistry can change the friction properties to better suit the application needs and help to prolong the material’s useful life.

 

AppNote-37

 

Figure 1. Friction coefficient as a function of sliding distance for the 1-Day Acuvue TruEye contact lens against glass slide in saline contact lens solution.

 

AppNote-38

 

Figure 2. Friction coefficient as a function of sliding distance for the Acuvue Oaysis with Hydraclear Plus contact lens against glass slide in saline contact lens solution.

 

The TS-501 Triboster, manufactured by Kyowa Interface Science Co., Ltd., is capable of measuring both the static and kinetic friction coefficients of a material surface in a single pass or multiple passes under dry or lubricated conditions with temperature control from room temperature to 180ºC. The high sensitivity friction transducer and low loads employed by the TS-501 allow for softer materials like polymers, fabrics and thin films to be tested with ease and accuracy. The velocity of the stage is automatically controlled by user input values from 0.02mm/s to 100mm/s.

 

AppNote-39

 

Most of the disposable contact lenses are made of extremely soft hydrogels with significant amount of water content. Wearing contact lenses is becoming trendy for people whether it is for cosmetic, corrective or therapeutic reasons. In addition to many designed functionalities of the contact lenses wearing comfort is a key factor to be well controlled by the contact lens designer. One of the aspects of the wearing comfort is the friction between eyelid and the contact lens.

 

As shown in Figures 1 and 2, and Table 1, two different kinds of commercially available contact lenses from Johnson & Johnson Vision Care, Inc. were tested for friction using the TS-501. The first kind of contact lens tested was 1-Day Acuvue TruEye disposable contact lens. The second kind of contact lens was Acuvue Oaysis Hydraclear Plus disposable contact lens. Both kinds of contact lenses were tested under the same conditions and parameters sliding against glass slide in saline contact lens solution. From the results it is obvious that the static and kinetic friction coefficients for the two kinds of contact lenses are different. The different friction coefficients would result in different wearing comfort for people.

 

ASTM Number Title Website Link
G115-10 Standard Guide for Measuring and Reporting Friction Coefficients Link
G163-10 Standard Guide for Digital Data Acquisition in Wear and Friction Measurements Link
D4103-90 Standard Practice for Preparation of Substrate Surfaces for Coefficient of Friction Testing Link
D2534-88 Standard Test Method for Coefficient of Kinetic Frictionfor Wax Coatings Link
G203-10 Standard Guide for Determining Friction Energy Dissipation in Reciprocating Tribosystems Link
D1894-14 Standard Test Method for Static and Kinetic Coefficients of Friction of Plastic Film and Sheeting Link

 

ISO Number Title Website Link
8295 Plastics– Film and sheeting– Determination of the coefficients of friction Link
20808 Fine ceramics (advanced ceramics, advanced technical ceramics)– Determination of friction and wear characteristics of monolithic ceramics by ball-on-disc method Link
15113 Rubber– Determination of frictional properties Link
15359 Paper and board– Determination of the static and kinetic coefficients of friction– Horizontal plane method Link