Automated Quantitative Quality Assessment of Printed Microlens Arrays

We propose an automated evaluation pipeline uti-lizing both bright field light and confocal microscope imagesas well as multiple quality measures to quantitatively evaluatethe quality of printed microlens arrays

High Dynamic Range Smart Window Display by Surface Hydrophilization and Inkjet Printing

Mechanoresponsive smart windows have been intensively investigated in recent years as they offer various applications for signage and light management. However, integrating a display functionality into such smart windows remains a challenge since the realization of pixels in these devices is difficult. In addition, mechanoresponsive smart windows with a high dynamic range are rarely demonstrated because they would suffer from complex fabrication processes and high costs. In this work, a novel surface modification process and digital encoding were developed for direct inkjet printing of micro-etching-masks on hydrophobic elastomers, and a pixelated haze distribution was realized. Compared to the traditional mechanoresponsive smart windows, which modify the optical performance by applied strain solely, here, a smart window with haze tunability in either static or strain-applied state is demonstrated. The work enhances the potential of the fabricated smart window to be applied in high dynamic range signage displays

Freeform terahertz structures fabricated by multi-photon lithography and metal coating

Direct-write multi-photon laser lithography (MPL) combines highest resolution on the nanoscale with essentially unlimited 3D design freedom. Over the previous years, the groundbreaking potential of this technique has been demonstrated in various application fields, including micromechanics, material sciences, microfluidics, life sciences as well as photonics, where in-situ printed optical coupling elements offer new perspectives for package-level system integration. However, millimeter-wave (mmW) and terahertz (THz) devices could not yet leverage the unique strengths of MPL, even though the underlying devices and structures could also greatly benefit from 3D freeform microfabrication. One of the key challenges in this context is the fact that functional mmW and THz structures require materials with high electrical conductivity and low dielectric losses, which are not amenable to structuring by multi-photon polymerization. In this work, we introduce and experimentally demonstrate a novel approach that allows to leverage MPL for fabricating high-performance mmW and THz structures with hitherto unachieved functionalities. Our concept exploits in-situ printed polymer templates that are selectively coated through highly directive metal deposition techniques in combination with precisely aligned 3D-printed shadowing structures. The resulting metal-coated freeform structures offer high surface quality in combination with low dielectric losses and conductivities comparable to bulk material values, while lending themselves to fabrication on planar mmW/THz circuits. We experimentally show the viability of our concept by demonstrating a series of functional THz structures such as THz interconnects, probe tips, and suspended antennas. We believe that our approach offers disruptive potential in the field of mmW and THz technology and may unlock an entirely new realm of laser-based 3D manufacturing

Fully Printed Temperature Sensor Array Comprising 625 60×60 µm2 pixels

Abstract With further digitalization and automation, new applications fields require new solutions and sensors. Healthcare, soft robotics, and battery research are only three examples striving for sensor solutions capable of measuring the spatial and temporal temperature distribution of surfaces. This requires the deposition of multiple sensor pixels with a high spatial resolution on potentially flexible substrates. Printing technologies are well suited to fulfill the associated requirements of quality, speed, feature size, and costs. Combining screen printing and aerosol jet printing allows for fast large‐scale processing and when needed high‐precision fabrication for small features. The presented high‐density temperature sensor array provides 625 sensor pixels with a size of 60×60 µm2, evenly distributed over an area of 12×12 mm2. The sensor is operated without encapsulation between 5 and 90 °C showing an average deviation of less than 0.5 °C. The sensor stack consists of a bottom and top electrode sandwiching a carbon black based thermistor layer. The material shows a strong negative‐temperature‐coefficient (NTC) effect with a sensitivity of 3.6 % °C−1 at 5 °C. As an application example, the temperature profile induced by a laser beam is mapped with the temperature sensor array