Equipment

Atomic Force Microscopy – AFM 5500 (Agilent) Atomic Force Microscopy is able to give insights into structural changes on the surface. While such investigations usually are done in dry media, our equipment enables also an investigation of the samples in humid and wet conditions. This can be used to monitor the swelling behavior of polysaccharide samples e.g. cellulose films and fibers. The apparatus is placed in a box with a thermostat and therefore these investigations can be performed in a wide temperature range. This offers the possibility to study the influence of drying and wetting/drying processes (hornification) in real time under ambient atmosphere. For special applications (e.g. for printed circuits on paper) force measurements between the cellulose samples and the coated AFM tip can be a valuable information for the manufacturing and design of these papers. For flat surfaces layer thicknesses can be determined by scratching the surface. Suitable samples: fibers, pulps, films, model surfaces in dry, swollen and wet state.

Scanning Electron Microscopy with EDX – SUPRA 35 VP (Carl Zeiss) with Inca 400 (Oxford Instruments) Scanning Electron Microscopy is a complimentary technique for the investigation of the surface morphology. It can be used in combination with EDX detectors which are able to identify the elemental composition of the sample. This is extremely useful when coatings are applied to all types of cellulosic fibers. Impurities in the course of the coating procedures of cellulosic samples can be detected. Suitable samples: fibers, pulps, films, model surfaces in dry state.

Quartz Crystal Microbalance with Dissipation Unit (QCM-D) – E4 (QSense) QCM-D can be used for real-time monitoring of the adsorption/desorption behaviour at the solid-liquid interface. Any kind of substrates e.g. nanometric cellulose thin films (amorphous, crystalline, nano/microfibrillar cellulose) can be employed for this purpose. Swelling characteristics can be monitored and the water uptake and water content of the films can be determined by D2O/H2O exchange studies. Changes in the supramolecular structure (e.g. by heat treatment, chemical treatment, adsorption of biopolymers) are usually accompanied in a change in water content and uptake. Also the viscoelastic properties of the films can be investigated. Suitable samples: model surfaces in dry, swollen and wet state.

The SPR Navi 200 is a new generation surface plasmon resonance spectrometer. Unlike most SPR systems, SPR Navi™ 200 is a true goniometric SPR. This enables a wide angular scan range (¬= 40–78°) that produces a complete SPR curve with absolute angle information. The true goniometric SPR configuration confers great advantages as it widens the range of refractive indexes at which you can measure, allowing you to characterize surfaces in gas and/or liquid. It also allows you to check the quality of user-defined surfaces before sample injection, providing you with additional evidences. In our groups it is mostly used to determine the interaction capacity of biomolecules with surfaces.

Charge Titrations and Zeta Potential Determination – T70, DL53, DL28 (Mettler Toledo); ZetaOszi Titration techniques (pH-potentiometric, conductometric, and polyelectrolyte) are commonly used to determine the charging behaviour of various polyelectrolytes including charged polysaccharides in a solution or in a suspension (fibres, pulp, foils, membranes, etc.). They provide the information about: (1) the amount/charge density of dissociable polymer’s functional groups (acidic or basic), (2) the corresponding pK values, as well as (3) the point of zero charge/isoelectric point. All three titration techniques are often used in combination with each other in order to correlate the results and retrieve additional data about the surface behaviour of polymers. One can retrieve information about the adsorption/desorption of polymers to solid substrates (functionalisation of cellulosic materials), the surface functionality of polymers in solution and of solid substrates, and the influence of specific functional groups on the material’s bioactivity to mention the most important properties. As another complimentary technique we are using zeta potential determinations to validate the results from the titrations. Suitable samples: fibers, pulps, films in swollen and wet state. Model surfaces can be analyzed only with streaming potential analysis.  

Charge Titrations and Zeta Potential Determination – T70, DL53, DL28 (Mettler Toledo); ZetaOszi Titration techniques (pH-potentiometric, conductometric, and polyelectrolyte) are commonly used to determine the charging behaviour of various polyelectrolytes including charged polysaccharides in a solution or in a suspension (fibres, pulp, foils, membranes, etc.). They provide the information about: (1) the amount/charge density of dissociable polymer’s functional groups (acidic or basic), (2) the corresponding pK values, as well as (3) the point of zero charge/isoelectric point. All three titration techniques are often used in combination with each other in order to correlate the results and retrieve additional data about the surface behaviour of polymers. One can retrieve information about the adsorption/desorption of polymers to solid substrates (functionalisation of cellulosic materials), the surface functionality of polymers in solution and of solid substrates, and the influence of specific functional groups on the material’s bioactivity to mention the most important properties. As another complimentary technique we are using zeta potential determinations to validate the results from the titrations. Suitable samples: fibers, pulps, films in swollen and wet state. Model surfaces can be analyzed only with streaming potential analysis.   

Zetasizer Nano ZS and MPT-2 titrator:
The Zetasizer Nano ZS is a two angle particle and molecular size analyzer, used for detection of aggregates and measurement of small or dilute samples by dynamic light scattering with non-invasive backscatter optics. It also incorporates a zeta potential analyzer that uses electrophoretic light scattering for particles, molecules and surfaces, and a molecular weight analyzer using static light scattering. The Zetasizer Nano ZS is connected with the titration system MPT-2, providing automatic acid and base additions to the measured system when performing pH dependant size and zeta potential measurements.
  

Tensiometry – Tensiometer K12 (Krüss), OCA35 (Dataphysics) The wettability with water and other liquids (contact angle determination) is a routine method in our labs and a standard technique in nearly every experiment we perform. We have two goniometers which can determine the contact angle on flat surfaces. In addition, surface free energies can be calculated which gives information on the behaviour of the surface of interest with different liquids. This parameter is very important for the printing on cellulosic surfaces such as paper and cellophane films, but also to describe water and oil repellent properties. For fibrous samples, we employ tenziometer for evaluation of hydrophilic/hydrophobic character by determining contact angle and surface free energy of such samples. Tenziometer apparatus has also proved to be very useful in analysis of surface active agents, especially for quantification of critical micelle concentrations (in dependance of change in surface tension of water). Suitable samples: fibers, pulps, films, model surfaces in dry state.  

Capillary Zone Electrophoresis - Agilent Capillary Zone Electrophoresis (CZE) is relatively new separation technique and has been found highly useful in many fields including biopharmaceutical, forensics, clinical, etc. With this technique, materials that are soluble in aqueous/non aqueous medium including charged polymers and non charged molecules can be separated on the basis of differences in solute velocity in an applied electric field. We have long standing experience in the detection and quantification of monosaccharide components in technical galactoglucomannans (T-GGM) from spruce wood as well as from glucose content from the cellulosic degradation products. Suitable samples: solutions/dispersions of fibers, pulps, films.

UV-VIS spectrometry – Cary 60 UV-Vis (Agilent) Ultraviolet-visible spectroscopy or ultraviolet-visible spectrophotometry (UV-Vis or UV/Vis) refers to absorption spectroscopy in the ultraviolet-visible spectral region. This means it uses light in the visible and adjacent (near-UV and near-infrared (NIR)) ranges. The absorption in the visible range directly affects the perceived color of the chemicals involved. In this region of the electromagnetic spectrum, molecules undergo electronic transitions. UV/Vis spectroscopy is routinely used in the quantitative determination of solutions of transition metal ions highly conjugated organic compounds, and biological macromolecules.

Vibrational Spectroscopy (Infrared and Raman Spectroscopy) – Spectrum GX (Perkin Elmer) Infrared and Raman spectroscopy are valuable tools in the determination of the chemical composition due the characteristic absorption bands of functional groups in the IR area. Our labs are applying this technique on a routine basis for cellulose model films (ATR-IR) and bulk materials (fibers, pulps, cellophane films) The analysis comprises the identification of carboxy groups, amines, ketones, aldehydes as well as additives such as inorganic components. In some cases, it can be used for the determination of the degree of substitution of cellulose derivatives. Also the water content (1650 cm-1), can be estimated with this method. In addition, structural changes can be followed in the IR spectrum due to characteristic bands which determine the hydrogen bonding mode in the different cellulose cryst index, al structures. The ratio of certain bands can be used to determine crystallinity indexes (total crystallinity index, lateral order index, hydrogen bond index). In a similar manner, Raman can give additional information on the crystallinity of cellulose derivatives. We also have expertise on deuteration on cellulose to elucidate the fraction of mobile water in the samples. Suitable samples: fibers, pulps, films, model surfaces in dry and swollen state.

Sorption properties A variety of robust methods is available for determination of fibres’ ability to uptake and retain water, as well as moisture sorption degree. These standardised methods allow for fast evaluation of fibres’ interaction of water and aqueous-based treatment baths, especially from the point of view of technological processes. We perform determination of fibres’ swelling degree with the assistance of image analysis system, which consists of an optical microscope with a camera, connected to a computer. Fibre swelling is evaluated in situ, since microscope camera allows observation of fibres behaviour in a swelling solution. Image analysis software offers a wide range of computationall tools for determination of thickness, surface area, as well as pore volume in macro-scale on flat samples. For the model surfaces the QCM-D device can be used for water uptake studies and water content determination by using a D2O/H2O solvent exchange.

X-Ray Photoelectron spectroscopy and energy dispersive X-Ray diffraction X-Ray Photoelectron spectroscopy can be used to determine the elemental composition of cellulosic materials. Although this technique is working better for flat surfaces (e.g. model films) it can be done also on all types of pulps and fibers. This technique is not only revealing information about the elemental composition but also about the chemical environment of selected atoms which can be helpful in determining the amount of carboxylic groups on fibers for instance. When a coating is applied on cellulosic surface the amount of deposited material can be quantified. The oxidation states of elements can also be determined which is extremely important for the deposition of nanoparticles where very often a certain oxidation state is preferred. The equipment allows also a 3D mapping through etching using a UV laser. In a complimentary manner, EDX is employed usually in combination with electron microscopy techniques. By means of EDX, also the spatial element composition can be investigated e.g. the nanoparticle and its stabilizing shell which cannot be done with XPS. Suitable samples: fibers, pulps, films, model surfaces in dry state

Scanning Electron Microscopy with EDX – SUPRA 35 VP (Carl Zeiss) with Inca 400 (Oxford Instruments) Scanning Electron Microscopy is a complimentary technique for the investigation of the surface morphology. It can be used in combination with EDX detectors which are able to identify the elemental composition of the sample. This is extremely useful when coatings are applied to all types of cellulosic fibers. Impurities in the course of the coating procedures of cellulosic samples can be detected. Suitable samples: fibers, pulps, films, model surfaces in dry state.

Total organic carbon (TOC) – Multi N/C 2100 (Analytik Jena) Total organic carbon (TOC) content is an amount of carbon in an aqueous solution or suspension of organic matter; therefore it can be implemented as a quantitative indicator of the dissolved or suspended organic substances. TOC determination is based on the oxidation of organic carbon into carbon dioxide – analytical method is described in standard protocol SIST ISO 8245: 2000.

Vibrational Spectroscopy (Infrared and Raman Spectroscopy) – Spectrum GX (Perkin Elmer) Infrared and Raman spectroscopy are valuable tools in the determination of the chemical composition due the characteristic absorption bands of functional groups in the IR area. Our labs are applying this technique on a routine basis for cellulose model films (ATR-IR) and bulk materials (fibers, pulps, cellophane films) The analysis comprises the identification of carboxy groups, amines, ketones, aldehydes as well as additives such as inorganic components. In some cases, it can be used for the determination of the degree of substitution of cellulose derivatives. Also the water content (1650 cm-1), can be estimated with this method. In addition, structural changes can be followed in the IR spectrum due to characteristic bands which determine the hydrogen bonding mode in the different cellulose cryst index, al structures. The ratio of certain bands can be used to determine crystallinity indexes (total crystallinity index, lateral order index, hydrogen bond index). In a similar manner, Raman can give additional information on the crystallinity of cellulose derivatives. We also have expertise on deuteration on cellulose to elucidate the fraction of mobile water in the samples. Suitable samples: fibers, pulps, films, model surfaces in dry and swollen state.

Nozzle-less electrospinning device – Nanospider NS500 (Elmarco) and
Needle jet electrospinning device
Electrospinning is a spinning technique with a unique approach using electrostatic forces to produce fine fibres from polymer solutions or melts. Fibres produced by electrospinning have a thinner diameter (from nanometer to micrometer) and a large surface area than those obtained from conventional spinning processes. The technique allows addition of different nanoparticles (metal, ceramic, nanocapsules) or other additives (active substances, drugs, perfumes, proteins…) into the spinning solution. The solution is fed to the machine with the help of spinning electrodes (nozzle-less) or an injection (needle jet). Electrospinning process is conducted at room temperature with atmospheric conditions.

Fujifilm Dimatix DMP-2831 ink jet printer can be used with flat substrates and is capable of jetting a wide range of fluids. Variable jetting resolution and pattern creation is PC-controlled. It uses low cost, user-fillable piezo-based ink jet print cartridges.

MakerBot Replicator 2X Experimental 3D printer with dual extrusion is optimized for printing with MakerBot ABS and Dissolvable Filament with a 100-Micron Layer Resolution. Bioscaffolder is a unique 3D bio-printer, which allows simultaneous printing of cell scaffolds and live cells. It employs two technologies, pneumatic extrusion printing and piezoelectric ink jet printing. The piezoelectric dispensing system enables printing of live cells or matrix proteins embedded in or seeded on the scaffold material. The Bioscaffolder consist of multi-Z-drives, which can print different materials at various pressures and temperatures (for maximum flexibility). The 3D bio-printer allows printing of different biocompatible materials, which form hydrogels (e.g. CMC, alginate) and also other thermoplastic materials like PCL, bone cement paste, biocompatible silicones etc.

Spin-coating Spin coating is a procedure used to deposit uniform thin films to flat substrates. Usually a small amount of coating material is applied on the center of the substrate, which is then rotated at high speed in order to spread the coating material by centrifugal force. A machine used for spin coating is called a spin coater.

Freeze drying is a process of sublimation of frozen water from a sample under vacuum conditions. Two of the most important differences between freeze drying and other types of drying are: with freeze drying material solidifies before the actual drying and the removal of water from the material occurs with a process of sublimation, i.e. direct transition from ice into vapour. By freezing the sample we achieve a partial dehydration of the sample, its solidification and the shaping of the samples morphology. Its implementation retains the porous structure of materials, amongst other features, and is a convenient procedure for preparation of aerogels.