NDE of ceramic components manufactured by additive technologies
Additive Manufacturing (AM) adds in the first instance a new shaping method to the portfolio of established shaping methods of ceramics. New, unseen, shapes can be created directly from the computer model, potentially after numerical optimization (functional design). Sensory or actuator functions can be added by printing functional layers.
The additive shaping or process will not result in successful components without considering the technology chain from raw materials and preprocessing to post processing and testing. Non-destructive evaluation (NDE) shall be applied ideally already to prefinished components for optimizing process steps and reducing waste. Additive methods offer new challenges (e.g. internal stresses, imperfect interfaces between layers) and new opportunities for NDE methods.
These new opportunities are opened up by investigating thinner layers of materials directly in-operando of the AM shaping process. Ceramics structures, often difficult to investigate, will become better accessible.
Fraunhofer IKTS qualifies new optical methods for in-operando use during additive manufacturing. Recent examples of work will be presented.
We present our recent development concerning the evaluation of a low energy dose application to electron beam responding materials with a simple portable optical device. Electron beam irradiation is a promising option to sterilize sensitive and high performance products or surfaces at a low temperature and without moisture. Especially in the fields of the food industry and medicine, regulations regarding sterility are increasingly tightened. Because of this, a secure proof for electron-beam-assisted sterilization is required. However, no nondestructive and in situ method exists up until now. Our approach to provide a secure proof of sterilization is to place a suitable marker material based on rare-earth-doped phosphors inside or on the top of the packaging material of the respective product. Upon electron irradiation the marker material changes its luminescence properties as a function of the applied energy dose. We verified the energy dependence by means of time-resolved measurements of the luminescence decay of an upconversion phosphor with a portable optical device. In our experimental realization, short laser pulses in the near-infrared range are triggered by a microcontrol unit (MCU) and excite the marker material. The light emitted by the marker is collected in the range between 400 and 1100 nm via a silicon photodiode, processed by the MCU, and analyzed in a Labview program via a single-exponential fit. As a main result, we observe an increasing reduction of the luminescence lifetime with higher dose applications.
In this contribution we provide an overview of current investigations on optically active particles (nanodiamonds, upconversion phospors) for biohybrid and sensing applications. Due to their outstanding properties nanodiamonds gain attention in various application elds such as microelectronics, optical monitoring, medicine, and biotechnology. Beyond the typical diamond properties such as high thermal conductivity and extreme hardness, the carbon surface and its various functional groups enable diverse chemical and biological surface functionalization. At Fraunhofer IKTS-MD we develop a customization of material surfaces via integration of chemically modi ed nanodiamonds at variable surfaces, e.g bone implants and pipelines. For the rst purpose, nanodiamonds are covalently modi ed at their surface with amino or phosphate functionalities that are known to increase adhesion to bone or titanium alloys. The second type of surface is approached via mechanical implementation into coatings. Besides nanodiamonds, we also investigate the properties of upconversion phosphors. In our contribution we show how upconversion phosphors are used to verify sterilization processes via a change of optical properties due to sterilizing electron beam exposure.
We demonstrate the construction of an acoustic long period ber grating (LPG) incorporating an index tailored few-mode ber and discuss its implementation for high resolution microscopy and spectroscopy. The LPG is used to selectively excite radially or azimuthally polarized second-higher order modes. Among many others, possible applications are nano-particle characterization and optical near- eld microscopy. The goal is to increase the feasibility and reliability of nondestructive optical evaluation for micro- and nanoscale devices and nanostructured materials.
We present our recent investigations on time-resolved measurements of alterations in the temporal luminescence decay of upconversion phosphors induced by electron beam treatment. The latter is a promising alternative to low-temperature and dry sterilization of surfaces for sensitive packaging materials. Especially in the food and medical sector regulations concerning sterility are increasingly tightened. For this, a secure proof for electron-beam-assisted sterilization is required. However, no non-destructive and <i>in situ</i> method exists up to now. Our approach to provide a secure proof of sterilization is to place a suitable marker material based on rare-earth-doped phosphors inside or on top of the packaging material of the respective product. Upon electron irradiation the marker material changes its luminescent properties as a function of applied energy dose. We verified the energy dependence by means of time-resolved measurements of the luminescent decay of different upconversion materials. In our experimental realization short laser pulses in the near-infrared range excite the marker material. The emitted light is spectrally resolved in a monochromator, collected via a silicon photo diode, and analyzed with an oscilloscope. As the main results we observe a reduction of luminescence lifetime due to electron beam treatment dependent on the emission wavelength. Hence, the electron beam induces changes in the particles' up- and down-conversion properties from which the applied energy dose can be derived.
Secure proof of sterilization processes on packaging materials is an important issue in many economic sectors. In this
context, electron beam sterilization is a highly effective low temperature technique. However, verifying the application
of a sufficient electron dose is still difficult - especially on products with complex geometry. Here we report on an
optical, hence fast and contactless approach which gives reliable evidence of a successful e-beam treatment. The
technique is based on placing a suitable marker material (rare-earth based particles) inside or as a coating on the
packaging material. By electron irradiation these particles change their optical properties and thus indicate the successful
application of the electron beam.
We report on the biofunctionalization of nanodiamond surfaces in a two step procedure: chemical modification, resulting
in homogeneous and defined surface coating, with following addition of ssDNA. Carboxylation, thymidine coupling and
amination methods for chemical modification of diamond surfaces for further functionalization experiments were
applied. To enable the coupling process, biomolecules were also chemically modified with functional groups (-NH2).
FTIR spectroscopy, fluorescence microscopy and gel electrophoresis were applied for characterizing modified ND
particles and bioconjugates and for controlling the coupling success.
Goals: Improving cancer diagnosis is one of the important challenges at this time. The precise differentiation
between benign and malignant tissue is in the oncology and oncologic surgery of the utmost significance. A new
diagnostic system, that facilitates the decision which tissue has to be removed, would be appreciated. In previous
studies many attempts were made to use tissue fluorescence for cancer recognition. However, no clear correlation
was found between tissue type and fluorescence parameters like time and wavelength dependent fluorescence
intensity I(t, λ). The present study is focused on cooperative behaviour of cells in benign or malignant prostates
tissue reflecting differences in their metabolism.
Material and Methods: 50 prostate specimens were obtained directly after radical prostatectomy and from
each specimen 6 punch biopsies were taken. Time-resolved fluorescence spectra were recorded for 4 different
measurement points for each biopsy. The pathologist evaluated each measurement point separately. An algorithm
was developed to determine a relevant parameter of the time dependent fluorescence data (fractal dimension <i>D<sub>F</sub></i> ).
The results of the finding and the <i>D<sub>F</sub></i> -value were correlated for each point and then analysed with statistical
Results: A total of 1200 measurements points were analysed. The optimal algorithm and conditions for
discrimination between malignant and non-malignant tissue areas were found. The correct classification could
be stated in 93.4% of analysed points. The ROC-curve (AUC = 0.94) confirms the chosen statistical method as
well as it informs about the specificity (0.94) and sensitivity (0.90).
Conclusion: The new method seems to offer a very helpful diagnostic tool for pathologists as well as for
Various nanoparticles play a prominent role in modern biosciences and medicine. Especially fluorescent cellular
biomarkers are a prospective material for diagnostics and therapy. Nevertheless, most of the available biomarkers have
some drawbacks due to either physical and optical or cytotoxic properties. Here we investigated the potential of green
fluorescent nanodiamonds as extra- and intracellular biomarkers for living cells. We characterized the structure of the
used detonation synthesized nanodiamonds (DND) by X-ray diffraction (XRD) and the optical properties by
fluorescence and infrared spectroscopy.
For the extracellular attachment the nanodiamonds were functionalized by attaching antibodies that target extracellular
structures such as membrane. Transfections were mediated by dendrimers, cationic liposomes and protamine sulfate.
Using fluorescence microscopy, we confirmed successful extracellular binding on and transfection of the nanodiamonds
into prostate cancer cells. Furthermore, nanodiamonds can be targeted selectively to intracellular structures. Therefore,
nanodiamonds are a promising tool for biosensing.
In the present study, a smart coating for light metal alloys was developed and investigated. Chemically activated
nanodiamonds (CANDiT) were electrophoretically deposited onto anodized aluminum alloy AA2024 substrates in order
to increase corrosion resistance, enhance bonding properties and establish a means of corrosion monitoring based on the
fluorescence behavior of the particles. In order to create stable aqueous CANDiT dispersions suitable for electrophoretic
deposition, mechanical milling had to be implemented under specific chemical conditions. The influence of the CANDiT
volume fraction and pH of the dispersion on the electrochemical properties of the coated samples was investigated.
Linear voltammetry measurements reveal that the chemical characteristics of the CANDiT dispersion have a distinct
influence on the quality of the coating. The fluorescence spectra as well as fluorescence excitation spectra of the samples
show that corrosion can be easily detected by optical means. Furthermore, an optimization on the basis of "smart" -
algorithms for the data processing of a surface analysis by the
laser-speckle-method is presented.