Frank Goldschmidtboeing

Smart materials that can sense and react to environmental stimuli are enabling technologies for use in healthcare devices, soft robotics, aerospace and microelectromechanical systems. Among these, paraffin-based phase change material (PCM) actuators have received significant attention due to their high mechanical energy density, affordability and versatility. However, their low thermal conductivity generally limits heat transfer, resulting in slow response times and hindering multifunctional integration. This study presents a dual-paraffin thermoelectric generator-PCM (TEG-PCM) actuator comprising controllable actuation, thermal energy storage and thermoelectric energy harvesting within a leakproof PCM-PDMS matrix. The system uses two paraffins with complementary functions. A low-latent heat paraffin (P1), enhanced with 1 wt.% graphene nanoplatelets (GnP), was filled into a copper cavity and optimized for actuation. A high-latent heat paraffin (P2), embedded in a PDMS matrix, provides thermal stabilization and heat storage. A TEG couples these two functions, enabling Peltier-driven actuation and reset as well as energy harvesting from external temperature gradients via the Seebeck effect. Micro-computed tomography and differential scanning calorimetry revealed that 30 wt.% P2 content offered the optimal balance between latent heat storage and mechanical integrity, with no leakage over multiple thermal cycles. The dual paraffin actuator exhibited maximum displacements and forces of 1400 μ m and 150 mN, with response times of 208 s cm − 3 , representing a fivefold improvement over comparable paraffin-PDMS actuators. Directional infrared heating produced temperature differentials of up to 8 ∘ C and open-circuit voltages of approximately 27 mV, corresponding to an estimated maximum power output of ∼ 228 μ W under matched-load conditions. When employed as an autonomous thermal switch, the actuator uses the P1-GnP expansion to temporarily bridge a thermal gap, thus doubling the thermoelectric output voltage. This multifunctional device couples autonomous and controllable actuation with thermoelectric energy conversion, representing a promising building block towards multifunctional systems for high-temperature microfluidic and thermal management applications.

Oxygen-releasing anthracene-endoperoxide (ANT-EPO) systems provide a chemical route to self-contained gas generation, but their use as pressure sources requires a quantitative description of how reaction kinetics, gas–liquid partitioning, and chamber geometry determine pressure buildup in sealed finite-headspace systems. Here, a physics-informed pressure-source model is developed for liquid–headspace ANT-EPO chambers by combining first-order oxygen-release kinetics, ideal-gas behavior, Henry-law partitioning, and an experimentally determined efficiency factor. Pressure–time measurements were obtained under controlled conditions at 37, 45, and 50 °C across multiple ANT-EPO concentrations and chamber geometries, with room-temperature measurements included as supporting long-duration datasets. The model captures both transient pressure evolution and the pressure capacity using the same physical formulation across all conditions, achieving a median RMSE of 1.64 % relative to peak pressure and a median peak-pressure mismatch of 0.31 %. Gas–liquid partitioning is described by a dimensionless partition number Π, with all investigated configurations lying in a gas-dominated regime (Π = 0.035–0.083), corresponding to gas-phase fractions of approximately 0.92–0.97. Geometry variation shows that reducing headspace volume increases source pressure capacity within the investigated finite-headspace regime. Model-based pressure-capacity maps and time-to-threshold analysis are then used to define source-level pressure and response-time limits for finite-volume source chambers relevant to pressure-driven microsystem applications. The resulting framework identifies ANT-EPO as a slow, low-pressure chemical source and provides a quantitative basis for screening finite-headspace source configurations against actuator-specific requirements.

Engineering systems increasingly demand multifunctional and energy-efficient integration within constrained volume and energy budgets. One promising solution is the monolithic integration of components and functions to minimize occupied volume and simplify control interfaces. Paraffin-based phase change material (PCM) actuators provide high mechanical work density and can be coupled with thermoelectric generators (TEGs) for multifunctional operation. However, their dynamic response is typically constrained by the intrinsically low thermal conductivity of PCM materials. This work introduces a quasi-monolithic fabrication method for a fully integrated TEG-PCM system combining standard four-layer printed circuit board (PCB) technology and CNC milling. By constructing the system as a quasi-monolithic block, thermal interface materials are considerably reduced, thereby diminishing parasitic thermal resistance and promoting faster heat transport from the TEG to the PCM cavity. The system is fabricated using CNC milling with high depth resolution enabled by an electrical sensing-via structure. Experimental validation shows a 76% improvement in displacement rate (15.03 µm/s) at half the input power (1 W) compared to a conventional hybrid-assembled TEG-PCM actuator system consisting of a commercial TEG and an aluminum PCM container. The exploitation of the PCM as a thermal flux modulator for energy harvesting has been preliminarily investigated; considering the measured 5 K temperature difference sustained during a simulated short “day–night” cycle, an estimated open-circuit voltage of ∼13.5 mV is expected to be retrieved under load-match conditions. The actuator is compatible with PCB-based power management and thermal routing, enabling scalable incorporation into compact microsystems and multifunctional MEMS devices.

Dielectric elastomer actuators (DEAs) are widely used for soft robotics. The required voltages of over 1000 V are usually supplied by amplifiers with batteries or power grids which however have limited operation time or mobility. This problem also exists for other advanced mobile devices such as electroaerodynamic thrusters. This work reports on the development of high-voltage organic photovoltaic mini-modules (HV-OPMs) comprising 5024 individual sub-cells on an area of 3.8 × 3.9 cm². Under 100 klux white LED illumination, an open-circuit voltage (V _OC) of 5534 V and an efficiency of 6.4% is achieved with the photoactive material PM6:GS-ISO whereas with PV-X plus a V _OC of 3970 V and an efficiency of 19.0% is obtained. Furthermore, a soft suction cup based on DEA was built and could successfully be powered with one of these modules. These results show that HV-OPMs are very promising to realize energy autonomy of low-power high-voltage devices.

This study introduces a manufacturing process based on industrial MEMS technology, enabling the production of diverse sensor designs customized for a wide range of absolute pressure measurements. Using monocrystalline silicon as the structural material minimizes thermal stresses and eliminates temperature-dependent semiconductor effects, as silicon functions solely as a mechanical material. Integrating a eutectic bonding process in the sensor fabrication allows for a reliable operation at temperatures up to 350 °C. The capacitive sensor electrodes are enclosed within a silicon-based Faraday cage, ensuring effective shielding against external electrostatic interference. An innovative Through-Silicon Via (TSV) design, sealed using gold–gold (Au-Au) diffusion and gold–silicon (Au-Si) eutectic bonding, further enhances the mechanical and thermal stability of the sensors, even under high-temperature conditions. The unfilled TSV structure mitigates mechanical stress from thermal expansion. The sensors exhibited excellent performance, achieving a linearity of 99.994%, a thermal drift of −0.0164% FS (full scale)/K at full load and 350 °C, and a high sensitivity of 34 fF/kPa. These results highlight the potential of these sensors for high-performance applications across various demanding environments.

Stretchable printed circuit boards (S-PCBs) offer unique advantages over rigid PCBs such as enabling conformability to changing environments and ergonomic designs with increased lifetime under dynamic loads. This study introduces an innovative fabrication method and a cost-effective solution for rapid prototyping S-PCBs using commercially available materials. By utilizing silicone substrates with different levels of stiffness and structured copper sheets for electrical connections, the S-PCBs feature ‘stiff islands’ embedded in a flexible base material. This fabrication method helps alleviate mechanical strain on strain-sensitive components while allowing local deformation of the S-PCB. The proposed fabrication method does therefore enable to integrate surface mount device components into S-PCBs and facilitates complex circuit designs while maintaining stretchability and fatigue resistance. Through material characterization, video strain analysis, as well as quasi-static and cyclic loading tests, this article demonstrates the efficacy of our approach. Based on the experimental results, we provide insights into failure modes and suggest design principles to further enhance the durability of S-PCBs fabricated with our method. We then conclude by presenting a soft wearable S-PCB demonstrator. The S-PCBs fabricated with this method withstood mechanical strains up to 100% and cyclic loads with 30% strain up to 625 cycles. The results are very promising for applications in soft robotics, wearable devices, and soft sensors and actuators. Overall, our study offers a comprehensive toolkit for fast S-PCB prototyping, paving the way for advancements in stretchable electronics with a high degree of complexity and stretchability.

Soft grippers, a rapidly growing subfield of soft robotics, utilize compliant and flexible materials capable of conforming to various shapes. This feature enables them to exert gentle yet, if required, strong gripping forces. In this study, we elaborate on the material selection and fabrication process of gripping fingers based on the dielectric elastomer actuation technique. We study the effects of mixing the silicone elastomer with a silicone thinner on the performance of the actuators. Inspired by nature, where the motion of end-effectors such as soft limbs or fingers is, in many cases, directed by a stiff skeleton, we utilize backbones for translating the planar actuation into a bending motion. Thus, the finger does not need any rigid frame or pre-stretch, as in many other DEA approaches. The idea and function of the backbone strategy are demonstrated by finite element method simulations with COMSOL Multiphysics^® 6.5. The paper describes the full methodology from material choice and characterization, design, and simulation to characterization to enable future developments based on our approach. Finally, we present the performance of these actuators in a gripper demonstrator setup. The developed actuators bend up to 68.3° against gravity, and the gripper fingers hold up to 10.3 g against gravity under an actuation voltage of 8 kV.

Bioinspired and biomimetic soft grippers are rapidly growing fields. They represent an advancement in soft robotics as they emulate the adaptability and flexibility of biological end effectors. A prominent example of a gripping mechanism found in nature is the octopus tentacle, enabling the animal to attach to rough and irregular surfaces. Inspired by the structure and morphology of the tentacles, this study introduces a novel design, fabrication, and characterization method of dielectric elastomer suction cups. To grasp objects, the developed suction cups perform out-of-plane deflections as the suction mechanism. Their attachment mechanism resembles that of their biological counterparts, as they do not require a pre-stretch over a rigid frame or any external hydraulic or pneumatic support to form and hold the dome structure of the suction cups. The realized artificial suction cups demonstrate the capability of generating a negative pressure up to 1.3 kPa in air and grasping and lifting objects with a maximum 58 g weight under an actuation voltage of 6 kV. They also have sensing capabilities to determine whether the grasping was successful without the need of lifting the objects.

In this paper, we present an innovative manufacturing process for the production of capacitive pressure and force sensors with excellent thermal stability for high-temperature applications. The sensors, which are manufactured from a stack of two silicon chips mounted via with gold–silicon (Au-Si) or aluminum–silicon (Al-Si) eutectic bonding, are shielded, miniaturized, and allow an operating temperature of up to 500 °C. Compared to conventional methods, the greatest benefit of the manufacturing process is that different sensor dimensions can be produced in the same batch for a wide measuring range, from mN to kN. The characterization of the realized sensors shows a high linearity and a low temperature drift of 99.992% FS and −0.001% FS/K at 350 °C, as well as a nonlinearity of 0.035% FS and a temperature drift of −0.0027% FS/K at 500 °C.