48 research outputs found
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Ultrafast imaging Raman spectroscopy of large-area samples without stepwise scanning
Step-by-step, time-consuming scanning of the sample is still the state-of-the-art in imaging Raman spectroscopy. Even for a few 100 image points the measurement time may add up to minutes or hours. A radical decrease in measurement time can be achieved by applying multiplex spectrographs coupled to imaging fiber bundles that are successfully used in astronomy. For optimal use of the scarce and expensive observation time at astronomical observatories, special high-performance spectrograph systems were developed. They are designed for recording thousands of spatially resolved spectra of a two-dimensional image field within one single exposure. Transferring this technology to imaging Raman spectroscopy allows a considerably faster acquisition of chemical maps. Currently, an imaging field of up to 1 cm2 can be investigated. For porcine skin the required measurement time is less than 1 min. For this reason, this technique is of particular interest for medical diagnostics, e.g., the identification of potentially cancerous abnormalities of skin tissue
Wide Field Spectral Imaging with Shifted Excitation Raman Difference Spectroscopy Using the Nod and Shuffle Technique
Wide field Raman imaging using the integral field spectroscopy approach was
used as a fast, one shot imaging method for the simultaneous collection of all
spectra composing a Raman image. For the suppression of autofluorescence and
background signals such as room light, shifted excitation Raman difference
spectroscopy (SERDS) was applied to remove background artifacts in Raman
spectra. To reduce acquisition times in wide field SERDS imaging, we adapted
the nod and shuffle technique from astrophysics and implemented it into a wide
field SERDS imaging setup. In our adapted version, the nod corresponds to the
change in excitation wavelength, whereas the shuffle corresponds to the
shifting of charges up and down on a Charge-Coupled Device (CCD) chip
synchronous to the change in excitation wavelength. We coupled this improved
wide field SERDS imaging setup to diode lasers with 784.4/785.5 and 457.7/458.9
nm excitation and applied it to samples such as paracetamol and aspirin
tablets, polystyrene and polymethyl methacrylate beads, as well as pork meat
using multiple accumulations with acquisition times in the range of 50 to 200
ms. The results tackle two main challenges of SERDS imaging: gradual
photobleaching changes the autofluorescence background, and multiple readouts
of CCD detector prolong the acquisition time.Comment: Accepted and Published by "Sensors" Journal, 19 pages, 8 figure
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Wide Field Spectral Imaging with Shifted Excitation Raman Difference Spectroscopy Using the Nod and Shuffle Technique
Wide field Raman imaging using the integral field spectroscopy approach was used as a fast, one shot imaging method for the simultaneous collection of all spectra composing a Raman image. For the suppression of autofluorescence and background signals such as room light, shifted excitation Raman difference spectroscopy (SERDS) was applied to remove background artifacts in Raman spectra. To reduce acquisition times in wide field SERDS imaging, we adapted the nod and shuffle technique from astrophysics and implemented it into a wide field SERDS imaging setup. In our adapted version, the nod corresponds to the change in excitation wavelength, whereas the shuffle corresponds to the shifting of charges up and down on a Charge-Coupled Device (CCD) chip synchronous to the change in excitation wavelength. We coupled this improved wide field SERDS imaging setup to diode lasers with 784.4/785.5 and 457.7/458.9 nm excitation and applied it to samples such as paracetamol and aspirin tablets, polystyrene and polymethyl methacrylate beads, as well as pork meat using multiple accumulations with acquisition times in the range of 50 to 200 ms. The results tackle two main challenges of SERDS imaging: gradual photobleaching changes the autofluorescence background, and multiple readouts of CCD detector prolong the acquisition time
A dynamic multi-organ-chip for long-term cultivation and substance testing proven by 3D human liver and skin tissue co-culture
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Fiber Optic Sensor Designs and Luminescence-based Methods for the detection of Oxygen and pH measurement
Optical, and especially fiber optic techniques for chemical sensing have become very attractive in recent decades for a wide variety of biomedical and industrial processes and considerable progress in research in this field has been seen, evidenced by the significant number of papers published over several decades, commercial products developed and marketed and which continuing to be produced. This work extends the body of knowledge in the field and focuses on two industrially-important ‘chemical’ measurands: the determination of pH level and oxygen concentration (O2) - both are critically important for a broad range of applications globally, in fields as diverse at the life sciences, environmental monitoring, biomedical research and thus widely across industry.
The many different optical platform designs and fabrication methods that have been developed are considered, including those for commercial applications, recognizing the wide range of industrial and scientific uses, and their performance compared. Further, the effect of specific fiber structures on sensor performance, e.g. on sensitivity, response time and long-term stability, and possible applications also has been analyzed. Applications are seen in difficult and ‘niche’ measurement environments to which conventional sensors are often not well suited, taking advantage of their lightweight nature, ease of miniaturization, potential to be multiplexed and low cost. Through a discussion of representative techniques that have reached commercial development, a comprehensive and state-of-the-art view of this exciting and important field is possible
Raman Imaging with a Fiber-Coupled Multichannel Spectrograph
Until now, spatially resolved Raman Spectroscopy has required to scan a sample under investigation in a time-consuming step-by-step procedure. Here, we present a technique that allows the capture of an entire Raman image with only one single exposure. The Raman scattering arising from the sample was collected with a fiber-coupled high-performance astronomy spectrograph. The probe head consisting of an array of 20 × 20 multimode fibers was linked to the camera port of a microscope. To demonstrate the high potential of this new concept, Raman images of reference samples were recorded. Entire chemical maps were received without the need for a scanning procedure