Thermosensitive wearable sensing technologies with intelligent robotics

The need for advanced multifunctional sensors has increased in the rapidly developing field of robotics and AI-based systems to provide focused functionality, remote security, and human-machine interfaces for efficient control. Recently, H. Lin and co-workers reported at Device that a direct integration of robotics with a self-powered thermosensitive sensor using a robotic hand surpasses the human tactile perception. The need for advanced multifunctional sensors has increased in the rapidly developing field of robotics and AI-based systems to provide focused functionality, remote security, and human-machine interfaces for efficient control. Recently, H. Lin and co-workers reported at Device that a direct integration of robotics with a self-powered thermosensitive sensor using a robotic hand surpasses the human tactile perception. Triboelectric nanosensors (TENS) convert mechanical energy into electrical energy based on contact electrification and electrostatic induction principles, wherein surface charge is produced when two materials come into contact due to friction.1Roy Barman S. Lin Y.-J. Lee K.-M. Pal A. Tiwari N. Lee S. Lin Z.-H. Triboelectric Nanosensor Integrated with Robotic Platform for Self-Powered Detection of Chemical Analytes.ACS Nano. 2023; 17: 2689-2701https://doi.org/10.1021/acsnano.2c10770Crossref Scopus (14) Google Scholar The electricity generated can serve as a power source and for chemical sensing, as the electrical output is affected by the quantity of analytes absorbed on the contact layers of TENS. TENS holds appeal for applications such as in wearable electronics for monitoring physiological signals, and in environmental monitoring, because it can help minimize human exposure to harmful environments.2Wang C. Guo H. Wang P. Li J. Sun Y. Zhang D. An Advanced Strategy to Enhance TENG Output: Reducing Triboelectric Charge Decay.Adv. Mater. 2023; 352209895https://doi.org/10.1002/adma.202209895Crossref Scopus (52) Google Scholar Integrating robotics with self-powered sensors has a wide range of applications emerging from areas such as bionic prosthesis,3Marasco P.D. Hebert J.S. Sensinger J.W. Beckler D.T. Thumser Z.C. Shehata A.W. Williams H.E. Wilson K.R. Neurorobotic fusion of prosthetic touch, kinesthesia, and movement in bionic upper limbs promotes intrinsic brain behaviors.Sci. Robot. 2021; 6eabf3368https://doi.org/10.1126/scirobotics.abf3368Crossref PubMed Scopus (60) Google Scholar virtual/augmented reality, industrial production, and big data training.4Zhu M. Sun Z. Chen T. Lee C. Low cost exoskeleton manipulator using bidirectional triboelectric sensors enhanced multiple degree of freedom sensory system.Nat. Commun. 2021; 12: 2692https://doi.org/10.1038/s41467-021-23020-3Crossref PubMed Scopus (119) Google Scholar,5Sun Z. Zhu M. Shan X. Lee C. Augmented tactile-perception and haptic-feedback rings as human-machine interfaces aiming for immersive interactions.Nat. Commun. 2022; 13: 5224https://doi.org/10.1038/s41467-022-32745-8Crossref PubMed Scopus (174) Google Scholar Some studies have showcased robot-assisted detection of food flavors and organophosphates using enzyme-based electrochemical sensors integrated into commercial gloves and robotic hands.1Roy Barman S. Lin Y.-J. Lee K.-M. Pal A. Tiwari N. Lee S. Lin Z.-H. Triboelectric Nanosensor Integrated with Robotic Platform for Self-Powered Detection of Chemical Analytes.ACS Nano. 2023; 17: 2689-2701https://doi.org/10.1021/acsnano.2c10770Crossref Scopus (14) Google Scholar However, their advancement has been hindered by their continuous power needs and the added complexity and expense of incorporating sensors into glove substrates. These limitations can significantly impact both robustness and wearability, necessitating innovative solutions to unlock their full potential as swift on-site detection tools. In this issue of Device, Lin and co-workers demonstrate a method of combining stretchable substrate (Ecoflex) with NaCl solution to fabricate a stretchable and self-powered sensor that involves integrating thermosensitive triboelectric nanosensors (TS-TENS)6Pal A. Lim K.,C. Chen S.,W. Huang Y.,T. Parashar P. Ganguly A. Chen Y. Fan K.,P. Shen L.,C. Cheng J. Lin Z.,H. Thermosensitive Smart Robotic Self-Powered Sensor for Material Identification.Device. 2024; 2: 100331Google Scholar onto a robotic platform (Figure 1A). This integration enables the recognition of materials through the contact electrification process. With self-powered tactile sensitivity, robotic fingers not only improve user safety but also enhance the accuracy of material identification through a "touch and sense" mechanism. Current robotic sensors and wearable devices rely on traditional power sources such as batteries, which have significant power consumption and short lifespans. The use of batteries in wearable sensors hinders their durability, portability, and safety due to their bulkiness and environmental concerns. Hence, the TS-TENS could enhance sensing capabilities by providing insights into observed phenomena (such as thermal conductivity, ultrasound, and computer vision) and shows the potential to expand the reach of cost-effective automated sensing systems, revolutionizing material identification. The authors explored a flexible sensor featuring a micro-pyramidal morphology on Ecoflex encapsulation infused with NaCl (0.85%) as a conductive electrolyte. This design empowers the sensor to identify materials by their movement of charges in between the aluminum and Ecoflex/NaCl layers, surpassing human tactile perception by utilizing the contact electrification mechanism.6Pal A. Lim K.,C. Chen S.,W. Huang Y.,T. Parashar P. Ganguly A. Chen Y. Fan K.,P. Shen L.,C. Cheng J. Lin Z.,H. Thermosensitive Smart Robotic Self-Powered Sensor for Material Identification.Device. 2024; 2: 100331Google Scholar,7Wang L. Liu W. Yan Z. Wang F. Wang X. Stretchable and Shape-Adaptable Triboelectric Nanogenerator Based on Biocompatible Liquid Electrolyte for Biomechanical Energy Harvesting and Wearable Human–Machine Interaction.Adv. Funct. Mater. 2021; 312007221https://doi.org/10.1002/adfm.202007221Crossref Scopus (116) Google Scholar By integrating the TS-TENS into the architecture of a robotic fingertip, researchers have unlocked the potential for accurate material identification across varying temperature regimes. In this work, the authors have shown a good understanding of the temperature-dependent triboelectric sensing mechanism. They carried out contact electrification experiments and the process was facilitated using a linear motor between a metal and a polymer at different temperatures. This procedure induced triboelectric charging, resulting in the generation of electric charges at the interface between the metal and polymer (Figure 1B). By conducting these experiments across a range of temperatures, the authors systematically analyzed how temperature influences triboelectric charging behavior. To understand the temperature dependent contact electrification mechanism, the authors have conducted the contact-separation electrification experiments across a range of temperatures and measured the open circuit voltage (V vs. T) (Figure 1C) and short circuit current (I vs. T) (Figure 1D) shows the temperature-dependent variations in triboelectric outputs, providing insight into how temperature increases with an increase in voltage that impacts the interaction between the surfaces of the metal and polymer. The authors have also demonstrated an increasing trend with the increment in temperature of the aluminum layer by measuring the output voltage, current density, and power density along the various external load resistance. The sensors fabricated by the authors have shown mechanical robustness through the execution of 500 cycles encompassing folding, twisting, and bending as well as the stability in its performance for a longer period without losing the stability and performance capabilities. Additionally, the authors explore how TS-TENS's sensing capability is enhanced by a small temperature increase and explains how the sensing capability is reliant on temperature using Kelvin Probe Force Microscopy (KPFM), an important tool to understand the contact separation mechanism via change in surface potential of the various materials (Figure 1E). KPFM techniques have been utilized to demonstrate complex interplay of material behaviors elucidated by temperature-dependent surface potential analysis and have revealed intriguing discrepancies among the various materials (such as metals to polymers) as temperature variables fluctuated. This tool plays a vital role in depicting the facet of the sensor's operation to unravel the underlying mechanisms governing the TS-TENS sensing capabilities. By connecting fundamental scientific knowledge and real-world applications, researchers have enhanced the potential for advancements in healthcare, environmental monitoring, robotics, IoT devices, and human-machine interfaces. The authors have demonstrated the practical effectiveness of the integrated triboelectric sensing model (TS-TENS) in distinguishing between different materials and detecting temperature changes. This state-of-the-art initiative resulted in the development of a technologically advanced robotic hand with tactile perception capabilities surpassing those of humans. This visual representation exemplifies the integrated system's capacity to recognize various materials, including metals, biomaterials, and polymers. The sensors of the robotic hand, which are a vital component of this system, directly interacted with a variety of materials across different temperature settings, eliminating the need for complex procedures or preparatory steps. Finally, the study demonstrates the robotic-hand-based sensor's capability for identifying multiple materials across varying temperatures. The authors employed computational learning techniques, enhancing material identification through temperature-sensitive triboelectric nanogenerators (TS-TENSs) with machine learning where further research can push the limits of their devices. This includes the development of robotic hand sensors that were actively involved in direct contact and separation with various materials across different temperature settings, eliminating the need for complex procedures. This interaction resulted in a continuous stream of voltage output signals, facilitating material sensing without elaborate setups to further improve the sensor's ability to identify materials. Subsequently, the collected sensing data underwent processing through machine learning algorithms for analysis and classification. Importantly, even a slight increase in the temperature range results in a significant improvement in the efficacy of material identification, leading to an accuracy rate that rises from 94.44% to 88.88% to an impressive 97.22% and 100% for the SVC and random forest models, respectively. This illustrates the potential of this research in the realms of prosthetics and intelligent robotic applications moving forward. The study by Lin and co-workers advances the integration of thermosensitive triboelectric nanosensors with intelligent robotics and points out crucial areas where further investigation may improve the performance and potential of their device. Specifically, enhancing sensing efficiencies, particularly for various thermosensitive multi-material samples, could broaden the potential applications of the system. Lastly, demonstrating the real-time temperature sensing ability of the robotic-hand-based TS-TENS could provide insights into the practical usability of the system. The authors acknowledge the European Research Executive Agency (REA) and the Marie Skłodowska-Curie Actions (MSCA) Postdoctoral Fellowships (Call: HORIZON-MSCA-2021-PF-01; Project number: 101067060). The authors declare no competing interests. Revolutionizing flexible electronics with liquid metal innovationsLin et al.DeviceMay 17, 2024In BriefLiquid metals have recently made substantial breakthroughs in flexible electronics. This perspective elaborates on liquid metals in flexible electronic devices. Here, Zuankai Wang and co-workers summarize the latest innovations of flexible, liquid-metal-based electronic devices in fabrication methods and applications and evaluate the present status and future outlook. This perspective aims to identify the challenges and opportunities of liquid metals in flexible electronic devices and provide insights into the future research direction of the field. Full-Text PDF