Visual force sensing with flexible nanowire buckling springs

Mechanical characterization of nanofibers using a nanomanipulator and atomic force microscope cantilever in a scanning electron microscope

Recently, we have developed an algorithm to quantitatively evaluate the roughness of spherical microparticles using scanning electron microscopy (SEM) images. The algorithm calculates the root-mean-squared profile roughness (RMS-RQ) of a single particle by analyzing the particle’s boundary. The information extracted from a single SEM image yields however only two-dimensional (2D) profile roughness data from the horizontal plane of a particle. The present study offers a practical procedure and the necessary software tools to gain quasi three-dimensional (3D) information from 2D particle contours recorded at different particle inclinations by tilting the sample (stage). This new approach was tested on a set of polystyrene core-iron oxide shell-silica shell particles as few micrometer-sized beads with different (tailored) surface roughness, providing the proof of principle that validates the applicability of the proposed method. SEM images of these particles were analyzed by the latest version of the developed algorithm, which allows to determine the analysis of particles in terms of roughness both within a batch and across the batches as a routine quality control procedure. A separate set of particles has been analyzed by atomic force microscopy (AFM) as a powerful complementary surface analysis technique integrated into SEM, and the roughness results have been compared.

This paper reports a thermal sensor assembled by two multi-walled carbon nanotubes (MWCNTs) inside a field emission scanning electron microscope (FESEM) which constructed a probe tip in order to detect the local environment of single cell. An atomic force microscope (AFM) cantilever was used for substrate which is composed by Si3N4, and double side was covered by gold layer. Two MWCNTs were assembled to both side of AFM cantilever individually by employing a nanorobotic manipulation. Then another AFM cantilever was used as an end effector to manipulate the MWCNTs to touch, and used electron beam induced deposition (EBID) to bonding the two MWCNTs. The MWCNTs probe thermal sensor was evaluation inside a thermostated container for 30°C to 60°C. The experimental results show the positive characteristics of the temperature coefficient of resistance (TCR). We hope this result will be used rapidly in future. © 2012 IEEE.

Calibration of AFM cantilever stiffness: a microfabricated array of reflective springs

This paper explores strategies for fabricating and maintaining a sharp atomic force microscope (AFM) tip suitable for AFM data storage applications. To this end, AFM cantilevers have been incorporated into micromachined sled carriers and air-bearing sliders. These supports act to limit the maximum loading force on the AFM tip and allow for improved vibration immunity for the AFM cantilever in comparison to macroscopic loading schemes. Readback from a patterned rotating disk has been demonstrated using these devices. Silicon-carbide AFM cantilevers with diamond tips have been fabricated in a process compatible with that of the sleds and sliders. Molded silicon-nitride tips defined by the intersection of three surfaces have also been fabricated for AFM cantilevers. The molds for plane-plane-concave tips are defined by two silicon {111} planes and a silicon-dioxide curved surface. By geometry, the three surfaces necessarily have a unique intersection point, which may improve the consistency in sharpness of these tips relative to conventional pyramidal tips.

Liver sinusoidal endothelial cells (LEC) contain fenestrae, which control the exchange of fluids, solutes, and particles between the sinusoidal blood and the microvillous surface of the parenchymal cells. The surface of LEC can be imaged by scanning electron microscopy (SEM) and atomic force microscopy (AFM). SEM and AFM images of LEC can be used to study dynamic changes in fenestrae by comparing specimens fixed after different experimental treatments. In this article, we report the different results obtained when contact (using a constant force) or noncontact (amplitude detection) imaging on the same cells was applied. Special attention was paid on the optimalization of the image acquisition of fenestrae, because quality SEM examinations of fenestrae have already extensively been described. The following advances and conclusions are presented here: 1) High-resolution imaging of slightly fixed LEC in fluid can be performed in noncontact AFM; 2) correct acquisition of images of fenestrae with regard to their size (Ø, ±200 nm) and shape (oval, without deformation) under liquid was possible with noncontact AFM, which was hitherto only feasible with fixed, dried, and coated LEC in contact AFM or SEM; 3) this mode of operation is more gentle to cells than contact mode; 4) images of LEC obtained in noncontact mode are of higher quality and are devoid of smearing artefacts, prominently present in contact-mode images; 5) it is of great importance to optimize feedback and scan parameters to obtain correct surface information; and 6) LEC isolated and cultured by our method are physiologically responsive and represent an ideal object for AFM studies, because the cells are thin, smooth, and well attached to the culture substrate and show dynamic fine structural details, such as fenestrae and coated pits, which cannot be seen by light microscopy. © 1997 John Wiley & Sons, Inc. Int J Imaging Syst Technol, 8, 162–167, 1997

At present, paper industry has a lot of problems in China, such as the shortage of forest resources and high cost of pulping. Paper industry must be seeking high yield and low cost pulping process. In order to reduce the cost of mechanical pulp and increase the use of mechanical pulp, a lot of research and patent showed that the refining energy consumption of mechanical pulp would be further decreased using the corresponding enzyme to modify fiber of the raw materials before refining. The effects of cellulases modification on masson pine mechanical pulp were investigated in this paper. The modification conditions were as follows: the dosage of enzyme 75IU/g (to bone dry materials), temperature 500C, time 150min, pH value 5.5 and pulp concentration 15%. The effects of cellulase modification on the surface and quality of masson pine fiber of mechanical pulp were investigated by scanning electron microscope (SEM), atomic force microscopy (AFM) and fiber quality analyzer (FQA). It was found from the images of SEM that the original fiber surface was smoothly but markedly corroded after the cellulase modification. Moreover, the modification brought about more external fibrillation and longitudinal tearing during refining. AFM measurement results showed that the fiber surface roughness was improved after the cellulase modification because that the middle lamella, primary wall and outer layer of secondary wall were broken. The results of FQA measurement showed that the average fiber length increased slightly.

Neural electrodes, as core components of brain-computer interfaces(BCIs), face critical challenges in achieving stable mechanical coupling with brain tissue to ensure high-quality signal acquisition. Current flexible electrodes, including semi-invasive meningeal-attached types and implantable cantilever designs, exhibit significant mechanical mismatches (elastic modulus 5-6 orders higher than brain tissue) due to material/structural limitations, leading to interfacial slippage. While thread-like implants (e.g., Neuralink's electrodes) improve compliance via elongated structures, quantitative characterization of mechano-bioelectric interactions remains unexplored. This study proposes a bioelectromechanical coupling strategy, emphasizing synchronized motion between the electrode and the brain tissue through exposed-end deformation. A 4-channel ultra-flexible electrode (40mm in length, 164µm in width, and 3µm in thickness) is optimized using finite-element simulations and zero relative-motion criteria, achieving an equivalent stiffness of 0.023 Nm-1-matching brain tissue micromotion stiffness. A nanorobotic manipulator installed inside a scanning electron microscope(SEM) with an atomic force microscope(AFM) cantilever enabled precision characterization under the simulated displacement of 25µm, revealing interfacial forces of 575 nN and piezoresistive sensitivities of 6.4 pAmm-1 (length) and 10.2 pAµm-1 (displacement). The dual-functionality (signal acquisition and micromotion sensing) electrodes demonstrate breakthrough potential, establishing quantitative design standards for next-generation bioelectronic implants.

Annealing effects in samples of silicon implanted with helium by plasma immersion ion implantation

SiC thin films (undoped and doped with SnO 2 at 1 at.%, 5 at.% and 10 at.% concentrations) are prepared using pulsed laser deposition on quartz substrates kept at room temperature. The XRD patterns show a crystalline cubic phase for the undoped and 10 at.% SnO 2 doped SiC thin films while 1 at.% and 5 at.% SnO 2 doped SiC thin films exhibit an amorphous nature. The formation of nanorods with a non-uniform distribution of nanoparticles are studied using various microscopic techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM). Non-uniform distribution of particles with an average diameter 50 nm is seen in SEM micrographs of undoped SiC. On doping with 10 at.% SnO 2 , nanorods of average length of 1 micron are formed which is evidenced from the SEM image. TEM images also supports the formation of nanorods of average diameter of 20 nm in the 10 at.% SnO 2 doped SiC thin films. TEM images also suggest the formation of nano particles of size ∼ 5 nm in 10 at.% SnO 2 doped SiC thin films. A low surface roughness of 3.6 and 1.69 nm is obtained for the undoped SiC and 10 at.% SnO 2 doped SiC thin films from the AFM analysis. The presence of Raman bands in the region 500– 600 cm−1 for all the samples indicates the disorder prevailing in the films. It is seen that with higher dopant concentrations, this band becomes more well-defined and appear with more intensities at higher wave numbers which suggests that SnO 2 doping increases disorder in the crystallites in the films. Optical band gaps of the films are estimated from the UV-Vis absorption spectra. Variation in band gap observed with doping concentration may be due to broadening of the absorption edge occurred by the impurity levels. A near interface trap induced blue photoluminescence is observed in the undoped, 5 at.% and 10 at.% SnO 2 doped SiC thin films. The open aperture Z-scan measurements revealed strong absorptive nonlinearities. The Z scan curves suggest that the films are good saturable absorbers with saturation intensity I s being 6 × 1012 and 5.9 × 1012 W/m2, respectively for the 1 at.% and 10 at.% SnO 2 doped SiC films.

Current methods to study atomic force microscope (AFM) cantilever dynamics use model simplification or are based on the non-trivial solution of the equation of motion. As an alternative method, transfer function analysis gives a more complete description of system dynamics. In this work a transfer function study of two different AFM configurations, the point force and base driven cantilever, is presented. Exact analytical expressions of the infinite dimensional transfer function are derived for cantilever deflection and slope along the cantilever. Frequency response and transfer function infinite product expansion are obtained for the case where system outputs are set at the free end of the cantilever. The frequency response reflects the full complexity of cantilever dynamics affected by the presence of an infinite number of poles and zeros. An analytical expression for all the zeros and poles of the system is obtained. From the frequency response and pole-zero investigations it is shown how cantilever actuation and output measurement affect AFM operation and cantilever dynamics modelling. Transfer function analysis of AFM cantilevers opens the possibility of model based AFM operation to increase imaging and manipulation performance.

The necessity for development of new drug delivery systems for poorly soluble drugs and therapeutics which targets directly the pathogenic area requires the design of complex systems in nanoscale. Atomic Force Microscopy (AFM) since its discovery offers a unique tool to develop novel drug delivery systems. Its capability to investigate, characterise surfaces and measure forces with spatial resolution at nano-scale respectively contributes to develop and analyse pharmaceutical systems and biomedical devices with complex structures and chemistries. Specifically, polymeric nanoparticles and liposomal drug formulation have been studied extensively by using AFM where their size and morphology where revealed [1]. However, apart from topographical information, AFM can provide details on the local compositions of the sample. There are many modes that can be used to achieve this but the most common is to monitor the phase shift of the oscillating cantilever in tapping mode Such ‘Phase imaging’ can be used to detect nanoscale variation in composition, adhesion, friction, viscoelasticity, and other properties of the materials. Changes in the phase lag often indicate changes in the properties of the sample surface. Phase imaging has proved an extremely useful tool for pharmaceutical characterization. Phase imaging has been used to reveal polymeric forms from single crystal measurements [2] to confirm phase separation of two copolymers for drug delivery [3], to establish the stability of the formulation on different environments [4] and to identify formation of amorphous domains during milling of crystalline salbutamol [5]. Moreover, the ability of AFM to operate on different conditions of temperature humidity and in liquid allows studying the kinetics of range of phenomena. An interesting work was published from Miyazaki et al. where the crystal growth rate of Nifedipine, dispersed in PEG polymer matrix, was quantified [6]. Also, the dissolution process of aspirin on different facets of the crystal was studied by Danesh et al . showing their differences in dissolution rate [7]. The ability of AFM to measure force measurements have been used to investigate interactions among the different compounds in the formulation. To achieve this, the AFM cantilever is modified by attaching a particle directly onto the probe tip and is brought in contact with the substrate of interest, the force required to separate them is the measure of their adhesion. This application of AFM has been used extensively to aerosol drug formulation where the API is associated with a carrier which is released in the site of actions. For instance, AFM has been used to investigate the adhesion force of salbutamol with different excipients [8]. Moreover, localised surface energy and young’s modulus of various compounds have been measured. For example, Young’s modulus were derived from both PLA and PLA/everolimus directly from stent surface on different temperatures. The results showed that everolimus does not affect the mechanical properties of PLA up to 1/1 (w/w) drug loading of the mixture. Also, a significant drop of the Young’s modulus in solution was observed at 36°C, suggests that in vivo the Tg of the polymer is below body temperature [9]. Furthermore, force measurements have been used to identify the encapsulation the efficiency of liposomes as the rigidity of encapsulating liposomes is higher [10].

Changes in properties of monolithic and conventional zirconia during aging process

Scanning electron microscopy (SEM) and ion beam milling (FIB) techniques are mature nanoscale measurement technologies, while Atomic Force Microscopy (AFM) is a developing technology with intense interest in the scientific community for basic research and development. We discuss the recent integration of these techniques into a single instrument enabled by technological innovation in AFM instrument design, and applications of this instrument for characterization of FIB milled trenches. An AFM integrated into the SEM/FIB has specific design constraints that need to be met involving the AFM scanner, probe design, and feedback loop so that it geometrically fits into the chamber without interfering with the electron and ion beams. An ultraflat scanning stage was thus developed for precise sample motion that enable large ranges (85 microns or greater) in x,y, z. SPM probes that do not interfere with the electron beam were manufactured from fused silica in a cantilevered geometry (see Fig 1) where there is full visualization of the tip, without any loss of SPM functionality. These probes are combined with a tuning fork based feedback mechanism to maintain accurate tip-sample control; this mechanism does not involve lasers or optical beam deflection that interferes with the electron and ion beams. The many benefits of this combined approach to three-dimensional nanoscale characterization are illustrated in the imaging of a FIB milled trench. Figure 2a shows an AFM image profiling a 25-µm-deep trench milled in silicon with FIB imaged with the large Z range of the system. In this measurement, the FIB beam was used to mill this feature, and it was followed immediately by AFM imaging without having to remove the specimen from the FIB chamber and search in the AFM. Furthermore, the true depth of the trench was measured by the AFM in a crosssectional profile (Figure 2b) while a 3D reconstruction revealed the geometry of the sidewall (Figure 2c). Sidewall imaging with such long and exposed tips now are feasible with this instrument. The red arrow in this image clearly shows a Pt decoration on this structure, and the white arrow shows an undercut. Additionally, the ability of AFM to quickly and easily follow FIB milling with high Z resolution provides a straightforward and convenient method to check on FIB milling results. This capability is demonstrated in Figure 3 where several FIB-milled features in Si were monitored during the milling process. The grayscale SEM image in Figure 3a can easily locate these features and measure their widths but cannot provide direct information on their depths. The AFM delivers a 3D reconstruction (Figure 3b), and a cross sectional profile that together provide a true topographic map of specimen features. These depth profiles demonstrate the linearity of the etching process with time. This instrument incorporates important innovations in the design and technology of atomic force microscopy enabling its integration with SEM and FIB into a single powerful capability.

Surface modifications play a significant role in the interaction and success of implants to adjacent tissues. This study evaluated the surface topography and in vitro cellular response of surface treatments on titanium performed by multiphase anodic spark deposition (ASD). The titanium surfaces examined were: BioSpark (BS) and OsseoSpark (OS), obtained by ASD method; BioRough™ (BR), a chemical etching treatment used for comparison; and commercially-pure grade-2 titanium (cpTi) used as a control. The samples were cut in discs (12 mm diameter; 0.5 mm thickness) and sterilised by λ-irradiation prior to use. All samples were imaged using Scanning Electron Microscopy (SEM) (Hitachi S-3500N, Hitachi High-Technologies) to characterise the surface in 2 dimensions. Atomic Force Microscopy (AFM) (Topometrix Explorer SPM, Veeco Metrology LLC, CA, USA) was performed in contact mode to investigate topography in 3 dimensions and qualitatively analyse the surface roughness. Physicochemical analysis was also performed using energy dispersive X-ray spectroscopy (EDS) (Oxford Instruments Microanalysis, UK). A human osteosarcoma cell line (HOS TE85) was used for in vitro analysis; MTT assay to determine cell metabolic activity and Alamar Blue™ (Serotec) for assessing cell proliferation. SEM images indicated that ASD treatment created a microrough surface with a web-like nanostructure. AFM images illustrated the 3-dimensional topographies and quantitatively analysed surface roughness by ranging from the roughest to the smoothest which were Br > OS > BS > cpTi, respectively. Cellular response results showed no toxic leachables released from the test samples, thus indicating all sample were biocompatible. A good level of cell proliferation compared to the control was observed indicating a favourable attachment surface. This study has indicated that the ASD treatment surface has a nanostructure topography favouring cell attachment and proliferation and can potentially be used to improve titanium performance by enhancing osseointegration for use in dental implantology.