2D material-based sensing technology innovation roadmap for biomedical applications

Diversiform sensors and sensing systems driven by triboelectric and piezoelectric nanogenerators

Although research on triboelectric nanogenerators (TENGs) has evolved rapidly, comprehensive data-driven studies remain limited. This study addresses this gap by conducting a scientometric analysis integrated with unsupervised topic modeling. Utilizing 8556 Scopus documents (1999–2024), we present a quantitative overview of the TENG research field. The analysis revealed exponential growth in publications, particularly after 2018. The TENG research landscape has been geographically led by China, the U.S.A. and South Korea, featuring a collaborative network centered on influential authors such as Wang, Z.L. and characterized by a highly modular author collaboration structure with comparatively weaker cross-cluster integration at the researcher level. Separate co-occurrence network analyses of commonly used materials and application terms confirmed that TENG studies primarily emphasize energy harvesting and self-powered sensors, with polydimethylsiloxane (PDMS) emerging as the most dominant material. Unsupervised topic modeling further identified six core thematic structures, including wearable electronics, sensing technologies, low-power energy harvesting, output enhancement, material innovation, and large-scale power generation. The findings of this study indicate a clear shift in research emphasis from low-power devices to large-scale energy production applications. Furthermore, the growing interest in biomedical applications and data-driven signal processing highlights important directions for future TENG development and deployment.

Triboelectric nanogenerator for healthcare and biomedical applications

Flexible and stretchable triboelectric nanogenerators (TENGs) have been rapidly advanced owing to the demand for portable and wearable electronic devices that can work under universal or motional circumstances. While versatile materials can be applied in a TENG as dielectric materials, flexible and cost-effective electrodes are crucially important for the output performance of TENGs. Herein, we developed a poly(vinyl alcohol) (PVA) hydrogel TENG doped with a novel two-dimensional material, graphitic carbon nitride (g-C3N4), which could act as both a cost-effective flexible electrode and a positive dielectric for TENG with different morphologies. The measured peak-to-peak open-circuit voltage of the TENG reached 80 V at a dopant concentration of 2.7 wt % in single-electrode mode, which is far higher than that of the pristine PVA hydrogel TENG. As a demonstration of the application, the g-C3N4/PVA hydrogel TENG can be adopted as electronic skin to monitor the movement of the human body. Low-frequency mechanical energy-harvesting devices in different morphologies including discoid flake shape, tube shape, and spiral shape in the single-electrode mode or contact-separation mode have been designed, fabricated, and evaluated. All of these merits of the proposed hydrogel TENG after doping two-dimensional (2D) material g-C3N4 have demonstrated their promising potential for versatile applications in biomechanical energy harvesting and self-powered sensing.

The Graphene Flagship—A Giant European Research Project.

With the rise of graphene, there is growing attention on two-dimensional (2D) materials in the physical science community during the last decade. Most studies to date focus on the rich set of their superior electrical, optical, catalytic and electrochemical properties and highlight the encouraging opportunities for developing next generation electronics, optoelectronics, catalysis, and energy storage technologies. On the contrary, the biomedicine community has barely recognized the potential of these materials other than graphene. There are very limited published studies on these materials’ biological effects and biomedical applications. Here, we present a brief overview of 2D materials and discuss their potential for biomedical applications in hope of raising biomedical researchers’ awareness of the great opportunities associated with these materials. We first discuss the emergence of 2D materials and review two most important prerequisites for 2D materials’ biomedical applications, synthesis and biocompatibility. We then categorize the existing studies on 2D materials’ biomedical applications into biosensing, drug/gene delivery, antimicrobial, bioimaging and multimode therapeutic applications. We would put special emphasis on the great flexibility of various rational combinations of 2D material superior properties for the design and construction of assorted forms of reagents or devices with highly effective simultaneous diagnostic and therapeutic functions (or theranostics functions). At last, the newly emerging 2D black phosphorous with very rare and interesting properties is introduced as the next promising and important 2D materials to study in the upcoming years.

Biopolymers have attracted considerable attention in various biomedical applications. Among them, cellulose as sustainable and renewable biomass has shown potential efficacy. With the advancement in nanotechnology, a wide range of nanostructured materials have surfaced with the potential to offer substantial biomedical applications. . The progress of cellulose at the nanoscale regime (nanocelluloses) with diverse forms like cellulose nanocrystals, nanofibres and bacterial nanocellulose) has imparted remarkable properties like high aspect-ratio and high mechanical strength, and biocompatibility. The amalgamation of nanocellulose together with magnetic nanoparticles (MNC) could be explored for a synergistic effect. In this review, a brief introduction of nano cellulose , magnetic nanoparticles and the synergistic effect of MNC is described. Further, the review sheds light on the recent studies based on MNCs with their potential in the biomedical area. Finally, the review is concluded by citing the remarkable value of MNC with their futuristic applications in other fields like friction layers for triboelectric nanogenerator (TENG), energy production, hydrogen splitting, and wearable electronics.

Emergent 2D materials beyond graphene: Plausible role in biomedical applications

Recently, there has been an increasing consumption of fossil fuels such as oil and natural gas in both industrial production and daily life. This high demand for non-renewable energy sources has prompted researchers to investigate sustainable and renewable energy alternatives. The development and production of nanogenerators provide a promising solution to address the energy crisis. Triboelectric nanogenerators, in particular, have attracted significant attention due to their portability, stability, high energy conversion efficiency, and compatibility with a wide range of materials. Triboelectric nanogenerators (TENGs) have many potential applications in various fields, such as artificial intelligence (AI) and the Internet of Things (IoT). Additionally, by virtue of their remarkable physical and chemical properties, two-dimensional (2D) materials, such as graphene, transition metal dichalcogenides (TMDs), hexagonal boron nitride (h-BN), MXenes, and layered double hydroxides (LDHs), have played a crucial role in the advancement of TENGs. This review summarizes recent research progress on TENGs based on 2D materials, from materials to their practical applications, and provides suggestions and prospects for future research.

Two-dimensional (2D) materials beyond graphene in cancer drug delivery, photothermal and photodynamic therapy, recent advances and challenges ahead: A review

Through previous research, the excellent biocompatibility and bioactivity of calcium silicate were proven with the wide use in biomedical application. In this work, calcium silicate was synthesized from tetraethylorthosilicate (TEOS) and calcium nitrate tetrahydrate with calcium oxide: silicon dioxide (CaO: SiO2) ratio of 30:70 using sol-gel method. Chemical composition of CaO and SiO2 were analyzed using X-ray diffraction (XRD) and X-ray fluorescent (XRF). Magnetic Nanoparticles (MNPs) are gaining interest in all biomedical related application. However the usage of MNPs can’t be used directly and needed coating layer to improve the dispersion stability, biocompatibility and provide functionality. MNPs materials used in this research are maghemite (γ-Fe2O3). Maghemite was synthesized from ferrous chloride (FeCl3) and ferric chloride (FeCl2) with ratio FeCl3 to FeCl2 2:1 using sol gel method. Through this research, the potential of new coating materials which is calcium silicate to coat on maghemite while maintained the magnetic properties were studied and analyzed using VSM, XRD and XRF.Through previous research, the excellent biocompatibility and bioactivity of calcium silicate were proven with the wide use in biomedical application. In this work, calcium silicate was synthesized from tetraethylorthosilicate (TEOS) and calcium nitrate tetrahydrate with calcium oxide: silicon dioxide (CaO: SiO2) ratio of 30:70 using sol-gel method. Chemical composition of CaO and SiO2 were analyzed using X-ray diffraction (XRD) and X-ray fluorescent (XRF). Magnetic Nanoparticles (MNPs) are gaining interest in all biomedical related application. However the usage of MNPs can’t be used directly and needed coating layer to improve the dispersion stability, biocompatibility and provide functionality. MNPs materials used in this research are maghemite (γ-Fe2O3). Maghemite was synthesized from ferrous chloride (FeCl3) and ferric chloride (FeCl2) with ratio FeCl3 to FeCl2 2:1 using sol gel method. Through this research, the potential of new coating materials which is calcium silicate to coat on maghemite while ...

Triboelectric nanogenerators (TENGs) have attracted many researchers’ attention with their remarkable potential despite the fact that the practical implementation requires further improvement in their electric performance. In this work, a novel graphene phase two-dimension material, graphitic carbon nitride (g-C3N4), was employed for the development of a TENG material with enhanced features. An electrospun nanofibrous PA66 membrane doped with g-C3N4 was fabricated as a multifunctional TENG for harvesting different kinds of mechanical energy and detecting human motions. By utilizing the innovative 2D material in PA66 solution for electrospinning, the as-made TENG showed a two times enhancement in electrical performance as compared to the control device, and also had the advantages of lightweight, softness, high porosity, and rugged interface properties. The assembled TENG with 4 cm2 could light up 40 light-emitting diodes by gentle hand clapping and power electronic watches or calculators with charging capacitors. At a given impact force of 40 N and 3 Hz, the as-made TENG can generate an open-circuit voltage of 80 V, short current of ±3 µA, charge transfer of 50 nC, and a maximum power density of 45 mW/m2 at a load resistance of 500 MΩ. The UV light sensitivity of TENG was also improved via g-C3N4 doping, showing that charge transfer is very sensitive with a two times enhancement with dopant. For the demonstration of applications, the g-C3N4 doped TENG was fabricated into an energy flag to scavenge wind energy and sensor devices for detecting human motions.

The rapid advancement of triboelectric nanogenerators (TENGs) has introduced a transformative approach to energy harvesting and self-powered sensing in recent years. Nonetheless, the untapped potential of TENGs in practical scenarios necessitates multiple strategies like material selections and structure designs to enhance their output performance. Given the various superior properties, MXenes, a kind of novel 2D materials, have demonstrated great promise in enhancing TENG functionality. Here, this review comprehensively delineates the advantages of incorporating MXenes into TENGs, majoring in six pivotal aspects. First, an overview of TENGs is provided, stating their theoretical foundations, working modes, material considerations, and prevailing challenges. Additionally, the structural characteristics, fabrication methodologies, and family of MXenes, charting their developmental trajectory are highlighted. The selection of MXenes as various functional layers (negative and positive triboelectric layer, electrode layer) while designing TENGs is briefed. Furthermore, the distinctive advantages of MXene-based TENGs and their applications are emphasized. Last, the existing challenges are highlighted, and the future developing directions of MXene-based TENGs are forecasted.

Nanogenerators is the growing technology that facilitates self-powered systems, sensors, and flexible and portable electronics in the thriving era of internet of things (IoT). Since the first invention of the triboelectric nanogenerators (TENGs) in 2012, it has become one of the most important inventions in energy harvesting technologies. In this paper, a brief review on the recent progress of energy harvesting research based on TENGs technology is discussed. Basic working modes of the TENG are discussed in detail and the general procedure to synthesize, measure, and characterize a nanogenerator is presented in a direct structure. The triboelectric material choices are extremely important for TENGs since the triboelectric effects of the materials are fundamental for TENGs. The materials used as triboelectric layers are varied from polymers, metals, and inorganic materials with the commonly used materials are dielectric polymers such as PTFE, PVDF, PDMS, nylon, and Kapton. Recently, two-dimensional (2D) materials have been widely reported as candidate materials for TENGs. Graphene, the most attractive 2D materials exhibits an excellent electrical property, great flexibility, and a high surface-to-volume ratio. Owing to the very low thickness of the atomic unit, a stacking graphene structure can be also made to form a very thin and miniature TENGs device. The major applications of the graphene as active materials for TENGs as a sustainable energy harvester are presented, following which structural designs and materials optimization for output performance improvement of the graphene-based TENGs are summarized. Finally, the future directions and perspectives of the graphene-based TENGs are outlined. The graphene-based TENGs is not only a sustainable micro-power source for small devices, but also serves as a potential macro-scale generator of power from blue energy in the future.

In the domains of wearable electronics, robotics, and the Internet of Things, there is a demand for devices with low power consumption and the capability of multiplex sensing, memory, and learning. Triboelectric nanogenerators (TENGs) offer remarkable versatility in this regard, particularly when integrated with synaptic transistors that mimic biological synapses. However, conventional TENGs, generating only two spikes per cycle, have limitations when used in synaptic devices requiring repetitive high-frequency gating signals to perform various synaptic plasticity functions. Herein, a multi-layered micropatterned TENG (M-TENG) consisting of a polydimethylsiloxane (PDMS) film and a composite film that includes 1H,1H,2H,2H-perfluorooctyltrichlorosilane/BaTiO3 /PDMS are proposed. The M-TENG generates multiple spikes from a single touch by utilizing separate triboelectric charges at the multiple friction layers, along with a contact/separation delay achieved by distinct spacers between layers. This configuration allows the maximum triboelectric output charge of M-TENG to reach up to 7.52 nC, compared to 3.69 nC for a single-layered TENG. Furthermore, by integrating M-TENGs with an organic electrochemical transistor, the spike number multiplication property of M-TENGs is leveraged to demonstrate an artificial synaptic device with low energy consumption. As a proof-of-concept application, a robotic hand is operated through continuous memory training under repeated stimulations, successfully emulating long-term plasticity.