Hysitron PI 88 SEM PicoIndenter
Standard Testing Modes
Precise lateral positioning and nanoscale load and depth control allow for the quantitative determination of fundamental mechanical properties such as hardness and elastic modulus for a wide variety of materials.
Direct-pull and Push-to-Pull (PTP) testing of dog-bone specimens, thin films, or nanowires allows for the in-situ measurement of stress-strain behavior in low dimensional materials not easily tested by traditional means.
Accurate loading alignment and specimen size measurement using SEM imaging enables straightforward bending stiffness and fracture toughness measurements for single-phase, composite, or layered materials.
Pillars, particles, and other small scale structures can be compressed to measure stress-strain behavior and yield properties while observing deformation mechanisms in real time. Proper tip alignment is verified using SEM imaging.
Optional upgrade Modes
With most modern materials, it is not enough to simply measure mechanical properties at room temperature when the material is processed at, or put into service in non-ambient temperatures. To advance understanding of the mechanical behavior of materials at elevated temperatures or in harsh environments, Bruker has developed sample heating upgrade options designed specifically for the SEM and TEM Series PicoIndenter instruments.
Bruker offers two heating options for the PI Series instruments at temperatures up to 400°C and 800°C. In-situ heating up to 400°C is accomplished through the use of a resistive MEMS heater. This activates a variety of deformation mechanisms for nanomechanical study, such as the brittle-to-ductile transition in glasses and polymers. Due to the small size of the heating element, the region of elevated temperature is highly localized which minimizes extraneous heating of system components and provides the maximum level of stability for mechanical testing. Temperature is actively measured and feedback-controlled to ensure that the desired value is achieved.
For the PI 85L and PI 88 SEM PicoIndenter instruments, a newly developed heating option enables high resolution in-situ nanomechanical characterization of mechanical properties as a function of temperature. Such testing benefits applications (aerospace, automotive, nuclear, fusion, etc.) which demand high temperature materials capable of reliable performance in extreme operational environments. Featuring active tip heating and a liquid cooled heat sink, the system was designed to maximize the testing temperature, while minimizing drift and heat transfer to the microscope chamber.
Electrical Characterization Module (ECM) for the PI Series instruments provides a powerful solution for simultaneous in-situ electrical and mechanical measurements. Using a conductive path that connects the probe and sample, a voltage bias is applied to allow continuous measurement of evolving electrical contact conditions as a function of applied force and probe displacement. Site-specific testing can be performed by confirming proper tip placement with electron microscope imaging. Through-tip electrical measurements can also be used to gain insight into electromechanical properties of micro- or nano-structures such as pillars and particles. Humidity or water adsorption effects are minimized by the vacuum environment of the electron microscope.
Furthering the capabilities of ECM, a MEMS Electrical Push-to-Pull (E-PTP) device enables tensile testing while simultaneously measuring sample resistivity using a standard four-point measurement. The separation of current sourcing and voltage sensing electrodes allow accurate measurements of the electrical properties by elimination of contact and lead resistance on the measurement. Voltage sweeps can also be performed to measure IV curves, while true stress and strain are determined by monitoring and measuring specimen dimensions in the electron microscope.
Now that 1D and 2D materials can be rapidly and consistently synthesized, new mechanical characterization techniques are needed to evaluate and optimize their mechanical properties for use in the next generation of products and devices. To address the need to provide a suitable testing platform for these new forms of material, Bruker has developed the Push-to-Pull (PTP) device, which is an in-situ tensile apparatus designed to work in conjunction with the PI Series PicoIndenter instruments for SEM and TEM.
The PTP device is a consumable, MEMS-fabricated flexure device to which a nanotube or thin-film specimen can be mounted. Once prepared, the sample is transferred to the PicoIndenter system and a quantitative tensile load is applied. Mechanical data is used to calculate tensile properties while simultaneous electron microscope imaging provides real time video of the microstructure behavior. An electrical version of the device named the electrical Push-to-Pull (E-PTP) further expands the capabilities and enables four point electrical measurements throughout the tensile experiment.
Materials such as biological materials, glasses, polymers, and some metals exhibit significant time dependency with respect to mechanical properties. This viscoelasticity makes it difficult to completely describe the material response using traditional nanoindentation techniques. Building upon traditional dynamic mechanical analysis theory (DMA), Bruker has established its nanoDynamic Mode option for the in-situ mechanical analysis of nanoscale materials.
NanoDynamic Mode offers several testing modes in which an oscillating force is applied to a sample and the resultant displacement amplitude and phase shift are measured using a lock-in amplifier. Using this technique, the contact stiffness and damping properties of the material can be accurately determined, allowing for the measurement of storage (E’) and loss (E’’) moduli, as well as tan delta. Additionally, this technique has been expanded to include additional testing modes for characterizing creep and inducing fatigue in a wide variety of materials or structures while deformation is simultaneously monitored with the electron microscope.
Tribological measurements benefit directly from in-situ techniques which shed light on deformation processes occurring at the sliding interface. In addition to enabling direct observation of wear evolution, in-situ tribology can also be used for studies of friction, tribochemical reactions, interfacial adhesion, abrasion resistance, and nanoparticle rolling. The nanoScratch option for Bruker's Hysitron PI 95 TEM PicoIndenter® and Hysitron PI 88 SEM PicoIndenter® instruments enables high resolution measurements with simultaneous normal and lateral force sensing.
nanoScratch testing is accomplished by applying a normal load in a controlled fashion while measuring the lateral force between the probe and sample. By selecting the appropriate normal loading profile and lateral displacement pattern, many different types of tests can be performed. From the force and displacement data, useful information such as critical load, film adhesion, and delamination force can be measured. Reciprocating scratch tests can also be performed to study wear mechanisms over longer periods of time. This data provides a wealth of information concerning materials behavior under simultaneous normal and lateral stresses which is supplemented by direct observation electron microscope imaging.