Institute of Fundamental Technological Research

Using high resolution focused ion beam scanning electron microscopy (FIB-SEM) we study the details of cell-nanostructure interactions using serial block face imaging. 3T3 Fibroblast cellular monolayers are cultured on flat glass as a control surface and on two types of nanostructured scaffold substrates made from silicon black (Nanograss) with low- and high nanowire density. After culturing for 72 hours the cells were fixed, heavy metal stained, embedded in resin, and processed with FIB-SEM block face imaging without removing the substrate. The sample preparation procedure, image acquisition and image post-processing were specifically optimised for cellular monolayers cultured on nanostructured substrates. Cells display a wide range of interactions with the nanostructures depending on the surface morphology, but also greatly varying from one cell to another on the same substrate, illustrating a wide phenotypic variability. Depending on the substrate and cell, we observe that cells could for instance: break the nanowires and engulf them, flatten the nanowires or simply reside on top of them. Given the complexity of interactions, we have categorised our observations and created an overview map. The results demonstrate that detailed nanoscale resolution images are required to begin understanding the wide variety of individual cells’ interactions with a structured substrate. The map will provide a framework for light microscopy studies of such interactions indicating what modes of interactions must be considered.

Nanowires, Thin films, Glass, Scanning electron microscopy, Transmission electron microscopy, Cell membranes, Fibroblasts, Nanomaterials

We present here a proof of concept for a novel fabrication method of vertically aligned carbon nanotube forests, utilizing black silicon nanograss (a forest of silicon nanometer-sized spikes created with reactive ion etching) coated with titanium tungsten diffusion barrier as a template. The method allows maskless definition of carbon nanotube forests with control of their density, nanotube diameter and height. Four nanograss reactive ion etching recipes are investigated and their wafer-to-wafer repeatability, wafer uniformity, and density control is discussed. Evaluation of carbon nanotube forests grown on the nanograss substrates is presented with discussion of their morphology, diameter distribution, and catalyst thickness influence.

Carbon nanotubes, Black silicon, Nanograss, Maskless, Catalyst, Titanium tungsten

Engineered nanomaterials (ENMs) are increasingly being used in the food industry. In order to assess the efficacy and the risks of these materials, it is essential to have access to methods that not only detect the nanomaterials, but also provide information on the characteristics of the materials (e.g., size and shape).

This review presents an overview of electron microscopy (EM)-based methods that have been, or have the potential to be, applied to imaging ENMs in foodstuffs. We provide an overview of approaches to sample preparation, including drying, chemical treatment, fixation and cryogenic methods. We then describe standard and non-standard EM-based approaches that are available for imaging prepared samples. Finally, we present a strategy for selecting the most appropriate method for a particular foodstuff.

Cryo-electron microscopy, Detection, Environmental electron microscopy, Foodstuff, Imaging, Liquid electron microscopy, Nanoparticle, Sample preparation, Scanning electron microscopy (SEM), Transmission electron microscopy (TEM)

The movement of a micro cantilever was detected via a self constructed portable data acquisition prototype system which integrates a linear array of 32 1D amorphous silicon position sensitive detectors (PSD). The system was mounted on a microscope using a metal structure platform and the movement of the 30 µm wide by 400 µm long cantilever was tracked by analyzing the signals acquired by the 32 sensor array electronic readout system and the relevant data algorithm. The obtained results show a linear behavior of the photocurrent relating X and Y movement, with a non-linearity of about 3%, a spatial resolution of less than 2 µm along the lateral dimension of the sensor as well as of less than 3 µm along the perpendicular dimension of the sensor, when detecting just the micro-cantilever, and a spatial resolution of less than 1 µm when detecting the holding structure.

amorphous semiconductors, silicon, devices, systems

The purpose of the work was to examine the influence of topography and materials parameters on the value of pull-off force (adhesion) with future application of obtained results to solve the adhesion problem in microhandling. The research consists of two parts: theoretical and experimental. In theoretical research the model of contact, which takes into account the roughness of the contacted bodies is presented. In experimental part polymeric films with low surface energy were investigated as a solution to decrease adhesion at the gripping surface of the micromanipulator. To introduce surface roughness into the solution of polymers the nanoball structures (nanoparticles) were mixed. In result of these modifications three polymer samples were made: with density of nanoballs in the volume 2%, 5% and 10%. In result of these studies the dependences concerning the influence of the roughness on the adhesion were obtained.

Adhesion, Microgripper, Roughness, Polymer coatings

The position of a 40 μm wide by 400 μm long cantilever in a microscope was detected by a 32 lines array of 1D amorphous silicon position sensitive detectors (PSD). The sensor was placed in the ocular used for the CCD camera of a microscope and the alignment, focusing and positioning of the cantilever was achieved using the X–Y–Z translation table of the microscope that has a micrometer resolution controller. In this work we present results concerning the micro positioning of a cantilever and its holding structure through the reflected light that is detected by 1D/3D psd and converted to an analog signal proportional to the movement. The signal given by the 32 sensor array was analyzed directly without any electronic readout system or data algorithm. The obtained results show a linear behavior of the photovoltage relating X and Y movement, a non-linearity less than 2% and spatial resolution of 600 μV/μm.

Amorphous Semiconductors, Silicon, Devices

Polymeric films with low surface energy were investigated as a solution to decrease adhesion at the gripping surface of the micromanipulator. Eight polymeric films were investigated. The polymeric films were tested by an AFM (with standard silicon cantilever in normal environmental conditions) and by a triboscope under controlled conditions with varied substrate temperature. From this number of polymers, three of them: methylsilicone resin and methylphenylsilicone – all in aromatic hydrocarbon solution, were selected to coat the grippers due to their very low roughness (35–55 nm). One of samples was selected as an example of a polymer with a catalyst. The grippers were coated by dipping the working arms (single-crystal silicon) to the solution of polymer and then dried on the heater or in the environment conditions correspondingly. Several gripping experiments were performed to test the functionality of the coatings. Different objects – algae shells (∼250 μm) and silicon parts (5–100 μm) – were manipulated with uncoated and coated grippers. Influence of the polymer coating on the stiction effect was tested.

Adhesion, Microgripping, Polymer coatings

This work is focused on the design and the fabrication of an electrostatically driven microgripper for blood vessel manipulation. The goal is to realise a new system for the automated study of blood vessel wall contraction forces. Our device is based on an electrostatic comb-drive actuated silicon microgripper whose tips can be inserted into blood vessel samples providing isostatic conditions during the test and allowing contraction force measurement in the range of a few mN. A major innovation of the tool compared with existing devices is the capability of scaling down the diameter of the vessels that can be tested, reaching an internal diameter of 50 μm. In the paper a brief overview of the state of the art is presented, design details, simulations results and steps of the fabrication process are described.

Micromanipulation, Bio-MEMS, Microgripper, Comb drive actuators