This review critically summarizes the recent advances of the microcantilever-based force sensors for atomic force microscope (AFM) applications. They are one the most common mechanical spring–mass systems and are extremely sensitive to changes in the resonant frequency, thus finding numerous applications especially for molecular sensing. Specifically, we comment on the latest progress in research on the deflection detection systems, fabrication, coating and functionalization of the microcantilevers and their application as bio- and chemical sensors. A trend on the recent breakthroughs on the study of biological samples using high-speed atomic force microscope is also reported in this review.

There has been an increasing interest for observing fast biological phenomena such as cell movements in circulations and action potentials. The laser scanning confocal microscopy offers a good spatial resolution and optical sectioning ability to observe various in vivo animal models. We developed a high speed laser scanning confocal microscope capable of acquiring 512 by 512 pixel images at 200 fps (frames per second). We have incorporated a fast rotating polygonal scanning mirror with 128 facets for the X-axis scanner. In order to increase the throughput of the Y-axis scanner, we applied a bi-directional scanning method for vertical scanning. This made it possible to scan along the Y-axis two times during each scanner motion cycle. For the image acquisition, we used a custom photomultiplier tube amplifier with a broad frequency band. In addition, custom imaging software was written for the new microscope. In order to verify the acquisition speed of the developed confocal microscope, a resolution target moving at a series of constant speeds and a sedated mouse with slight movements due to heartbeats were observed. By comparing successive frames, the frame acquisition speeds were calculated.

The thermal conductivity (k) of poly(acrylic acid) (PAA) nanofibers, which were electrospun at various electrospinning voltages, was measured using suspended microdevices. While the thermal conductivities of the as-spun PAA nanofibers varied depending on the electrospinning voltages, the most pronounced 3.1-fold increase in thermal conductivity in comparison to that of bulk PAA was observed at the electrospinning voltage of 14 kV. On the other hand, a reduction in the thermal conductivity of the nanofibers was observed when the as-spun nanofibers were either thermally annealed at the glass transition temperature of PAA or thermally crosslinked. It is notable that the thermal conductivity of crosslinked PAA nanofibers was comparable to that of crosslinked bulk PAA. Polarized Raman spectroscopy and Fourier transform infrared spectroscopy verified that the k enhancement via electrospinning and the k reduction by the thermal treatments could be attributed to the conformational changes between gauche and trans states, which may be further related to the orientation of molecular chains. In contrast, hydrogen bonds did not contribute significantly to the k enhancement. Additionally, the suppression of k observed for the crosslinked PAA nanofibers might result from the shortening of single molecular chains via crosslinking.

A high-speed atomic force microscope (HS-AFM) requires a specialized set of hardware and software and therefore improving video-rate HS-AFMs for general applications is an ongoing process. To improve the imaging rate of an AFM, all components have to be carefully redesigned since the slowest component determines the overall bandwidth of the instrument. In this work, we present a design of a compact HS-AFM scan-head featuring minimal loading on the Z-scanner. Using a custom-programmed controller and a high-speed lateral scanner, we demonstrate its working by obtaining topographic images of Blu-ray disk data tracks in contact- and tapping-modes. Images acquired using a contact-mode cantilever with a natural frequency of 60 kHz in constant deflection mode show good tracking of topography at 400 Hz. In constant height mode, tracking of topography is demonstrated at rates up to 1.9 kHz for the scan size of $1\mathsf{\mu }\mathrm{m}\times 1\mathsf{\mu }\mathrm{m}$ with $100\times 100$ pixels.