Microfluidic devices have not yet evolved into commercial off-the-shelf products. Although highly integrated microfluidic structures, also known as lab-on-a-chip (LOC) and micrototal-analysis-system (µTAS) devices, have consistently been predicted to revolutionize biomedical assays and chemical synthesis, they have not entered the market as expected. Studies have identified a lack of standardization and integration as the main obstacles to commercial breakthrough. Soft microfluidics, the utilization of a broad spectrum of soft materials (i.e., polymers) for realization of microfluidic components, will make a significant contribution to the proclaimed growth of the LOC market. Recent advances in polymer science developing novel stimulus-active soft-matter materials may further increase the popularity and spreading of soft microfluidics. Stimulus-active polymers and composite materials change shape or exert mechanical force on surrounding fluids in response to electric, magnetic, light, thermal, or water/solvent stimuli. Specifically devised actuators based on these materials may have the potential to facilitate integration significantly and hence increase the operational advantage for the end-user while retaining cost-effectiveness and ease of fabrication. This review gives an overview of available actuation concepts that are based on functional polymers and points out promising concepts and trends that may have the potential to promote the commercial success of microfluidics.

Thermocouples classically consist of two metals or semiconductor components that are joined at one end, where temperature is measured. Carbon black is a low-cost semiconductor with a Seebeck coefficient that depends on the structure of the carbon particles. Different carbon black screen-printing inks generally exhibit different Seebeck coefficients, and two can therefore be combined to realize a thermocouple. In this work, we used a set of four different commercially available carbon-black screen-printing inks to print all-carbon-black thermocouples. The outputs of these thermocouples were characterized and their Seebeck coefficients determined. We found that the outputs of pure carbon-black thermocouples are reasonably stable, linear, and quantitatively comparable to those of commercially available R- or S-type thermocouples. It is thus possible to fabricate thermocouples by an easily scalable, cost-efficient process that combines two low-cost materials.

This work deals with the realization of a fully printed thermocouple-array on a flexible substrate for condition monitoring applications. The thermocouple-array consisting of carbon black and silver was fabricated on PET-foil in a screen printing process and characterized up to a junction temperature of 150 °C. To ensure that no spurious voltages of the thermocouple occur due to deformations of the flexible substrate, the cross-sensitivity to deformation of the foil was investigated as well. Finally, as a test case, the temperature gradient of a plastic bar heated on a single end was measured with the thermocouple-array.

We investigate the feasibility of viscosity and density measurements using diamagnetically stabilized levitation of a floater magnet on pyrolytic graphite. This principle avoids any clamping structures in the measurement chamber and is, therefore, not suffering under unknown mounting conditions and is furthermore easy to integrate into microfluidic systems. The only part that has to be in contact with the liquid is the floater magnet. Immersing it in a liquid, buoyancy forces will come into play. Keeping the levitation height of the floater magnet constant in different liquid surroundings by accordingly adjusting the lifter magnet, the buoyancy force and, therefore, the density of the fluid can be determined from these adjustments. For more accurate results, a magnetic field modeling was used to determine the levitation height of the floater magnet out of the superposed magnetic fields of both magnets. For viscosity measurements, we add an additional ac-driven coil to the setup, which yields a superposed alternating force on the floater magnet causing periodic vibrations of the floater magnet. The vibrations are damped according to the viscosity of the surrounding fluid. By performing a frequency sweep, the frequency response of the damped spring mass resonator can be obtained where the resonance frequency for our setup is around 6 Hz. Furthermore, the influence of the levitation height on the resonance characteristics was examined by studying the resonance frequency and quality factor for different lifter magnet positions.

The selection of appropriate signal labels is a central consideration in electrochemical biosensing as it directly determines the achievable detection limits, dynamic range, and overall analytical performance. Conventional electroactive labels require low operating potentials, fast electron-transfer kinetics, and reliable attachment to electrode surfaces or recognition elements. Despite their extensive use, these labels present notable challenges for point-of-care applications, particularly in the detection of small molecules where target binding does not inherently generate a measurable electrochemical output. As a result, most sensing architectures depend on externally added redox reporters, introduced either freely into solution or covalently linked to recognition structures, which increases assay complexity and limits scalability. These limitations have motivated the transition toward energy-based electrochemical signal pathways, such as the hydrogen evolution reaction (HER), oxygen reduction reaction (ORR), and water-splitting reactions. These reactions provide intrinsic electrochemical outputs that eliminate the need for synthetic redox mediators and can operate as built-in catalytic signal sources. Their integration into biosensing platforms simplifies assay design, enhances robustness, and broadens compatibility with diverse target molecules. This review outlines the mechanistic basis connecting HER/ORR/water-splitting reactions to signal generation in biosensors and highlights material design principles that enable their use as reagentless and label-free transduction strategies. Compared with traditional electroactive labels, energy-driven approaches offer simplicity, reduced cost, faster operation, and improved suitability for commercial translation. By establishing a unified framework for energy-based electro-recording mechanisms, this review aims to promote the development of next-generation bioanalytical methods that operate without electroactive labels and expand the applicability of electrochemical biosensing across various domains.