Abstract

As the world of electronics quickly expands, emerging materials and novel electronic devices nurture the expansion of more-than-Moore technologies, with special developments made in areas such as flexible electronics and artificial electronic skins (e-skins). Such developments are promising when it comes to deliver natural touch sensation to prosthetic users, or next-generation robotic applications. Nevertheless, replicating the human skin is not an easy feat as it contains thousands of specialized receptors that instantly responding to pressures, vibrations, temperature and noxious cues. In this context, artificial skins are systems that replicate the sense of touch by means of soft electronic sensors. These require flexibility in its nature, to conform to rigid parts such as robotic arms, while meeting requirements such as the miniaturization and densification of devices over large areas. Evidently, processing artificial skins packed with such sensing arrays comes at with high power consumption and high computational cost. To this end, emerging concepts such as neuromorphic computing carry great promise, as they are capable of providing event-driven, parallel and energy efficient computation. Following such motivations, this thesis focusses on the coalition of flexible nanomaterial-based electronics and emerging neuromorphic devices, for the development of building blocks of next generation neuromorphic electronic skins. The demonstrated flexible devices consist in highly crystalline inorganic nanowires (NWs) with high aspect ratio (>1000), enabling superior mechanical properties. The functional NWs are deployed at precise locations over flexible substrates through dielectrophoretic (DEP) solution processable assembly. The versatility of the setup is shown through the assembly of different materials such as Vanadium Pentoxide NWs (V2O5) and Zinc Oxide (ZnO) over large areas. The aligned V2O5 NWs are used as active channel for highly sensitive thermal sensors, fabricated through the novel high-resolution electrohydrodynamic (EHD) jet printing. The ultra-small thermoreceptor exhibits high sensitivity (-1.1 ± 0.3%ºC-1), fast response (≈1s) and exceptional stability. The device capabilities are demonstrated through the reflex to thermal pain on a robotic arm.

Moreover, DEP assembled ZnO nanowires and transfer printed high-mobility Si nanoribbons (Si NRs) are used as active channel for flexible top-gated transistors. Given the high mobility of doped silicon NRs, high-performance printed n- and p-type FETs are developed through EHD jet printing of metal and encapsulation layers. The printed Si NR transistors show effective peak mobilities of 15 cm2/Vs (n-channel) and 5 cm2/Vs (p-channel) at low 1 V drain voltage, with good stability after 10000 bending cycles at different bending radius (40, 25, and 15 mm). Lastly, neuron-like transistors are developed using the DEP aligned ZnO NWs. The device incorporates a floating gate (FG) which capacitively couples with multiple top-gates. Such coupling enables voltage-mode summation at the FG, where more than one parallel input modulates the output of the device. Given the observed charge trapping and multiple input configuration, the device exhibits spatiotemporal summation of spike-based inputs, demonstrating the efficacy of the developed neural FET for synaptic applications.

Publications

Neto, J., Dahiya, A.S. & Dahiya, R. Multi-gate neuron-like transistors based on ensembles of aligned nanowires on flexible substrates. Nano Convergence 12, 2 (2025). https://doi.org/10.1186/s40580-024-00472-z

Neto, J., Chirila, R., Dahiya, A. S., Christou, A., Shakthivel, D., & Dahiya, R. (2022). Skin‐inspired thermoreceptors‐based electronic skin for biomimicking thermal pain reflexes. Advanced Science, 9(27), 2201525.

Neto, J., Dahiya, A. S., Zumeit, A., Christou, A., Ma, S., & Dahiya, R. (2023). Printed n-and p-channel transistors using silicon nanoribbons enduring electrical, thermal, and mechanical stress. ACS Applied Materials & Interfaces, 15(7), 9618-9628.

Dahiya, A. S., Christou, A., Neto, J., Zumeit, A., Shakthivel, D., & Dahiya, R. (2022). In Tandem Contact‐Transfer Printing for High‐Performance Transient Electronics. Advanced Electronic Materials, 8(9), 2200170.

Neto, J., Dahiya, A. S., Kumaresan, Y., Shakthivel, D., & Dahiya, R. (2021, June). V 2 O 5 nanowires-based flexible temperature sensor. In 2021 IEEE International Conference on Flexible and Printable Sensors and Systems (FLEPS) (pp. 1-4). IEEE.

Neto, J., Dahiya, A. S., & Dahiya, R. (2023). Influence of Printed Encapsulation Layer on the Mechanical Reliability and Performance of V₂O₅ Nanowires-Based Flexible Temperature Sensors. IEEE Journal on Flexible Electronics, 2(2), 168-174.

Neto, J., Dahiya, A. S., Christou, A., Zumeit, A., De Pamphilis, L., & Dahiya, R. (2023, July). Dual-Gate Transistors Using Contact Printed ZnO Nanowires. In 2023 IEEE International Conference on Flexible and Printable Sensors and Systems (FLEPS) (pp. 1-4). IEEE.

Neto, J., Dahiya, A. S., & Dahiya, R. (2022, July). Influence of Encapsulation on the Performance of V 2 O 5 Nanowires-Based Temperature Sensors. In 2022 IEEE International Conference on Flexible and Printable Sensors and Systems (FLEPS) (pp. 1-4). IEEE.