A hybrid sensory feedback system for thermal nociceptive warning and protection in prosthetic hand

Background

Advanced prosthetic hands may embed nanosensors and microelectronics in their cosmetic skin. Heat influx may cause damage to these delicate structures. Protecting the integrity of the prosthetic hand becomes critical and necessary to ensure sustainable function. This study aims to mimic the sensorimotor control strategy of the human hand in perceiving nociceptive stimuli and triggering self-protective mechanisms and to investigate how similar neuromorphic mechanisms implemented in prosthetic hand can allow amputees to both volitionally release a hot object upon a nociceptive warning and achieve reinforced release via a bionic withdrawal reflex.

Methods

A steady-state temperature prediction algorithm was proposed to shorten the long response time of a thermosensitive temperature sensor. A hybrid sensory strategy for transmitting force and a nociceptive temperature warning using transcutaneous electrical nerve stimulation based on evoked tactile sensations was designed to reconstruct the nociceptive sensory loop for amputees. A bionic withdrawal reflex using neuromorphic muscle control technology was used so that the prosthetic hand reflexively opened when a harmful temperature was detected. Four able-bodied subjects and two forearm amputees randomly grasped a tube at the different temperatures based on these strategies.

Results

The average prediction error of temperature prediction algorithm was 8.30 ± 6.00%. The average success rate of six subjects in perceiving force and nociceptive temperature warnings was 86.90 and 94.30%, respectively. Under the reinforcement control mode in Test 2, the median reaction time of all subjects was 1.39 s, which was significantly faster than the median reaction time of 1.93 s in Test 1, in which two able-bodied subjects and two amputees participated. Results demonstrated the effectiveness of the integration of nociceptive sensory strategy and withdrawal reflex control strategy in a closed loop and also showed that amputees restored the warning of nociceptive sensation while also being able to withdraw from thermal danger through both voluntary and reflexive protection.

Conclusion

This study demonstrated that it is feasible to restore the sensorimotor ability of amputees to warn and react against thermal nociceptive stimuli. Results further showed that the voluntary release and withdrawal reflex can work together to reinforce heat protection. Nevertheless, fusing voluntary and reflex functions for prosthetic performance in activities of daily living awaits a more cogent strategy in sensorimotor control.

Passive Filler-Loaded Silicon Oxycarbide Coating on Nickle Alloy with High Thermal Shocking Behavior and Oxidation Resistance

Polymer-derived ceramic (PDC) coatings of considerable thickness can offer promising protection for metallic and superalloy substrates against oxidation and corrosion, yet the preparation remains challenging. Here, a SiOC/Al₂O₃/YSZ coating was prepared on a nickel alloy with a spraying method using Al₂O₃ and yttria-stabilized zirconia (YSZ) as passive fillers. The thickness can reach up to 97 μm with the optimal mass fraction and particle sizes of the passive fillers. A small or isolated SiOC phase is formed in the coating, which can effectively alleviate the shrinkage and cracking during the pyrolysis. The SiOC/Al₂O₃/YSZ coating exhibits low thermal conductivity and high bonding strength with the substrate. Moreover, the coating shows good thermal shock resistance between 800 °C-room temperature cycles and oxidation resistance at 1000 °C for 36 h. This work provides an effective guide for the design of thick PDC coatings to further promote their application in the thermal protective field.

Design of the Thermal Restructured Carbon-Inorganic Composite Aerogel for Efficient Thermal Protection of Aero-Engines

The heat insulation ability and thermal stability of thermal protection materials play extremely important role in the thermal protection of aero-engines under high temperature. Herein, we design the carbon-SiO₂-Al₂O₃ (CSA) composite aerogel through thermochemical restructuring from the phenol-formaldehyde resin-SiO₂-Al₂O₃ (PSA) composite aerogel. This thermochemical restructured aerogel not only shows better adhesion property under room temperature but also possesses higher thermal stability and desirable heat insulation ability under high temperature. Taking the PSA-0.5 composite aerogel as an example, the compressive strain-stress test unveils that it can be compressed by 66% without catastrophic collapse, which is beneficial for the adhesion with the metallic matrix. Meanwhile, the transmission electron microscopy and scanning electron microscopy images exhibit the unbroken three-dimensional structure for the CSA-0.5 composite aerogel, which confirmed the structural stability of the composite aerogel after thermochemical restructuring. The thermal cycle test indicates that the weight loss of the CSA-0.5 composite aerogel is only ca. 8%, firmly confirming its thermal stability. Importantly, the thermal conductivity of the CSA-0.5 composite aerogel ranges from 0.024 to 0.083 W m^-1 K^-1, indicating the superior performance of heat insulation. Moreover, the numerical simulation is carried out to validate the thermal protection effect of the CSA-0.5 composite aerogel as a thermal protection layer. Together with laminated cooling, it could enhance the surface cooling effectiveness of the metallic matrix to above 0.8. Briefly, this work paves a new pathway for efficient thermal protection materials of aero-engines via the rational design of the thermochemical restructured composite aerogel under the guidance of ANSYS numerical simulations.

Interventional Palliation of Painful Extraspinal Musculoskeletal Metastases

The musculoskeletal system is commonly involved by metastases, and skeletal-related events such as intractable pain due to direct osseous tumor involvement, pathologic fracture, and neurologic deficits as a result of nerve compression often adversely affect patient's quality of life. There have been substantial advances in percutaneous minimally invasive musculoskeletal oncologic interventions for the management of patients with musculoskeletal metastases including thermal ablations, cementation with or without osseous reinforcement via implants, osteosynthesis, neurolysis, and palliative injections which are progressively incorporated in clinical practice. These interventions are performed, in conjunction with or supplemented by adjuvant radiation therapy, systemic therapy, surgery, or analgesics, to achieve durable pain palliation, local tumor control, or cure. This article reviews minimally invasive percutaneous image-guided musculoskeletal oncologic interventions for the management of patients with extraspinal musculoskeletal metastases.

Multifunctional Ceramic Composite System for Simultaneous Thermal Protection and Electromagnetic Interference Shielding for Carbon Fiber-Reinforced Polymer Composites

Achieving a high electrical conductivity while maintaining a good thermal insulation is often contradictory in the material design for the goal of simultaneous thermal protection and electromagnetic interference shielding. The reason is that materials with a high electrical conductivity often pertain a high thermal conductivity. To address this challenge, this study reports a multifunctional ceramic composite system for carbon fiber-reinforced polymer composites. The fabricated multifunctional ceramic composite system has a multilayer structure. The polymer-derived SiCN ceramic reinforced with yttria-stabilized zirconia fibers serves as the thermal protection and impedance-matching layer, while the yttria-stabilized zirconia fiber-reinforced SiCN ceramic with carbon nanotubes provides the electromagnetic interference shielding. The thermal conductance of the multilayered ceramic composite is about 22.5% lower compared to that of the carbon fiber-reinforced polymer composites. The thermal insulation test during the steady-state condition shows that the hybrid composite can be used up to 300 °C while keeping the temperature reaching the surface of carbon fiber-reinforced polymer composites at around 167.8 °C. The flame test was used to characterize the thermal protection capability under transient conditions. The hybrid composite showed temperature differences of 72.9 and 280.7 °C during the low- and high-temperature settings, respectively. The average total shielding efficiency per thickness of the fabricated four-layered ceramic composite system was 21.45 dB/mm, which showed a high reflection-dominant electromagnetic interference shielding. The average total shielding efficiency per thickness of the eight-layered composite system was 16.57 dB/mm, revealing a high absorption-dominant electromagnetic interference shielding. Typical carbon fiber-reinforced polymer composites reveal a reflection-dominant electromagnetic interference shielding. The electrons can freely move in the percolated carbon nanotubes within the inner layers of the composite material, which provide the improved electromagnetic interference shielding ability. The movement of electrons was impeded by the top and bottom layers whose thermal conduction relies on the lattice vibrations, resulting in a satisfactory thermal insulation of the composite materials and impedance matching with the free space. Results of this study showed that materials with a good thermal insulation and electromagnetic interference shielding can be obtained simultaneously by confining the electron movement inside the materials and refraining their movement at the skin surface.

3D Lamellar Structure of Biomass-Based Porous Carbon Derived from Towel Gourd toward Phase Change Composites with Thermal Management and Protection

The practical application of shape-stable phase change composites (PCCs) is beneficial to thermal energy management and energy conservation due to their superior properties. A shape-stable PCC was fabricated by incorporating poly(ethylene glycol) (PEG) with biomass-based porous carbon that was produced via freeze-drying and carbonization using a low-cost and environmentally friendly fresh towel gourd. The towel gourd derived porous carbon with the characteristics of porosity, unique three-dimensional (3D) lamellar structure, and high specific surface area allowed a high encapsulation capacity (up to 94.5 wt %) for PEG. Structural morphologies, as well as the properties of latent heat storage, thermal reliability, thermal energy management, and thermal protection ability of the fabricated shape-stable PCC, were investigated. The micromorphologies revealed that PEG molecular chains were arranged in a 3D lamellar tissue structure. The shape-stable PCC demonstrated excellent thermal reliability and a high melting latent heat of ∼164.3 J/g. The analysis of infrared thermal images indicated that the shape-stable PCC exhibited remarkable strengths in thermal energy management. The result of the thermal insulation simulation experiment proved that the shape-stable PCC had superior thermal protection ability. This study provided an innovative strategy for the design and development of shape-stable PCCs for great potential in heat-insulating protective textiles, solar thermal energy storage, energy-saving buildings, and infrared stealth of military targets.

Short-Chain Modified SiO2 with High Absorption of Organic PCM for Thermal Protection

Organic phase change materials (PCMs) have great potential in thermal protection applications but they suffer from high volumetric change and easy leakage, which require "leak-proof" packaging materials with low thermal conductivity. Herein, we successfully modify SiO2 through a simple 2-step method consisting of n-hexane activation followed by short-chain alkane silanization. The modified SiO2 (M-SiO2) exhibits superior hydrophobic property while maintaining the intrinsic high porosity of SiO2. The surface modification significantly improves the absorption rate of RT60 in SiO2 by 38%. The M-SiO2/RT60 composite shows high latent heat of 180 J·g-1, low thermal conductivity of 0.178 W·m-1·K-1, and great heat capacity behavior in a high-power thermal circuit with low penetrated heating flow. Our results provide a simple approach for preparing hydrophobic SiO2 with high absorption of organic PCM for thermal protection applications.

Advanced Radar Absorbing Ceramic-Based Materials for Multifunctional Applications in Space Environment

In this review, some results of the experimental activity carried out by the authors on advanced composite materials for space applications are reported. Composites are widely employed in the aerospace industry thanks to their lightweight and advanced thermo-mechanical and electrical properties. A critical issue to tackle using engineered materials for space activities is providing two or more specific functionalities by means of single items/components. In this scenario, carbon-based composites are believed to be ideal candidates for the forthcoming development of aerospace research and space missions, since a widespread variety of multi-functional structures are allowed by employing these materials. The research results described here suggest that hybrid ceramic/polymeric structures could be employed as spacecraft-specific subsystems in order to ensure extreme temperature withstanding and electromagnetic shielding behavior simultaneously. The morphological and thermo-mechanical analysis of carbon/carbon (C/C) three-dimensional (3D) shell prototypes is reported; then, the microwave characterization of multilayered carbon-filled micro-/nano-composite panels is described. Finally, the possibility of combining the C/C bulk with a carbon-reinforced skin in a synergic arrangement is discussed, with the aid of numerical and experimental analyses.

Highly Electrically Conducting Glass-Graphene Nanoplatelets Hybrid Coatings

Hybrid coatings consisting of a heat resistant Y2O3-Al2O3-SiO2 (YAS) glass containing 2.3 wt % of graphene nanoplatelets (GNPs) were developed by flame spraying homogeneous ceramic powders-GNP granules. Around 40% of the GNPs survived the high spraying temperatures and were distributed along the splat-interfaces, forming a percolated network. These YAS-GNP coatings are potentially interesting in thermal protection systems and electromagnetic interference shields for aerospace applications; therefore silicon carbide (SiC) materials at the forefront of those applications were employed as substrates. Whereas the YAS coatings are nonconductive, the YAS-GNP coatings showed in-plane electrical conductivity (∼10(2) S·m(-1)) for which a low percolation limit (below 3.6 vol %) is inferred. Indentation tests revealed the formation of a highly damaged indentation zone showing multiple shear displacements between adjacent splats probably favored by the graphene sheets location. The indentation radial cracks typically found in brittle glass coatings are not detected in the hybrid coatings that are also more compliant.

Important Parameter Groups in Thermal Protection of Polymers

The problem of thermal protection is explored for two idiosyncratic reactive systems, namely a sacrificial heat-sink material and an intumescent system where a dynamically evolving insulation layer is produced from an initially thin coating. Relatively simple mathematical models of both systems are proposed that encompass the important physical characteristics of each situation and these models are analysed using a mixture of numerical and analytical techniques. Important dimensionless parameter groups are identified and domains of parameter space where thermal performance is particularly good- or particularly bad- are identified.

Cost-effective application of thermal protection on LPG road transport tanks for risk reduction due to hot BLEVE incidents

A simplified risk and cost-benefit analysis is presented for the application of thermal protection (TP) on propane and LPG highway tanker trucks operating in North America. A risk analysis is performed to determine the benefits of risk reduction by TP, relative to the costs of applying and maintaining TP on a tanker truck. The results show that TP is cost effective if the tanker truck spends enough time (or travels enough distance) in areas of moderate or high population density. The analysis is very sensitive to a number of inputs, including: (i) value of life, (ii) hot boiling liquid expanding vapor explosion frequency, (iii) public exposure to severe hazards, and (iv) life cost of TP. With this simplified analysis, it is possible to generate tanker truck exposure times to the public that justify the application of TP based on cost and benefit considerations.