Triboelectric nanogenerators (TENGs) are fast emerging as promising and potential energy harvesters. However, the performance of the polymer-based TENGs needs to be enhanced for haptic and wearable applications. In this work, we have designed and developed polydimethylsiloxane (PDMS) and multi-wall carbon nanotubes (MWCNT) based TENG for haptic applications. The unique electrical properties of the human body, which make it a suitable triboelectric material, were a critical factor in our design. The incorporation of MWCNTs enhanced the electrical properties of the nanocomposite, thereby increasing the performance of the TENG. To demonstrate the performance of the TENG under variable contact tapping forces and frequencies, the as-fabricated films were tested in vertical contact separation and single electrode modes. The TENG exhibited an open circuit output voltage of ~249 V, a short circuit current of ~28.03 μA, and a power density of 2.81 W/m ² at a matching load of 5.5 MΩ. The TENG exhibited an excellent, stable electrical performance for haptic applications. The TENG’s excellent performance was validated by the illumination of 30 blue and 120 red LEDs. Additionally, it was employed to power portable electronic devices. Therefore, these flexible and wearable TENGs with high performance are highly desirable for haptic applications.

Fused filament fabrication (FFF)-based 3D-printing technology for thermoplastics is known to be a versatile process that enables wide-ranging structural improvements (rheological, mechanical and electrical properties) of polymer-based materials for energy harvesting applications. In this study, we report a 3D-printed poly(vinylidene difluoride, PVDF)-based nanogenerator (3D-HTPENG) that operates in a hybrid synergistic mechanism incorporating predominantly triboelectric effect (electrostatic induction and friction-based charge generation) with minor piezo-electric contribution. Under vertical contact-separation operation, the device delivers a peak open-circuit voltage of ~260 V and a short-circuit current of ~16 μA, corresponding to a maximum power density of ~690 μW/cm². Surface charging and electrostatic induction under mechanical loading serve as the primary source of voltage generation, while the piezoelectric components (²- and ϒ-phases) contributes secondary outputs, particularly during low-force deformations. AFM and FTIR analysis confirmed the presence of polar ²- and ϒ-phases in the printed films, with crystallization behavior influenced by film thicknesses (0.1-0.4 mm). The system demonstrates excellent short-term stability (>5000 cycles), and exhibits practical utility in tactile-integrated sensing, wearable electronics, and soft robotic segments. Our findings suggest that PVDF-based 3D-printed devices can function as high-output triboelectric nanogenerators with supplementary piezoelectric effects. Owing to stronger triboelectric output, the 3D-HPTENG is also an excellent multidirectional force sensing device alternative to conventional resistive sensors that can be utilized as tactile sensors and arrays for applications in wearable technologies, soft robotics and internet-of-things (IoTs).

This paper uses a very effective way for surface modification of thermoplastic polymers during moulding. It is based on a grafting reaction between a thin layer of a functional polymer, deposited on a substrate in advance, and a polymer melt. In this paper, a glycol-modified polyethylene terephthalate (PETG) that was brought in contact with a polyethyleneimine layer during fused filament fabrication is investigated. The focus of this paper is the investigation of the reaction product. Grafting was realised by the formation of stable amide bonds by amidation of ester groups in the main chain of a PETG. XPS investigations revealed that the conversion of amino groups was very high, the distribution was even, and the quantity of amino groups per polyester surface area was still very high. The surface properties of the produced polyester part were mainly characterised by polyethyleneimine. The grafting was able to resist several cycles of extraction in alkaline solutions. The stability was only limited by saponification of the polyester. The degree of surface modification was dependent on the molar mass of polyethyleneimine. This could be rationalised, because grafting only occurred with the one polyethyleneimine molecule that is in close vicinity to the polyester surface when both components come in contact. Fused deposition modelling was chosen as the model process with control over each processing step. However, any other moulding process may be applied, particularly injection moulding for mass production.