Agilent Measurement Journal - Issue 3 - 2007 - (Page 19)

A The newest version of this technology — MAC Mode III from Agilent — employs lock-in ampliﬁers to determine the oscillation amplitude and phase response of the cantilever, resulting in superior force regulation and phase imaging. Furthermore, there is less system noise and the cantilever can be operated at much smaller amplitudes. Subsequently, sample damage is decreased, probe sharpness is preserved, and resolution is greatly improved. In addition to facilitating high-resolution AFM imaging of delicate samples in ﬂuid, this oscillating probe technology permits singlepass imaging concurrent with Kelvin force microscopy and electric force microscopy to acquire simultaneous, highaccuracy topography and surface potential measurements. Higher resonance frequencies of the AFM cantilever can be utilized to provide contrast beyond that seen with fundamental amplitude and phase signals, allowing researchers to collect additional information about mechanical properties of the sample surface. Atomic force microscopy (AFM) has revolutionized the ﬁeld of interfacial surface science by enabling direct, high-resolution visualization of surface morphology in various solutions and gas environments. As new technologies simplify the preparation and handling of diverse sample types, the use of a powerful class of in situ AFM techniques is becoming increasingly prevalent in biological research. AFM works by bringing a cantilever tip into contact with the surface to be imaged. An ionic repulsive force from the surface applied to the tip bends the cantilever upward. The amount of bending, measured by a laser spot reﬂected onto a split photodetector, can be used to calculate the force. By keeping the force constant while scanning the tip across the surface, the vertical movement of the tip will follow the surface proﬁle and be recorded as surface topography. Heating or cooling the sample The addition of temperature control greatly enhances in situ AFM research. Physiological processes can be accelerated or decelerated, structures of many biological molecules can be altered, and biomolecular binding events can be controlled by heating or cooling. Agilent temperature controllers thermally isolate the sample plate from the rest of the AFM system and insulate the surrounding apparatus from the effects of heating or cooling. Advanced temperature controllers also provide a rapid settling time, thereby allowing the sample plate to reach temperature quickly and hold constant temperature for long periods of time. Agilent sample plates offer built-in temperature control, excellent thermal stability (±0.1° C or better), and the ability to heat, cool and precisely maintain extreme temperatures (from –30° C to +250° C) during AFM imaging. Imaging in liquid Manufacturers of AFM instrumentation have introduced several technologies designed speciﬁcally for in situ applications. Especially important are those techniques that enable AFM imaging of biological samples in water, physiologically relevant solutions, and buffers. One such development is the advent of an intermittent-contact AFM imaging mode that utilizes an AC magnetic ﬁeld to drive the atomic force microscope’s cantilever into oscillation. The precision control afforded by this magnetic AC (MAC) technique enables gentle, artifact-free measurement of samples in ﬂuid or air. Agilent Measurement Journal 19

Table of Contents Feed for the Digital Edition of Agilent Measurement Journal - Issue 3 - 2007

Applying Ingenuity to the Measurement of Emerging Technologies Contents Emerging Innovations Department Delivering Bigger Benefits by Optimizing Customer Workflows Measuring Material Properties at the Nanoscale Utilizing In Situ Atomic Force Microscopy in Life Science, Pharmaceutical and other Bio-Related Applications WiMAX™: Plotting a New Path to Global Mobility Addressing the Triple Complexity of Triple-Play Networks What Next for Mobile Telephony? Exploring the Inner Workings of Tire-Pressure Monitoring Systems Developing, Assessing and Applying a High-Resolution Thin-Film Magnetic Probe Making Accurate Settling-Time Measurements Using a Vector Network Analyzer Applying Metabolomics Methods to the Study of Bacterial Leaf Blight in Rice Plants Measuring Stream Dynamics with Fiber Optics survey

Agilent Measurement Journal - Issue 3 - 2007

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