High-speed atomic force microscopy (AFM) is important for following processes that occur on sub-second timescales for studies both in biology and materials science, and also for the ability to examine large areas of a specimen at high resolution in a practical length of time. Further developments of the previously reported high-speed contact-mode AFM are described. Two instruments are presented: (i) a high-speed flexure stage arrangement capable of imaging at a video rate of 30 fps, and (ii) an ultra-high speed instrument using a combined tuning fork and flexure-stage scanning system capable of ultra-high-speed imaging in excess of 1000 fps. Results of imaging collagen fibres under ambient conditions at rates of up to 1300 frames s −1 are presented. Despite tip-specimen relative velocities of up to 200 mm s −1 , no significant damage to the collagen specimen was observed even after tens of thousands of frames were acquired in the same area of the specimen.

Further developments of the previously reported high-speed contact-mode AFM are described. The technique is applied to the imaging of human chromosomes at video rate both in air and in water. These are the largest structures to have been imaged with high-speed AFM and the first imaging in liquid to be reported. A possible mechanism that allows such high-speed contact-mode imaging without significant damage to the sample is discussed in the context of the velocity dependence of the measured lateral force on the AFM tip.

Detection techniques currently used in scanning force microscopy impose limitations on the geometrical dimensions of the probes and, as a consequence, on their force sensitivity and temporal response. A new technique, based on scattered evanescent electromagnetic waves (SEW), is presented here that can detect the displacement of the extreme end of a vertically mounted cantilever. The resolution of this method is tested using different cantilever sizes and a theoretical model is developed to maximize the detection sensitivity. The applications presented here clearly show that the SEW detection system enables the use of force sensors with sub-micron size, opening new possibilities in the investigation of biomolecular systems and high speed imaging. Two types of cantilevers were successfully tested: a high force sensitivity lever with a spring constant of 0.17 pN nm(-1) and a resonant frequency of 32 kHz; and a high speed lever with a spring constant of 50 pN nm(-1) and a resonant frequency of 1.8 MHz. Both these force sensors were fabricated by modifying commercial microcantilevers in a focused ion beam system. It is important to emphasize that these modified cantilevers could not be detected by the conventional optical detection system used in commercial atomic force microscopes.

We report the implementation of a multitouch console for control of a holographic optical tweezers system. This innovative interface enables the independent but simultaneous interactive control of numerous optical traps by multiple users, overcoming the limitations of traditional interfaces and placing the full power of holographic optical tweezing into the operators' hands.

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Hydrogel-supported neural cell cultures are more in vivo-relevant compared to monolayers formed on glass or plastic substrates. However, there is a lack of synthetic microenvironment available for obtaining standardized and easily reproducible cultures characterized by tissue-mimicking cell composition, cell–cell interactions, and functional networks. Synthetic peptides representing the biological properties of the extracellular matrix (ECM) proteins have been reported to promote the adhesion-driven differentiation and functional maturation of neural cells. Thus, such peptides can serve as building blocks for engineering a standardized, all-synthetic environment. In this study, we have compared the effect of two chemically crosslinked hydrogel compositions on primary cerebellar cells: collagen-like peptide (CLP), and CLP with an integrin-binding motif arginine-glycine-aspartate (CLP-RGD), both conjugated to polyethylene glycol molecular templates (PEG-CLP and PEG-CLP-RGD, respectively) and fabricated as self-supporting membranes. Both compositions promoted a spontaneous organization of primary cerebellar cells into tissue-like clusters with fast-rising Ca2+ signals in soma, reflecting action potential generation. Notably, neurons on PEG-CLP-RGD had more neurites and better synaptic efficiency compared to PEG-CLP. For comparison, poly-L-lysine-coated glass and plastic surfaces did not induce formation of such spontaneously active networks. Additionally, contrary to the hydrogel membranes, glass substrates functionalized with PEG-CLP and PEG-CLP-RGD did not sufficiently support cell attachment and, subsequently, did not promote functional cluster formation. These results indicate that not only chemical composition but also the hydrogel structure and viscoelasticity are essential for bioactive signaling. The synthetic strategy based on ECM-mimicking, multifunctional blocks in registry with chemical crosslinking for obtaining tissue-like mechanical properties is promising for the development of fast and well standardized functional in vitro neural models and new regenerative therapies.

By monitoring the thermal noise of a vertically oriented micromechanical force sensor, we detect the viscoelastic response to shear for water in a subnanometer confinement. Measurements in pure water as well as under acidic and high-ionic-strength conditions relate this response to the effect of surface-adsorbed cations, which, because of their hydration, act as pinning centers restricting the mobility of the confined water molecules.

The mechanical characterization of biomolecular motors requires force sensors with sub-piconewton resolution. The coupling of a nanoscale motor to this type of microscale sensors introduces structural deformations in the motor according to the thermally activated degrees of freedom of the sensor. At present, no simple solution is available to reduce these effects. Here, we exploit the advantages of micro-fabricated cantilevers to produce a force sensor with essentially one degree of freedom and a spring constant of 0.03 pN nm(-1) for the study of the molecular motor protein kinesin-1. During processive runs, the cantilever constrains the movement of the cargo binding domain of kinesin in a straight line, parallel to the microtubule track, and excludes specific reaction coordinates such as cargo rotation. In these conditions, we measured a step size of 8.0 ± 0.4 nm and a maximal unloaded velocity of 820 ± 80 nm s(-1) at saturated adenosine triphosphate (ATP) concentration. We concluded that the motor does not need to rotate its tail as it moves through consecutive stepping cycles.