Tuning the Performance of Conjugated Polymers by Post-polymerisation Modification.
Controlling the band gap, molecular packing and absolute energy levels of conjugated polymers and oligomers is fundamentally important for their utilisation in a number of applications. Most approaches utilize the co-polymerisation of various co-monomer materials for this goal. However establishing structure-property relationships by varying co-monomer ratio can be challenging, as it is difficult to disentangle the influence of changes in the backbone chemistry from variations in the molecular weight, end-groups and polydispersity. Here I will discuss alternate approaches based on the functionalisation of pre-formed conjugated polymers, enabling the synthesis of libraries with consistent dispersity and length. I will highlight how such approaches can be utilised to carefully tune hydrophilicity, control electron affinity, balance ion penetration versus swelling behaviour or introduce stimuli responsive behaviour.
Sequence and assembly of conjugated polymer by high-resolution imaging
In this talk I will demonstrate that high resolution scanning tunnelling microscopy (STM) is capable of delivering crucial information — that cannot be achieved by any other current analytical method — about “real world” electronic and energy materials. In particular, I will show that by combining vacuum electrospray deposition (ESD) and high-resolution STM, it is possible to image conjugated polymers used in organic electronics and photovoltaic devices with unprecedented details. Based on this, it becomes possible to sequence the polymers by visual inspection and to determine their molecular mass distribution by simply counting the repeat units. Moreover, I will demonstrate that we can precisely determine the nature, locate the position, and ascertain the number of synthetic defects in the polymer backbone.1-2 The analysis of our high- resolution images univocally demonstrates that one of the main drivers for backbone conformation and polymer self-assembly is the maximization of alkyl side-chain interdigitation. On this basis, we investigate the 2D assembly of a series of conjugated polymers with the aim of gaining insight in the molecular microstructure of the corresponding 3D functional thin films.4,5
KAUST Campus Library
On the role of the (de)localization length
Charge transport in structurally disordered or partially ordered organic semiconductors is typically understood in terms of thermally activated tunneling between localized states, or in short: hopping. The associated length scale, the localization length, is typically assumed to be between 0.1 and 1 nm. In the context of organic photovoltaics, the concept of charge delocalization appears on a regular basis to rationalize the high yield of charge generation. Here, the idea is that higher-lying states can have a much reduced localization length, or even be band-like in nature. In this talk, I will discuss our recent work on the role of the localization length in organic thermoelectrics. Specifically, I will show that the localization length is fundamentally energy dependent, with higher-energy states being more spread out. This allows to quantitatively explain an unexpected power-law dependence of the DC conductivity of doped organic semiconductors on charge carrier concentration. Moreover, I will argue that the counter-intuitive simultaneous increase in Seebeck coefficient and conductivity in uniaxially aligned polymer films can be explained in terms of an anisotropy in the localization length, but only for films that are not fully amorphous. Finally, I will discuss how the localization length can actually be measured and show first results of such measurements.
An Overview of Second Sound in Solid Materials
The study of heat transport beyond Fourier’s regime has attracted renewed interest in recent years. Great efforts have been performed to unravel the physical properties of thermal waves, as well as the experimental conditions that are necessary for their observation. Applications based on such concepts have been envisioned and discussed extensively already in many recent publications[1–3].The spatio-temporal propagation of the temperature field in the form of waves is known as “second sound,” a term that was adopted in analogy to “first sound” (or simply “sound”, i.e. mechanical lattice vibrations). First and Second Sound are both described by a similar equation where the variables have a different physical meaning, i.e. pressure and temperature, respectively.Second sound is known as the thermal transport regime where heat is carried by temperature waves. Its experimental observation was previously restricted to a small number of materials (solid He, Bi, NaF, SrTiO3, and graphite), usually in rather narrow temperature windows. We show that it is possible to overcome these limitations by driving the system with a rapidly varying temperature field. High-frequency second sound is demonstrated in bulk natural Ge between 7 kelvin and room temperature by studying the phase lag of the thermal response under a harmonic high frequency external thermal excitation, and addressing the relaxation time and the propagation velocity of the heat waves. In this talk, I will present a comprehensive overview on the historical observation of second sound, with special emphasis on the appearance of different flavors of thermal waves depending on the thermal excitation conditions. In particular, I will discuss the recent experimental observation of high frequency second sound
Building 5, Level 5, Room 5209
Outside Al Marsa Yacht Club
Soft and flexible bioelectronics for brain-machine interface
Large-scale brain mapping via brain-machine interface is important for deciphering neuron population dynamics, understanding and alleviating neurological disorders, and building advanced neuroprosthetics. Ultimately, brain mapping aims to simultaneously record activities from millions, if not billions, of neurons with single-cell resolution, millisecond temporal resolution and cell-type specificity over the time course of brain development, learning, and aging. In this talk, I will first introduce “tissue-like” soft bioelectronics that possess tissue-like properties, capable of tracking the electrical activities from the same neurons in the brain of behaving animals. Specifically, I will discuss the fundamental limits to the electrochemical impedance stability of soft electronic materials in bioelectronics and introduce our strategies to overcome these limits, enabling a scalable platform for the large-scale brain mapping. Then, I will discuss the building of “cyborg organisms”, where stretchable mesh-like electrode arrays are embedded in 2D sheets of stem/progenitor cells and reconfigured through 2D-to-3D organogenesis, enabling continuous 3D brain electrophysiology during brain development. Finally, I will discuss future perspectives that leverage the soft bioelectronics-brain interface to integrate single-cell spatial transcriptomics with electrical recording, opening opportunities for cell-type-specific brain mapping and functional brain cell atlas.
Tuning the molecular design of polymers to achieve self-assembled degradable, semiconducting, and stretchable composites
Next-generation electronics will autonomously respond to local stimuli and be seamlessly integrated with the human body, opening the doors for opportunities in environmental monitoring, advanced consumer products, and health diagnostics for personalized therapy. For example, biodegradable electronics promise to accelerate the integration of electronics with health care by obviating the need for costly device-recovery surgeries that increase infection risk. Moreover, the environmentally critical problem of discarded electronic waste would be relieved. The underpinning of such next-generation electronics is the development of new materials with a wide suite of functional properties beyond our current toolkit. Organic polymers are a natural bridge between electronics and soft matter, where the vast chemical design space allows tunability of electronic, mechanical, and transient properties. Our research group leverages the rich palette of polymer chemistry to design new materials encoded with information for self-assembly, degradability, and electronic transport. In this talk, I will share our progress on the molecular design of degradable semiconducting polymers featuring acid-labile motifs.
Electronics open the door to a wealth of promising biomedical therapies, from implanted devices that therapeutically stimulate organs, to regenerative medicines that use electrical cues to guide stem cell differentiation towards target lineages. Yet, a severe mismatch in mechanical properties like stiffness and stretchability at the bio-electronic interface remains a major challenge. In this talk, I will focus on materials approaches to address these mechanical mismatches, focusing on intrinsically flexible and stretchable conjugated polymer-based semiconductors and conductors. I discuss the multi-length scale design strategies that have enabled researchers to realize desirable mechanical properties without compromising on high electrical performance.
3D Printable Conducting Polymers for Bioelectronics
Ionic and electronic conducting polymers are searched in the area of bioelectronics for the development of innovative medical devices. The design of artificial scaffolds and devices which interact with the human body relies on the ability to control the mechanical and electrical signals, together with the material composition, topography and biocompatibility. New medical devices such as bioresponsive electrodes, biosensors, electronic skin and neural or muscle regeneration show the need of new conductive materials that can be printed. In this presentation we will show the recent activities carried out within the IONBIKE RISE project (www.ionbike-rise.eu) towards the development of printable conducting polymers. The presentation will include different materials and additive manufacturing methods based on the use of light or temperature such as:
-3D printing of supramolecular iongels by Fused Deposition Modelling
-3D printing of conducting PEDOT hydrogels by Stereolithography
-3D printing of biodegradable and conducting PEDOT/PLA polymers
Towards Sustainable Sensor Technologies through Hybrid Approaches
The growth of flexible and wearable electronics commensurate with the proliferation of microelectronic devices is enabling high impact applications in healthcare and robotics. However, as such electronic devices increase in number, an increasingly urgent need to create materials and devices that can be part of a circular or self-repairable economy becomes critical. In this talk, I will discuss using organic materials science and engineering approaches as a way to scale skin-like sensors for more sustainable technological and societal impact through self-healing or degradability.
To scale to human-like performance, neuromorphic engineering provides an exciting avenue to mimic the high performance of the human nervous systems and sensors. Critically, the energy efficiency of the human neural networks for learning relies on event-driven, temporally encoded action potential streams. In this talk, I will discuss how we can digitize tactile information through inspiration from somatosensory neural science.
We have developed an asynchronous protocol for parallel transmission of tactile information in an artificial peripheral nervous system we call ACES: Asynchronously Coded Electronic Skins. The parallel transmission encodes spatial temporal information with very high temporal precision (sub-100ns) even when large numbers > 10,000 sensor nodes are transmitting simultaneously. Such systems can be interfaced with soft sensors or flexible/stretchable electronics to enable more intuitive robotics and healthcare applications.
Semiconductor Initiative at KAUST
NanoManufacturing of Sustainable Circular Electronics
Sustainable manufacturing of goods is fast becoming an integral part of our societies. According to the United Nations, sustainable manufacturing can be defined as a form of manufacturing that meets "the needs of the present without compromising the ability of future generations to meet their own needs." However, achieving industrial sustainability presents significant techno-economic challenges, especially for the high-tech industries. One example is the modern electronic industry, which is responsible for the world's fastest-growing waste stream (E-waste). As technological progress accelerates, the need to transform these key industries has become more urgent. Unfortunately, adapting existing manufacturing methods to emerging electronics is challenging. Despite the difficulties, many new products have been gaining ground, broadening the marketplace while simultaneously transforming the manufacturing infrastructure. This talk will discuss our recent work towards up-scalable nanomanufacturing of emerging optoelectronic devices. I will show how developing new patterning techniques with eco-friendly materials, and processing paradigms can lead to greener and more circular electronics. Particular emphasis will be placed on innovative device concepts for different applications ranging from photovoltaics and large-area electronics to innovative forms of chemical reactors for green hydrogen generation and energy storage.
Organic mixed ionic-electronic conductors for low-power electronics
Organic mixed ionic-electronic conductors (OMIECs) are an enabling technology for many (opto-)electronic and energy harvesting/storage applications. In OMIECs, the strong coupling between ions and electrons enables efficient charge storage and signal transduction. When implemented as the active channel materials in organic electrochemical transistors (OECTs), OMIECs endow these devices with record-high transconductance, low operational voltage, and high current density. These attributes make the OECTs a promising technology for chemical and biological sensing, medical diagnostics, large-scale printed electronic circuitries, and neuromorphic computing. Here, we will summarize our effort to develop OMIECs for OECTs. We will discuss the impact of polymer backbone on the OECT performance and strategies to build low-power complementary circuits. We will show large-area printing/integration of these devices and demonstrate neuromimicking circuits capable of learning.
PhD Student, Chalmers University of Technology & CNRS - University of Strasbourg
Printed sensors for monitoring soil and plant conditions
High spatial density monitoring of the environment is essential for improving the understanding and management of natural systems. This is of particular importance in soils, where sensing can enable optimization of agricultural inputs, improved crop yields, increased carbon/nitrogen storage, and enhanced soil health. Print-based manufacturing of electronic systems enables the fabrication of large numbers of unconventional devices that utilize a wide range of materials that are compatible with natural environments, enabling the capture of useful, high-density information in these environments. This talk will describe recent progress in our lab on the study of printed electronic devices and systems for real-time monitoring of soil and plant conditions, with a focus on two specific sensor types. The first is a microbial activity sensor that utilizes biodegradable materials to monitor the decomposition activity of soil. The second is an ion-selective organic electrochemical transistor for evaluating nutrient concentrations that can be used in growth media and whole plant sap, as well as directly within plant tissue as an implant.
From UV to Near-Infrared light detection: next generation photodetectors for imaging and biometric applications
The current success of organic semiconductor technology is mainly driven by the development of organic light-emitting diodes (OLED), which are now routinely employed in display technologies. In the last decade, however, organic photovoltaics (OPV), leveraging the impressive improvement in device efficiency and stability, have gradually moved from a lab curiosity to a niche market. Their recent success has coincided with the rapid development of effective replacements for the fullerene-based materials that have been prevalent as electron acceptor materials until recently; namely the small molecule nonfullerene acceptors (NFAs). This relatively new class of materials offer a number of opportunities to develop new areas of research. Between those, organic photodetector (OPD), a technology based on organic photodiodes and thus closely related to OPV, is one of the most exciting. Recent efforts in the field of OPD have been focused on extending broadband detection into the near-infrared (NIR) region. The early absorption cut-off of solution processed organic semiconductors presents a challenge in achieving NIR detection, however, careful tuning of their chemical structures can help extend OPD responsivity into the infrared window. Here, we discuss how to design donor:acceptor blends and control charge carrier recombination in organic photodetectors for NIR light-to-current conversion for high efficiency and stable devices.
Organic neuromorphic electronics
Artificial intelligence applications have demonstrated their enormous potential for complex processing over the last decade. However, they are mainly based on digital operating principles while being part of an analogue world. Moreover, they still lack the efficiency and computing capacity of biological systems. Neuromorphic electronics emulate the analogue information processing of biological nervous systems. Neuromorphic electronics based on organic materials have the ability to emulate efficiently and with fidelity a wide range of bio-inspired functions. A prominent example of a neuromorphic device is based on organic mixed (ionic-electronic) conductors. Neuromorphic devices based on organic mixed conductors show volatile, non-volatile and tunable dynamics suitable for the emulation of synaptic plasticity and neuronal functions, and for the mapping of artificial neural networks in physical circuits. Finally, organic bio-inspired elements enable the local sensorimotor control/learning in robotics as well as neuromorphic concepts in sensing and biointerfacing.
Giulia received her Master’s degree in physics from the University of Milan, Italy, in 2011, with a thesis on the implantation of metal clusters in electroluminescent polymers for use in OLED devices. She then completed her PhD studies on the investigation of nanostructures on surfaces using scanning tunnelling microscopy in the group of Professor Harald Brune at the École Polytechnique Fédérale de Lausanne, Switzerland. Giulia joined Springer Nature in October 2015 for the launch of Nature Reviews Materials. She spent 2018 heading up the launch team of Nature Reviews Physics. Since January 2022, she is the Chief Editor of Nature Reviews Materials.
Giulia is primarily responsible for the areas of quantum materials, superconductivity, topological materials, 2D materials, metamaterials and structural materials.