BACKGROUND:Traditional control of continuum robots (CRs) and hyper-redundant robots (HRRs) typically relies on large, costly consoles to capture physician input. This raises the question of whether such systems can be simplified without losing functionality. METHODS:A low-cost, real-time control system was developed for a 7-DoF CR/HRR using a handheld, pencil-like wireless handle equipped with only two passive optical markers. The handle directly controls 5 DoF, while the remaining 2 DoF are resolved through null-space projection for length minimisation and a roll-compensation method that maintains horizontal endoscopic image alignment. RESULTS:The system enabled effective real-time control of a redundant 7-DoF CR/HRR using only two tracked markers. The supplementary constraints successfully managed redundancy, minimised robot length, and preserved horizontal imaging. CONCLUSIONS:This work presents a compact two-marker input device, a null-space-based length-minimisation strategy, and a roll-compensation method for endoscopic imaging.

This paper investigates the performance of ruled diffraction gratings in the bulk material RSA-501. RSA-501 is a rapidly solidified aluminium alloy with an ultra-fine grain structure that meets the optical and nano-structuring requirements. The aim is to investigate ruled diffraction gratings of RSA-501 regarding their diffraction efficiency, stray light, and structure. Individual grooves, groove arrays, and whole diffraction gratings were fabricated using ruling. Using the bulk material RSA-501 instead of a coating has the advantage that sample preparation by means of flycutting and ruling can be carried out on the same ultra-precision machine tool. This eliminates the need for the cost-intensive and time-consuming preparation of the workpiece by polishing and coating, and avoids re-mounting errors, as a monolithic fabrication is possible. The generated structures were measured by AFM, SEM, and a self-developed optical measuring setup. Results show RSA-501’s suitability for ruled diffraction gratings, with a roughness of the blaze facets that matches the diamond tool’s roughness. Deviations in the vertical positions of groove valleys were identified, which are mainly responsible for the stray light. Ruling performed with shallow blaze angles α ≤ 3° led to a rounding of the blaze facets. This rounding was also observed for individual grooves with larger blaze angles of α ≥ 4°, but the rounding did not occur when the structures were produced in an array. The structure quality and diffraction efficiency of ruled diffraction gratings in RSA-501 lie between those of shaped gratings and gratings produced in complex and less economical ruling process chains. Rapidly solidified aluminium RSA-501 is suitable for ruling diffraction gratings Using a bulk material allows ruling and the sample preparation on the same machine Efficiency lies between shaped gratings and thin-film ruling process chains Stray light results from the deviation of the groove valley position Ruling of small blaze angles α ≤ 3° result in a rounding of the blaze facets

This study presents a unique experimental comparison of a multi-jet spray cooling unit and a parallel microchannel evaporator, both integrated into the same compact R-1234yf vapor compression refrigeration system with an oil-free linear compressor. Previous studies have not compared these technologies side-by-side under identical conditions. This work fills that gap by testing both configurations in the same facility, with matched heat transfer surface areas and calibrated flow restrictions to ensure an unbiased comparison. The spray unit merges evaporator and expansion functions, delivering subcooled refrigerant through oblique orifices to form impinging two-phase jets on a heated surface. The microchannel system employs a needle valve and a copper evaporator with 34 channels (260.7 mu m hydraulic diameter), with the valve configured to match the spray unit's flow coefficient. Tests covered refrigerant charges from 29.9 to 143.6 g and thermal loads from 25 to 250 W. Both systems maintained surface temperatures below 70 degrees C. The spray unit outperformed at high heat fluxes, achieving higher critical heat flux and lower surface temperatures, while the microchannel unit was more effective at low to moderate loads. Maximum heat transfer coefficients on the order of 43 kW/(m2K) were achieved with spray cooling, versus 37 kW/(m2K) for the microchannel system, though at significantly lower wall heat flux. Thermal performance was benchmarked against classical pool boiling correlations, which serve as reference standards for immersion cooling. Both systems exceeded these baselines, with the spray unit maintaining higher heat transfer coefficients up to critical heat flux levels.

Inverse kinematics is a core problem in robotics, involving the use of kinematic equations to calculate the joint configurations required to achieve a target pose. This study introduces a novel inverse kinematic model (IKM) for extensible (i.e., length-adjustable) continuum robots (CRs) and hyper-redundant robots (HRRs) featuring an elbow joint. This IKM numerically solves a set of equations representing geometric constraints (abbreviated as NSGC). NSGC can handle target poses Xt=[xt,yt,zt,ψt] in 3D space, which are projected onto a 2D plane and solved numerically. NSGC is capable of real-time operation and accounts for elbow joint limits. Extensive simulations and empirical tests confirm the reliability, performance, and practical applicability of NSGC.

This publication presents an improved manufacturing method for tetrahedral metal effect pigment particles that demonstrates reduced flowlines in injection-molded polymer components compared with conventional platelet-shaped pigment particles. The previously published cold forming process for tetrahedral particles, made entirely from aluminum, faced manufacturing challenges, resulting in a high reject rate due to particle adhesion to the micro-structured mold roller. In contrast, this study introduces a new manufacturing method for tetrahedral particles, now consisting of metallized UV-cured thermoset polymer. These particles, dispersed in amorphous matrix thermoplastics, have shown to maintain their shape during the injection molding process. The manufacturing technique for these novel particles is based on UV imprint lithography, omitting the reject rates compared with the previously presented cold rolling process of tetrahedral full aluminum particles. Thus, the novel manufacturing technique for tetrahedral pigment particles shows increased potential for automation through roll-to-roll manufacturing in the future.

Photocatalytic hydrogen evolution is a direct pathway to store solar energy in chemicals. Conjugated microporous polymers (CMPs) are porous organic photocatalysts, that are typically applied in powder form in heterogenous catalytic reactions. However, the use of powder photocatalysts in dispersion poses some major challenges when it comes to practical applications in larger scales. In this manuscript, the photocatalytic performance of a carbazole-based porous organic polymer (C-POP) film produced by electro polymerizing 1,2,3,5-Tetrakis(carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN) is investigated, well-known for its intriguing photocatalytic properties. The thickness of the intrinsic microporous film is tuneable by the amount of cyclic voltammetry cycles but it is shown that the hydrogen production is not dependent on film thickness. It can therefore be concluded that catalysis is mainly occuring on the outer surface of the films, questioning whether high surface areas are always required for efficient photocatalysis. A microstructured film offers the advantage that, with a reduced amount of polymer material, a constant or even increased external surface area of the film can be achieved. The approach presented here is therefore advantageous for achieving high hydrogen production per unit area with minimal amounts of polymer, as very thin layers are already sufficient for high activity.

The textile industry is highly competitive, with decreasing production costs and increasing disposal of clothes. Currently, such items are mostly combusted, disposed, or downcycled into lower value products like fleece, posing an ever-increasing demand on (fossil) resources and energy. Only a small share of garments is reused, as the sorting process is traditionally performed by trained personnel, resulting in significant time consumption. The method presented here employs computer vision and artificial intelligence for textile pre-sorting, significantly enhancing the proportion of reusable textiles. The method relies on a custom high-resolution camera system that captures images of textiles and garments on a conveyor belt. The system not only recognizes the type but also infers the quality as well as the fabric type of garments, ensuring high-quality sorting and substantially increasing the proportion of textiles that can be reused. The presented approach of fabric detection in visually inspected objects has potential applications beyond post-consumer sorting, such as in electronics and plastics recycling. It can also be applied to manufacturing tasks across various industries-including agriculture, food, and automotive-enhancing quality control, reducing waste, increasing efficiency, and thus supporting the principles of a circular economy.

This research group has been demonstrating the significant advantages of using Nb2O5 coatings for functionalizing titanium, aluminium, and stainless steels. Regarding the biomedical sector and considering Ti-6Al-4V alloy, the reactive sputtering technique improved the cell viability, the osteogenic performance of cells involved in the osseointegration process as well as the ability to delay bacterial proliferation. The characteristics of the Nb2O5 coatings were assessed before by using standard methods, which provide information only a few tens of nanometers depth. Given that the Nb2O5 coating fabricated in this work exhibits a thickness of approximately 300 nm, the GE-XANES technique emerges as the most suitable method for this analysis. Additional information was provided with the aid of nanoindentation load-depth (P-h) curves. GE-XANES results indicated the formation of a homogeneous layer of Nb2O5 coating on the Ti-6Al-4V surfaces. The deposition process improved the surface hardness of the Ti-6Al-4V alloy (4.38 GPa versus 5.62 GPa) considering the 2 mN load.

Spectroscopy has emerged as an essential technology, particularly in decentralized utilization within point-of-care devices. These applications demand compact, cost-effective designs with reduced complexity compared with traditional laboratory equipment. Achieving compactness often involves minimizing the number of components, necessitating that each remaining component fulfills multiple functions to optimize performance. However, this approach can lead to significant aberrations due to constructive compromises. Nevertheless, the known phase errors enable correction, often achieved directly through diffractive elements. Diffractive compensation of aberrations is commonly conducted through interference lithography, exploiting holographic techniques to produce gratings without explicit knowledge of the interference structure. Alternatively, mechanical manufacturing techniques offer the possibility of producing blazed gratings with greater efficiency. However, diffractive correction using mechanically fabricated gratings requires a precise understanding of individual groove trajectories, presenting an ongoing challenge. We employed ultraprecision (UP) mechanical manufacturing techniques to create aberration-corrected diffraction gratings for spectroscopic applications. To enable the machining of freeform trajectories, facilitating versatile fabrication of both planar and concave imaging blazed gratings, a modified five-axis UP machinery is employed. To correct the known wavefront errors of the exemplary use cases, a nonlinear phase function was applied and a numerical method was developed to derive trajectories from the phase errors and translate them into machine code. The use cases are a blazed imaging planar Littrow grating and concave Rowland gratings, showcasing corrected astigmatic wavefront deviation. The theoretical and experimental results are compared and discussed. (c) The Authors. Published by SPIE under a Creative Commons Attribution 4.0 International License.

Given the limited availability of off-the-shelf continuum robots (CRs), researchers and engineers must design their own and tailor them to their specific use case requirements. Questions such as the following arise: What is the minimum length of the CR needed to achieve the desired dexterous workspace? And where should the robot be ideally located with respect to the workspace? These questions are answered for a single-port setup in this paper. A projection-based method is introduced that maps the dimensionality of the required workspace from 3D to 1D, exploiting the remaining degrees of freedom preserved in a single-port procedure. Then, a set of equations for the most critical point in the workspace is described, representing the geometry of both the CR and the workspace. A bounded, non-linear optimization approach is implemented, computing the global minimum of this set of equations. This method is simulated and tested for a length-extensible, multi-backbone CR. To the best of the authors’ knowledge, this is the first time a desired dexterous workspace has been empirically verified for a CR. Furthermore, the prototype features novel design elements that solve relevant mechanical challenges in the state-of-the-art

This article presents an electrodynamic converter with competitive operating characteristics compared to conventional electric machines, good scalability, and inexpensive manufacturing. The converter is suitable for being used in a variety of applications as an efficient and effective generator or motor. The introduced prototypical converter is a two-phase ex-ternal tooth pole machine with a permanently excited rotor and toroidal coils on the stator. The machine is based on the claw pole principle and has tooth pole pairs. The two subsystems have an electrical offset of 90 degrees to one another, and each of them generates a torque that pulsates over time. The rows of rotor teeth in each system have an electrical offset of 180 degrees to one another. A soft magnetic composite material is used to guide the magnetic flux in all three directions. The prototype generates a voltage of 30 V per coil at a speed of 1500 rpm and produces an extrapolated power of 350 W.

The production of mold inserts for the replication of micro-lens arrays through micro-embossing could be an alternative process route compared to diamond turning or milling in order to reduce time and costs. The rapidly solidified aluminum alloy RSA-501 is expected to form micro-structures with low surface roughness because of its ultra-fine grain structure. In micro-embossing challenges like elastic spring back effect, pile-ups, and forming accuracy depend on the material behavior. Therefore, RSA-501 was further characterized and the influence of polishing or flycutting on the material behavior was investigated. To further understand the grain and microstructure samples were sectioned along their cross and longitudinal directions. The grain structure of RSA-501 was oriented along the extrusion direction and the mean grain sizes were <1.00 μm. Furthermore, RSA-501 was micro-embossed to investigate the influence of the material behavior and surface preparation on the forming of micro-structures. The induced surface integrity through flycutting was not deep enough to influence the forming of micro-structures. Therefore, the workpiece surface can be prepared either by polishing or flycutting. When micro-embossing RSA-501, cross and longitudinal sections can be used. However, it is recommended to process the cross section because of its isotropic grain structure. It was shown that the curvature radius of micro-embossed concave structures differs from the tool radius. This is due to the elastic spring back effect. Since the embossed structure remains spherical, the spring back effect can be compensated by adjusting the tool radius.

Zusammenfassung Dieser Beitrag stellt einen elektrodynamischen Wandler vor, der im Vergleich zu konventionellen E‑Maschinen wettbewerbsfähige Betriebseigenschaften aufweist, beliebig skalierbar und kostengünstig herzustellen ist. Der Wandler ist geeignet, in vielfältigen Anwendungen als effizienter und effektiver Generator oder Motor eingesetzt zu werden. Der hier vorgestellte prototypische Wandler ist eine zweiphasige Außenläufer-Zahnpolmaschine mit permanenterregtem Rotor und Ringspulen am Stator. Die Maschine ist an das Klauenpolprinzip angelehnt und besitzt Zahnpolpaare. Der Versatz der beiden Teilsysteme zueinander beträgt elektrisch 90°, und sie erzeugen jeweils ein zeitlich pulsierendes Drehmoment. Die Rotorzahnreihen jedes Systems weisen jeweils einen elektrischen Versatz von 180° zueinander auf. Ein weichmagnetischer Kompositwerkstoff wird verwendet, um den magnetischen Fluss in allen drei Raumrichtungen führen zu können. Der Prototyp generiert pro Spule bei einer Drehzahl von 1500 U/min eine Spannung von 30 V und erzeugt eine extrapolierte Wirkleistung von 350 W.

Since its introduction in the 1980s, 3D printing has advanced as a versatile and reliable tool with applications in different fields. Among the available 3D printing techniques, two-photon polymerization is regarded as one of the most promising technologies for microscale printing due to its ability to combine a high printing fidelity down to submicron scale with free-form structure design. Recently, the technology has been enhanced through the implementation of faster laser scanning strategies, as well as the development of new photoresists. This paves the way for a wide range of applications, which has resulted in an increasing number of available commercial systems. This work aims to provide an overview of the technology capability by comparing three commercial systems in a round-robin test. To cover a wide range of applications, six test structures with distinct features were designed, covering various aspects of interest, from single material objects with sub-micron feature sizes up to multi-material millimeter-sized objects. Application-specific structures were printed to evaluate surface roughness and the stitching capability of the printers. Moreover, the ability to generate free-hanging structures and complex surfaces required for cell scaffolds and microfluidic platform fabrication was quantitatively investigated. Finally, the influence of the numerical aperture of the fabrication objective on the printing quality was assessed. All three printers successfully fabricated samples comprising various three-dimensional features and achieved submicron resolution and feature sizes, demonstrating the versatility and precision of two-photon polymerization direct laser writing. Our study will facilitate the understanding of the technology maturity level, while highlighting specific aspects that characterize each of the investigated systems.

Optical elements made of aluminum with surface roughness in the sub-nanometer range are required for applications in the visible (VIS) and ultraviolet (UV) spectral range. Rapidly solidified aluminum (RSA) 501 is an interesting candidate to produce sufficiently smooth surfaces for these applications in an ultra-precision (UP) flycutting process. However, the polycrystalline grain structure and precipitates contained in the material limit the achievable surface roughness. In this research, a reactive ion beam finishing process of RSA 501 is investigated employing an electron cyclotron resonance (ECR)-driven ion source using CF4 and N2 gasses. Emphasis is placed on understanding the etching mechanisms that influence the topographic evolution to provide the basis for future production processes using the material for UV optics. Material composition characterization is applied to analyze the interaction between the reactive ion species and the RSA material. Surface modification transferring the native oxide top layer to an in situ forming and developing aluminum fluoride or -nitride etch front layer is found to prevent grain orientation-dependent etching. The effect of the ion incidence angle on the etch rates of precipitates and bulk material can be used to reduce the height of precipitates protruding from the surface after the UP-machining process. A surface roughness value of Sq = 0.9 nm +/- 0.1 nm (areal root mean square height) is achieved in the micro-roughness range when etching at 40 degrees and 80 degrees angle of incidence using collimated ion beams with CF4 process gas.

Gallium Phosphide (GaP) is a semiconductor with advantageous optical properties for near- and middle infrared optical systems. However, optical applications of GaP are limited by its current low machinability. To cut brittle semiconductors such as GaP and generate optical quality surfaces, it is necessary to induce a High-Pressure Phase Transformation (HPPT) so that a phase is formed that behaves ductile when machined. Along the cutting process this can be achieved by applying a negative rake angle. Otherwise, cracks will appear on the machined surface, worsening its optical capabilities. A HPPT of GaP happens at an atomic scale when a zincblende structure changes into a β-tin one. The β-tin structure behaves ductile and is metastable. Hence, the metastable β-tin phase cannot be observed during the cutting process. Therefore, atomistic simulation, such as Classic Molecular Dynamics Simulation (CMDS), is required to study the machinability under HPPT. In this work, CMDS were used to analyze GaP cutting mechanisms. A diamond tool was modelled with a cutting edge radius rβ = 10 nm, rake angle γ = -20 º, and clearance angle α = 10 º. The cut was performed with a depth of cut ap = 12 nm along the [100]-direction in a zincblende GaP workpiece. Stacking faults were found on the shear zone, {111}-planes, by two different post processes approaches. HPPT was found in the deformation zone only. A stagnation zone was found in front of the cutting edge proceeding a crack nucleation.

Artificial intelligence (AI) has already been the subject of extensive scientific and industrial research in order to solve current challenges in intelligent manufacturing. However, these approaches often do not yet reach industrial small and medium-sized enterprises (SMEs). To meet the demand for resilient and sustainable production processes, the aim is to develop concepts to transfer applications into cyber physical production systems. Therefore, AI methods can be introduced as part of a smart manufacturing chain. In this work, an infrastructure to efficiently handle production data which is independent of the individual production process such as machining, grinding or electrical discharge machining is presented. Subsequently, an exemplary roadmap for SMEs is given to establish AI applications within the scope of manufacturing industry 4.0. As a result, an increase in efficiency and profitability of individual production processes as well as the overall production chain can be achieved.

In this study, novel micro particles in the shape of irregular tetrahedrons in a two to three-digit micrometer size range are presented. The particle manufacturing feasibility was investigated in three different ways: shaping, casting and rolling. Rolling showed the potential for mass production. The suitability of tetrahedral particles for the use as metal effect pigment was assessed by comparison with conventional platelet-shaped metal effect pigments. Optical inspection showed a strongly reduced luminance inhomogeneity in weld line regions in the case of the tetrahedral particles. It was found by synchrotron X-ray tomography examination of particles in solidified polymethylmethacrylate (PMMA) that particle depletion is not the main reason for visible flow lines. The orientation of platelet-shaped pigment particles was identified to cause such flow lines. PMMA filled with tetrahedral particles, in contrast, shows homogenous optical properties independent from the particle orientation. Thus, flow lines in weld line regions can be omitted.

The production of mold inserts for the replication of micro-lens arrays through micro-embossing could be an alternative process route compared to diamond turning or milling in order to reduce time and costs. The rapidly solidified aluminum alloy RSA-501 is expected to form micro-lenses with low surface roughness because of its ultra-fine grain structure. In micro-embossing challenges like elastic spring-back-effect, pile-ups and forming accuracy depend on the material behavior. Therefore, RSA-501 was further characterized and the influence of polishing or flycutting on the material behavior was investigated. To further understand the grain and microstructure samples were sectioned along their cross and longitudinal directions. The grain structure was investigated through metallographic analysis and EBSD measurements. SEM micrographs and EDS were used to analyze the precipitations, their distribution and size. The influence of the surface preparation method was investigated through nanoindentation and SEM micrographs of specimens prepared by using a focus ion beam to measure their depth of the surface integrity. Furthermore, RSA-501 was micro-embossed to investigate the influence of the material behavior and surface preparation on the forming of micro-lenses. The grain structure of RSA-501 was oriented along the extrusion direction. The mean grain sizes were < 1.00 µm. The induced surface integrity through flycutting was not deep enough to influence the forming of micro-lenses. Therefore, the workpiece surface can be prepared either by polishing or flycutting. When micro-embossing RSA-501 cross and longitudinal sections can be used. However, it is recommended to process the cross section because of its isotropic grain structure.

Engineering education today is often organised in discipline-specific modules. Although it is essential to build up basic knowledge, cross-disciplinary knowledge is fundamental for solving complex problems. Transdisciplinary approaches can provide the necessary hard and soft skills, improve self-determination in education and broaden personal competence profiles. The experience gained is conveyed using the example of project-based modules on the topics of a) AI applications to minimise racial biasing in medical technology and b) construction of microfluidic systems to avoid animal testing. These were developed over several semesters by interdisciplinary student groups involving industry and research partners. The concept was initially carried out online in an interdisciplinary project module focusing on individual learning objectives, composed of the disciplines "Mechanical Engineering", "Computational Engineering Science", "Physical Engineering Sciences" as well as "Biomedical Engineering" and is being expanded in a hybrid-transdisciplinary manner through gradual additions including systems engineering, philosophy and sustainability in technology, ergonomics and human-machine systems. Through active participation in researching and solving real challenges, collaboration of transdisciplinary teams over several group generations and setting individual learning goals, profound knowledge and new methodological competences can be acquired beyond engineering disciplines. The integration of non-technical methods and approaches allows students to recognise complex problems and identify the necessary competences in order to realise a successful project. To further expand this approach, a new module concept for interdisciplinary cooperation in production engineering was developed. It takes up the aspects of individual, project-based learning and brings together all the competences of the institute in transdisciplinary exchange.