Periodic Reporting for period 2 - LEAPh (Light-modulated organic Electrolyte-gAted Phototransistors)
Período documentado: 2022-07-01 hasta 2023-06-30
In recent years, organic bioelectronics has emerged as a potentially disruptive technology, introducing innovative devices with unprecedented features of biocompatibility and functionality. The potential of organic materials resides not only in their favorable mechanical properties, which comply to those of biological tissues, but also on their ability to enable mixed electronic and ionic transport and on the possibility to finely tune their optoelectronic properties, such as optical absorption, charge photogeneration and transport. Similarly, the development of organic optoelectronic devices, largely employed in light-emitting and photovoltaic technologies (e.g. OLEDs and OPVs), has led in recent years to the creation of a number of bioelectronic light and image sensors able to restore or mimic human vision.
In addition, the synthesis of organic compounds can be tuned to further improve biocompatibility and to allow for chemical or biochemical functionalization (bioconjugation), as well as to enable cost-effective and scalable processability of materials. For these reasons, a plethora of biocompatible, mechanically compliant, large area, multipoint biosensing and stimulating devices are now available. Existing technologies range from either chronic or transient implantable biosensors and drug-delivery systems, to electronic transducers for in vitro and in vivo neuronal activity, artificial retinas, ion pumps and ingestible devices. Moreover, organic neuromorphic devices are expected to contribute to the development of neural networks, while research on disposable lab-on-a-chip systems and epidermal electronics is generating novel interaction routes between biological systems, bioelectronics devices, and consumer electronics, such as smartphones and portable devices.
Because of the general involvement of ionic transport in biological environments, organic bioelectronic devices are inherently slow, i.e. characterized by slow switching capabilities, limited to few kHz. This fundamental aspect brings along some limitations and non-idealities, such as low-frequency operation and fluctuations of the operating parameters of the devices. The ultimate goal of the LEAPh project is to develop a Light-modulated organic Electrolyte-gAted Phototransistor. This novel kind of bioelectronic device is specifically devised to address in an unprecedented way the low-operating frequency of current bioelectronics, possibly reaching the MHz regime, as well as providing a noise-free measurement of biochemical and biological interactions. Moreover, the same technology could pave the way towards a new class of low-voltage organic electro-optical systems.
In addition, the synthesis of organic compounds can be tuned to further improve biocompatibility and to allow for chemical or biochemical functionalization (bioconjugation), as well as to enable cost-effective and scalable processability of materials. For these reasons, a plethora of biocompatible, mechanically compliant, large area, multipoint biosensing and stimulating devices are now available. Existing technologies range from either chronic or transient implantable biosensors and drug-delivery systems, to electronic transducers for in vitro and in vivo neuronal activity, artificial retinas, ion pumps and ingestible devices. Moreover, organic neuromorphic devices are expected to contribute to the development of neural networks, while research on disposable lab-on-a-chip systems and epidermal electronics is generating novel interaction routes between biological systems, bioelectronics devices, and consumer electronics, such as smartphones and portable devices.
Because of the general involvement of ionic transport in biological environments, organic bioelectronic devices are inherently slow, i.e. characterized by slow switching capabilities, limited to few kHz. This fundamental aspect brings along some limitations and non-idealities, such as low-frequency operation and fluctuations of the operating parameters of the devices. The ultimate goal of the LEAPh project is to develop a Light-modulated organic Electrolyte-gAted Phototransistor. This novel kind of bioelectronic device is specifically devised to address in an unprecedented way the low-operating frequency of current bioelectronics, possibly reaching the MHz regime, as well as providing a noise-free measurement of biochemical and biological interactions. Moreover, the same technology could pave the way towards a new class of low-voltage organic electro-optical systems.
In the first phase of the LEAPh project, undertaken in collaboration with the group of Prof. Alberto Salleo (Stanford University), we developed a novel device configuration consisting of an organic electrolyte-gated transistor embedded within a microwave resonating structure. The combination of these two coplanar components onto a single flexible substrate forms a microwave antenna whose interaction with electromagnetic waves is actively controlled by the organic transistor – for example by modulating its microwave reflectivity – hence providing a pathway towards wireless signal communication.
During the initial stages of the project, we demonstrated the operation of these novel microwave devices with an emerging class of high-performance organic mixed ion-electron conductors. Thanks to a collaboration with the group of Prof. Iain McCullough (University of Oxford), we were able to demonstrate devices operating in both depletion and accumulation modes, with both p-type and n-type operation.
The unique operating characteristics of our tunable resonators can be selectively leveraged to target specific functionalities that benefit from the wireless detection of low-voltage signals, for example in bioelectronic and healthcare application scenarios. We hence exploited our devices to transduce bioelectrochemical signals while simultaneously encoding the resulting information within the backscattered radiation from the resonators. This combined transduction/ modulation scheme is of particular technological appeal when implemented in the 2-4 GHz range, which is largely exploited for a plethora of communication protocols (e.g. Bluetooth, WiFi, medical devices, remote switches, etc.). We demonstrated the wireless and battery-less transduction of metabolites in aqueous analytes by coupling our tunable microwave resonators with a two-electrode enzymatic reaction cell for glucose sensing.
The results of our work have been presented at three international conferences (Fall MRS 2021, Spring MRS 2022, IEEE IFETC 2023), and they were the object of a research article (Tan, S. T. M., et al., Conjugated Polymers for Microwave Applications: Untethered Sensing Platforms and Multifunctional Devices. Adv. Mater. 2022, 2202994), with another two articles in preparation.
During the initial stages of the project, we demonstrated the operation of these novel microwave devices with an emerging class of high-performance organic mixed ion-electron conductors. Thanks to a collaboration with the group of Prof. Iain McCullough (University of Oxford), we were able to demonstrate devices operating in both depletion and accumulation modes, with both p-type and n-type operation.
The unique operating characteristics of our tunable resonators can be selectively leveraged to target specific functionalities that benefit from the wireless detection of low-voltage signals, for example in bioelectronic and healthcare application scenarios. We hence exploited our devices to transduce bioelectrochemical signals while simultaneously encoding the resulting information within the backscattered radiation from the resonators. This combined transduction/ modulation scheme is of particular technological appeal when implemented in the 2-4 GHz range, which is largely exploited for a plethora of communication protocols (e.g. Bluetooth, WiFi, medical devices, remote switches, etc.). We demonstrated the wireless and battery-less transduction of metabolites in aqueous analytes by coupling our tunable microwave resonators with a two-electrode enzymatic reaction cell for glucose sensing.
The results of our work have been presented at three international conferences (Fall MRS 2021, Spring MRS 2022, IEEE IFETC 2023), and they were the object of a research article (Tan, S. T. M., et al., Conjugated Polymers for Microwave Applications: Untethered Sensing Platforms and Multifunctional Devices. Adv. Mater. 2022, 2202994), with another two articles in preparation.
The results obtained so far pioneer the use of a novel class of conjugated polymer semiconductors as tuning elements within microwave resonator. Besides the remarkable potential for these devices to operate as wireless bioelectronic sensors, these elements also constitute the building blocks of emerging microwave optics technologies known as metadevices. The unique redox-tunability and charge modulation capability of organic electronic materials, traditionally considered unsuitable for radio-frequency and microwave applications, pave the way for a generation of microwave devices with bespoke operating modes and conditions, while maintaining performances comparable to other state-of-the-art metadevice tuning strategies.
Nonetheless, much is yet to be understood about the properties of organic (semi)conductors operating in microwave structures, at both the materials and the device level. For example, the spectral limitations of this tuning strategy are fundamentally unknown, as the traditional structure-function relationships of this class of semiconductors are not well studied at the radio-frequencies of interest here. Future investigations will address these fundamental questions, while also exploring new metadevice configurations and applications based on this tuning strategy. The proof-of-concept devices developed during LEAPh indeed suggest that organic reconfigurability based on organic electronic materials could potentially lead to new and unexplored photonic platforms across the microwave spectrum, and possibly all the way to the THz.
Examples of such applications include untethered and self-powered neural interfaces able to transduce signals from electrogenic cells and tissues, implantable/wearable, and self-powered microwave systems for healthcare applications, and multifunctional reconfigurable metasurfaces fabricated on large areas with cost-effective techniques and environmentally sustainable materials.
Nonetheless, much is yet to be understood about the properties of organic (semi)conductors operating in microwave structures, at both the materials and the device level. For example, the spectral limitations of this tuning strategy are fundamentally unknown, as the traditional structure-function relationships of this class of semiconductors are not well studied at the radio-frequencies of interest here. Future investigations will address these fundamental questions, while also exploring new metadevice configurations and applications based on this tuning strategy. The proof-of-concept devices developed during LEAPh indeed suggest that organic reconfigurability based on organic electronic materials could potentially lead to new and unexplored photonic platforms across the microwave spectrum, and possibly all the way to the THz.
Examples of such applications include untethered and self-powered neural interfaces able to transduce signals from electrogenic cells and tissues, implantable/wearable, and self-powered microwave systems for healthcare applications, and multifunctional reconfigurable metasurfaces fabricated on large areas with cost-effective techniques and environmentally sustainable materials.