Developing the Surface Chemistry of Transparent Butyl Rubber for Impermeable Stretchable Electronics

Transparent butyl rubber is a new elastomer that has the potential to revolutionize stretchable electronics due to its intrinsically low gas permeability. Encapsulating organic electronic materials and devices with transparent butyl rubber protects them from problematic degradation due to oxygen and moisture, preventing premature device failure and enabling the fabrication of stretchable organic electronic devices with practical lifetimes. Here, we report a methodology to alter the surface chemistry of transparent butyl rubber to advance this material from acting as a simple device encapsulant to functioning as a substrate primed for direct device fabrication on its surface. We demonstrate a combination of plasma and chemical treatment to deposit a hydrophilic silicate layer on the transparent butyl rubber surface to create a new layered composite that combines Si-OH surface chemistry with the favorable gas-barrier properties of bulk transparent butyl rubber. We demonstrate that these surface Si-OH groups react with organosilanes to form self-assembled monolayers necessary for the deposition of electronic materials, and furthermore demonstrate the fabrication of stretchable gold wires using nanotransfer printing of gold films onto transparent butyl rubber modified with a thiol-terminated self-assembled monolayer. The surface modification of transparent butyl rubber establishes this material as an important new elastomer for stretchable electronics and opens the way to robust, stretchable devices

Metal-Interface-Elastomer (MINE) Structures for Stretchable Electronics

The future of soft, conformable, and robust wearable electronics will require elastomers to provide mechanical stabilization, a soft surface to interact with human wearers, and a crucial physical barrier to protect stretchable devices from the environment. It is a difficult challenge, however, for a single elastomer to fulfill each of these needs. Here, we present a new approach that fuses a membrane of poly(dimethylsiloxane) (PDMS) onto the surface of a transparent butyl rubber (T-IIR) substrate using an organosilane-based molecular glue. The resulting membrane-interface-elastomer (MINE) structures uniquely combine the surface chemistry of PDMS with the intrinsically low gas permeability of T-IIR for the fabrication of robust stretchable devices. Our most intriguing finding, however, is that the T-IIR-PDMS interface, buried microns below the PDMS surface, exerts a remarkable influence on metal films deposited on the PDMS membrane surface from below, improving stretching and conductance performance by orders of magnitude

Transparent, Stretchable, and Conductive SWNT Films Using Supramolecular Functionalization and Layer-by-Layer Self-Assembly

We demonstrate films of single-walled carbon nanotubes (SWNTs) on the elastomer polydimethylsiloxane (PDMS) that are stretchable, conductive, and transparent. Our fabrication method uses the supramolecular functionalization of SWNTs with conjugated polyelectrolytes to generate aqueous dispersions of positively- and negatively-charged SWNTs, followed by layer-by-layer self-assembly onto a PDMS substrate. Adding bilayers of positively- and negatively-charged SWNTs to the surface causes the sheet resistance and the % transmittance of the film to both progressively decrease. The sheet resistance decreases sharply in the first five bilayers as the layer-by-layer process efficiently establishes the percolation network, whereas the % transmittance declines more gradually. Films with 25 bilayers are transparent (75% at 550 nm) and conductive (560 ± 90 ohms/sq). The combination of electrostatic and pi-stacking forces very effectively bind the SWNTs within the film, producing smooth film surfaces (root-mean-square roughness of 18 nm) and enabling the films to remain conductive up to 80% elongation. We demonstrate the use of the SWNT films as transparent conductive electrodes in light-emitting devices and as soft strain sensors that are both wearable and transparent

New Elastomeric Materials and Functional Composites for Stretchable Electronics

This dissertation reports a diverse range of new components for the fabrication of soft flexible, stretchable and wearable electronic devices. The components investigated spans design and development of a new elastomer, layered elastomeric material, investigation and modification of surface chemistries, and development of new techniques for fabrication of stretchable, conductive composites using nanomaterials and metals. Simple, low-cost, benchtop techniques for the fabrication of the functional materials has been a strong focus of the work reported in this dissertation. Chapter 2 reports the development of a new transparent formulation of a renowned elastomer, butyl rubber, that enables its use in stretchable electronics applications. We design a new compression molding method to prepare highly smooth and transparent butyl rubber (T-IIR) substrates. We demonstrate the T-IIR protection to sensitive electronic materials from degradation and corrosion by oxygen and moisture to extend the lifetimes of stretchable devices. The demonstrated benefits positions T-IIR as an important elastomer for future generation of impermeable stretchable electronics. Chapter 3 examines the surface properties of T-IIR reported in Chapter 2 and reports methods to modify the surface chemistry of T-IIR to enable the deposition of electronic materials. This report advances the new elastomer from being a mere encapsulant to a substrate for direct device fabrication on its surface. As a proof of concept, we demonstrate the deposition of stretchable gold films on the organosilane-modified surface of T-IIR. Chapter 4 expands upon the work presented in Chapter 3 and reports the fabrication of a multilayered elastomeric composite built upon T-IIR. The properties of the composite enables the deposition of stretchable metal films, while T-IIR prevents degradation from gases and water vapor when the composite/metal is used in electronic devices. We demonstrate the fabrication and long lifetime performance of wires, circuits and light-emitting devices using metal films on the T-IIR-based elastomeric composite as electrodes. Chapter 5 investigates a low-cost, scalable technique for fabrication of transparent, stretchable and conductive films on elastomer using electrostatic self-assembly of functionalized nanomaterials. Layer-by-layer assembly of functionalized single-walled carbon nanotubes (SWNTs) provide precise control over transparency and conductivity. We demonstrate these films on elastomer, in strain sensor and light-emitting device fabrication. Chapter 6 demonstrates another class of conductive material, liquid metal alloys, for fabrication of soft elastomeric composites for large-area electronic devices. The method focuses on the confinement of liquid metal alloy within elastomeric matrix while taking advantage of the free-standing liquid metal properties. The work examines the use of soft conductors as interconnects to measure conductivity of thin films and investigates their use as electrodes in light-emitting devices

Post COVID sequelae among COVID-19 survivors: insights from the Indian National Clinical Registry for COVID-19

Introduction The effects of COVID-19 infection persist beyond the active phase. Comprehensive description and analysis of the post COVID sequelae in various population groups are critical to minimise the long-term morbidity and mortality associated with COVID-19. This analysis was conducted with an objective to estimate the frequency of post COVID sequelae and subsequently, design a framework for holistic management of post COVID morbidities.Methods Follow-up data collected as part of a registry-based observational study in 31 hospitals across India since September 2020–October 2022 were used for analysis. All consenting hospitalised patients with COVID-19 are telephonically followed up for up to 1 year post-discharge, using a prestructured form focused on symptom reporting.Results Dyspnoea, fatigue and mental health issues were reported among 18.6%, 10.5% and 9.3% of the 8042 participants at first follow-up of 30–60 days post-discharge, respectively, which reduced to 11.9%, 6.6% and 9%, respectively, at 1-year follow-up in 2192 participants. Patients who died within 90 days post-discharge were significantly older (adjusted OR (aOR): 1.02, 95% CI: 1.01, 1.03), with at least one comorbidity (aOR: 1.76, 95% CI: 1.31, 2.35), and a higher proportion had required intensive care unit admission during the initial hospitalisation due to COVID-19 (aOR: 1.49, 95% CI: 1.08, 2.06) and were discharged at WHO ordinal scale 6–7 (aOR: 49.13 95% CI: 25.43, 94.92). Anti-SARS-CoV-2 vaccination (at least one dose) was protective against such post-discharge mortality (aOR: 0.19, 95% CI: 0.01, 0.03).Conclusion Hospitalised patients with COVID-19 experience a variety of long-term sequelae after discharge from hospitals which persists although in reduced proportions until 12 months post-discharge. Developing a holistic management framework with engagement of care outreach workers as well as teleconsultation is a way forward in effective management of post COVID morbidities as well as reducing mortality