Healthcare, soft robotics, and battery management are only three examples of sensor solutions that measure the spatial and temporal distribution of temperatures and local heat flux. Thermistors and thermocouples (TCs) can both be realized by
printing technologies. Combining screen printing, inkjet printing, and aerosol jet printing enables a unique combination of large-area processing and high-resolution fabrication. We have realized printed temperature sensor arrays using a printable thermoresistive polymer with several hundred individual sensors. We have recently demonstrated its application as an additional computer security feature for microprocessors [1]. As an alternative to organic sensor materials, inorganic nanomaterials are promising for thermal sensing applications based on thermoelectric principles. We have realized thermocouples as sensor arrays based on mechanically flexible substrates [3]. We used high-performance (SbBi)2(TeSe)3-based printed flexible TE materials to fabricate two types of shape-conformable TC-based temperature sensor arrays with 25 pixels.
Bragg mirrors play an essential role in various optical and photonic devices. The fabrication of Bragg mirrors is mainly done by physical and chemical vapor deposition, which are costly and do not allow for lateral patterning. Here, we demonstrate a versatile and straightforward method to realize the fabrication of Bragg mirrors by fully inkjet printing using a commercial desktop printer. The reflectance peaks of the Bragg mirrors reach 99% with ten uniform bilayers. The central wavelength of the Bragg mirrors is tuned by adjusting printing parameters. With our method, laterally-patterned Bragg mirrors are successfully printed on large and flexible foils.
High performance X-ray detectors can be realized by a variety of different approaches. However, more and more attention is paid to direct conversion X-ray detectors in a planar device geometry that use hybrid organic-inorganic perovskite semiconductors as absorber material. This study follows an alternative approach and uses a folded instead of a planar device architecture in order to realize a high performance X-ray detector. By reporting on the fabrication of a foldable perovskite sensor array and by demonstrating a high X-ray sensitivity and a high spatial resolution when the array is folded, we prove the concept of the folded perovskite detector design.
We present a fully printed temperature array yielding a total of 625 sensor pixel on a 12 mm by 12 mm area. Screen and aerosol jet printing are combined to fabricate the sensor stack. The active area features a bottom and top silver electrode sandwiching a thermoplastic based thermistor material. Due to the robust behavior towards humidity no encapsulation or special treatment was necessary. The sensor was operated between 0°C to 110°C exhibiting measurement accuracy of +/- 1°C. As demonstration, a laser was used to heat the sensor array locally and its beam properties and diameter could be observed.
We demonstrate the suitability of two cost efficient technologies, namely roll-to-roll hot embossing and laser-assisted hot embossing, to fabricate arrays of structures in the microscale down to the sub-100 nm range. We therefore employ polymers with a relatively moderate glass transition temperature, e.g., cyclic olefin copolymer (COC) and polystyrene (PS). We compare the two replication processes regarding their precision and cost using different 1D and 2D nanostructure gratings and microfluidic channels. All nickel shims used for the replication are fabricated in combination of electron beam or UV lithography and nickel electroforming. The replicated structures are used in different applications. The nanopillar arrays are coated with gold and integrated in the hot embossed microfluidic channels for lab-on-a-chip (LoC) surface-enhanced Raman analysis. We evaluate the as-fabricated 2D nanopillar arrays for surface-enhanced Raman spectroscopy (SERS) using solutions of rhodamine 6G as exemplary analytes. The influence of the geometrical parameters like diameter and pitch of the polymer structures as well as the influence of the gold layer thickness are discussed. 1D-gratings will be used as resonators for organic distributed feedback (DFB) lasers. Both elements, the SERS chips and the organic DFB lasers as tunable excitation source can be combined in the future to form one Raman-on-Chip optofluidic platform for sensitive detection of low-concentrated analytes in water.
The individualized functionalization of mass-produced microstructures is still challenging for the process technology. Here, a rroll-to-roll based process hot embossing is presented for the production of microfluidic structures by means of hot embossing is presented. The resulting microfluidic channels are functionalized modified with different materials. Thereby, digital printing technologies such as aAerosoljet or inkjet are used. This approach allows for mass production of microfluidic channels and their the individualized individual functionalizationfunctionalization of mass produced microfluidic channels. The encapsulation of the channels also takes placeis realized in an R2R-based thermal bonding process without adding any solvent or adhesive.
Taking account ofUsing this approach, several sensor systems for gas and / or fluid detection could be demonstrated. Surface -eEnhanced Raman Scattering scattering (SERS) with amplification enhancement factors of up to 107 [1] is demonstrated by printing gold nanoparticles into the microfluidic channel. We evaluate the printed SERS structures using solutions of rhodamine 6G and adenosine as exemplary analytes.
Furthermore, these channels could be functionalized with different fluorescent organic semiconductors. Their fluorescence intensity is quenched in the presence of a nitroaromatic compounds. By using different materials simultaneously, we are able to measure a fingerprint like pattern of different analytes, which we evaluated by means ofusing pattern recognition algorithms. This method can be used both in the gas phase (electronic nose) and in fluids (electronic tongue) for the detection of nitroaromatic compounds [2,3]. With the opto-electronic nose, we were able to reach detections limits below 1ppb.
[1] A. Habermehl et al, Sensors 17, 2401 (2017).
[2] N. Bolse et al, Flexible and Printed Electronics 2, 024001 (2017)
[3] N. Bolse et al, ACS Omega 2 (10), 6500-6505 (2017)
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