Tragacanth gum as green binder for sustainable water-processable electrochemical capacitor

9Enabling green fabrication processes for energy storage devices is becoming a key aspect in order to achieve a sustainable fabrication cycle. Here we focus on the exploitation of the tragacanth gum, an exudated gum like arabic and karaya gums, as green binder for the preparation of carbon-based for electrochemical capacitors. The electrochemical performance of tragacanth (TRGC)-based electrodes are thoroughly investigated and compared with another water-soluble binder largely used in this field, i.e. sodium-carboxymethyl cellulose (CMC). Apart from the higher sustainability both in production and processing, TRGC exhibits a lower impact on the obstruction of pores in the final active material film with respect to CMC, allowing for more available surface area. This directly impacts on the electrochemical performances resulting in a higher specific capacitance and better rate capability. Moreover, the TRGC-based supercapacitor shows a superior thermal stability than CMC with a capacity retention of about 80 % after 10.000 cycles at 70 °C.partially_openopenScalia, Alberto; Zaccagnini, Pietro; Armandi, Marco; Latini, Giulio; Versaci, Daniele; Lanzio, Vittorino; Varzi, Alberto; Passerini, Stefano; Lamberti, AndreaScalia, Alberto; Zaccagnini, Pietro; Armandi, Marco; Latini, Giulio; Versaci, Daniele; Lanzio, Vittorino; Varzi, Alberto; Passerini, Stefano; Lamberti, Andre

Tragacanth Gum as Green Binder for Sustainable Water-Processable Electrochemical Capacitor

Enabling green fabrication processes for energy storage devices is becoming a key aspect in order to achieve a sustainable fabrication cycle. Here, the focus was on the exploitation of the tragacanth gum, an exudated gum like arabic and karaya gums, as green binder for the preparation of carbon‐based materials for electrochemical capacitors. The electrochemical performance of tragacanth (TRGC)‐based electrodes was thoroughly investigated and compared with another water‐soluble binder largely used in this field, sodium‐carboxymethyl cellulose (CMC). Apart from the higher sustainability both in production and processing, TRGC exhibited a lower impact on the obstruction of pores in the final active material film with respect to CMC, allowing for more available surface area. This directly impacted the electrochemical performance, resulting in a higher specific capacitance and better rate capability. Moreover, the TRGC‐based supercapacitor showed a superior thermal stability compared with CMC, with a capacity retention of about 80 % after 10000 cycles at 70 °C

Small footprint optoelectrodes using ring resonators for passive light localization

The combination of electrophysiology and optogenetics enables the exploration of how the brain operates down to a single neuron and its network activity. Neural probes are in vivo invasive devices that integrate sensors and stimulation sites to record and manipulate neuronal activity with high spatiotemporal resolution. State-of-the-art probes are limited by tradeoffs involving their lateral dimension, number of sensors, and ability to access independent stimulation sites. Here, we realize a highly scalable probe that features three-dimensional integration of small-footprint arrays of sensors and nanophotonic circuits to scale the density of sensors per cross-section by one order of magnitude with respect to state-of-the-art devices. For the first time, we overcome the spatial limit of the nanophotonic circuit by coupling only one waveguide to numerous optical ring resonators as passive nanophotonic switches. With this strategy, we achieve accurate on-demand light localization while avoiding spatially demanding bundles of waveguides and demonstrate the feasibility with a proof-of-concept device and its scalability towards high-resolution and low-damage neural optoelectrodes

Neural optoelectrodes merging semiconductor scalability with polymeric-like bendability for low damage acute in vivo neuron readout and stimulation

Neural optoelectrodes can read and manipulate large numbers of neurons in vivo. However, state-of-the-art devices rely on either standard microfabrication materials (i.e., silicon and silicon nitride), which result in high scalability and throughput but cause severe brain damage due to implant stiffness, or polymeric devices, which are more compliant but whose scalability and implantation in the brain are challenging. Here, we merge the gap between silicon-based fabrication scalability and low (polymeric-like) stiffness by fabricating a nitride and oxide-based optoelectrode with a high density of sensing microelectrodes, passive photonic circuits, and a very small tip thickness (5 μm). We achieve this by removing all the silicon supporting material underneath the probe's tip - while leaving only the nitride and glass optical ultrathin layers - through a single isotropic etch step. Our optoelectrode integrates 64 electrodes and multiple passive optical outputs, resulting in a cross-sectional area coefficient (the cross section divided by the number of sensors and light emitters) of 3.1 - smaller than other optoelectrodes. It also combines a low bending stiffness (∼4.4 × 10-11 N m2), comparable or approaching several state-of-the-art polymeric optoelectrodes. We tested several mechanical insertions of our devices in vivo in rats and demonstrated that we can pierce the pia without using additional temporary supports

High-density electrical and optical probes for neural readout and light focusing in deep brain tissue

To advance neuroscience in vivo experiments, it is necessary to probe a high density of neurons in neural networks with single-cell resolution and be able to simultaneously use different techniques, such as electrophysiological recordings and optogenetic intervention, while minimizing brain tissue damage. We first fabricate electrical neural probes with a high density of electrodes and small tip profile (cross section of shank: 47-μm width × 16-μm thickness). Then, with similar substrate and fabrication techniques, we separately fabricate optical neural probes. We finally indicate a fabrication method that may allow integrating the two functionalities into the same device. High-density electrical probes have been fabricated with 64 pads. Interconnections to deliver the signal are 120-nm wide, and the pads are 5 × 25 μm. Separate optical probes with similar shank dimensions with silicon dioxide and silicon nitride ridge single-mode waveguides have also been fabricated. The waveguide core cross section is 250 nm × 160 nm. Light is focused above the waveguide plane in 2.35-μm diameter spots. The actual probes present two output focusing gratings on the shank

Label-free DNA biosensing by topological light confinement

Large-area and transparent all-dielectric metasurfaces sustaining photonic bound states in the continuum (BICs) provide a set of fundamental advantages for ultrasensitive biosensing. BICs bridge the gap of large effective mode volume with large experimental quality factor. Relying on the transduction mechanism of reactive sensing principle, herein, we first numerically study the potential of subwavelength confinement driven by topological decoupling from free space radiation for BIC-based biosensing. Then, we experimentally combine this capability with minimal and low-cost optical setup, applying the devised quasi-BIC resonator for PNA/DNA selective biosensing with real-time monitoring of the binding event. A sensitivity of 20 molecules per micron squared is achieved, i.e. 0.01 pg. Further enhancement can easily be envisaged, pointing out the possibility of single-molecule regime. This work aims at a precise and ultrasensitive approach for developing low-cost point-of-care tools suitable for routine disease prescreening analyses in laboratory, also adaptable to industrial production control

Label-free DNA biosensing by topological light confinement

Large-area and transparent all-dielectric metasurfaces sustaining photonic bound states in the continuum (BICs) provide a set of fundamental advantages for ultrasensitive biosensing. BICs bridge the gap of large effective mode volume with large experimental quality factor. Relying on the transduction mechanism of reactive sensing principle, herein, we first numerically study the potential of subwavelength confinement driven by topological decoupling from free space radiation for BIC-based biosensing. Then, we experimentally combine this capability with minimal and low-cost optical setup, applying the devised quasi-BIC resonator for PNA/DNA selective biosensing with real-time monitoring of the binding event. A sensitivity of 20 molecules per micron squared is achieved, i.e. 0.01 pg. Further enhancement can easily be envisaged, pointing out the possibility of single-molecule regime. This work aims at a precise and ultrasensitive approach for developing low-cost point-of-care tools suitable for routine disease prescreening analyses in laboratory, also adaptable to industrial production control