The Lab

The Dickinson nanomechanical research lab specialises in nanomechanical testing to measure the mechanical properties (hardness, modulus, stiffness, scratch resistance) of a wide range of materials broadly split into:

•  Site specific testing of microstructures
•  Realistic biological testing of soft and mineralised tissues
•  In-vivo, in-situ and in-vitro mechanical testing of biological specimens.
•  Thin films, coatings and tribological research
•  Nanostructures, nanowires/rods/particles
•  Microcompression of micro and nanoparticles
•  Hardness, modulus, scratch and wear resistance properties of materials.
•  Failure forensics, diagnostics and prevention research.

Our research is changing all the time based on new discoveries and advances in technology. To keep up with us real-time head over to our Facebook page.

Equipment

HYSITRON TI-950 TRIBOINDENTER

 

The Hysitron TI-950 TriboIndenter is equipped with quasistatic and dynamic indentation, lateral force for scratch measurements, SPM imaging, and a range of Berkovich, conical, cube corner and flat punch tips for both ambient and fluid testing.

This system is ideal for measuring the mechanical properties of very thin films (This is the only one of these machines available in New Zealand.)

MTS XP Nanoindenter

 

The MTS XP Nanoindenter is equipped with quasistatic and CSM indentation, lateral force for scratch measurements, nanovision, and a range of Berkovich and conical tips.

This system is ideal for measuring the mechanical properties of thicker films (This is the only one of these machines available in New Zealand.)

ActiveLife Scientific Biodent

 

The BioDent is a reference point indentation tester which measures the mechanical properties of biological tissues including bone and cartilage.  The system can measure both dry and under fluid conditions and is portable enough to be moved to your biological lab if you are in New Zealand.

Nanoindentation – The Process

Since the 1800’s when Friedrich Mohs introduced a simple scratch tester, the use of relative hardness as a way to characterize mechanical properties has evolved through Knoop, Vickers and Rockwell tests. These indentation tests have enabled the measurement of hardness of materials to become commonplace; however, the advancement of miniaturized devices and nanoscale films has necessitated mechanical property measurements at a much smaller scale. This led to the development of macro- and eventually nano-indenters and enable testing of a variety of materials including low-k-dielectrics, diamond-like-carbon coatings, composites, polymers and biomaterials. Nanoindentation and SPM imaging are inherently complimentary techniques providing valuable material information at the nanoscale and the TriboScope™ (Hysitron, Inc.) was the first commercial product to provide these techniques in combination.

Measuring at the nano and micro level provides a unique set of challenges; however nanoindentation has progressed to become a relatively simple technique suitable for many material types. Typically force, displacement and time are recorded simultaneously while a nanoindentation tip is pushed into the sample under a controlled load. The forces applied during nanoindentation can be as small as a few nanoNewtons or as large as several Newtons enabling a range of size scales to be studied. Nanoindentation tests are output as a load-displacement curve which can be analyzed using well defined equations to calculate the mechanical properties of the sample. The shape of the load-displacement curve can provide crucial information as to how the material responds showing ductility or brittleness, dislocation motion and creep behaviour. For more quantitative calculations, the stiffness can be deduced in many materials by measuring the slope of the tangent line at the initial point of unloading enabling hardness and modulus to be calculated. Due to the small volume sampled during nanoindentation, the test can be highly localized to a specific microstructural feature or within a thin film on a substrate.

In-situ SPM nanoindentation imaging is a technique which uses a piezo or closed loop scanner to raster scan the indenter tip across the sample surface while monitoring the force between the tip and the sample. The system is set to scan at a predefined constant force (similar to contact mode AFM), and any changes in this due to topography or surface roughness are monitored through the movement of the z-piezo and recorded. This force change as a function of position results in a map of the surface which can be carried out pre- and post-indentation enabling position control and confirmation that the tests were accurately placed. The advantages of using the same tip to image the surface and mechanically test the sample are plentiful, and include position accuracy, time saving, data location confirmation and local surface roughness measurements.

Our lab is passionate about sharing the knowledge around nanomechanical testing and you are most welcome to visit us (with a pre-arranged appointment) to watch the equipment in action and learn more about the technology that we use and techniques that we develop.  For real-time posts from the lab follow us on facebook where you can meet the team as well as see what we are researching.