Wearable and Stretchable Soft Electronics Based on Ultrathin Gold Nanowires

Abstract

Wearable and highly flexible or stretchable electronics, including sensing devices, electrode components and energy storage devices are essential component for future human machine interfaces and bio monitoring. However, such electronics meet difficulties on current rigid and brittle wafer-based electric circuitry system. An alternative solution is to integrate the attributes of flexibility and stretchability of novel materials or novel structures to realize soft electronics. Nanotechnology offers new opportunities in designing soft electronics. Despite impressive recent advances, it remains challenging to achieve high conductivity, high stretchability and ultrathin device dimension into a single type of soft electronic device. Ultrathin gold nanowires (Au NWs) are mechanically flexible yet robust, which exhibited serpentine structure at nanoscale behaving like ‘polymer chains’ due to their ultrathin nature (2 nm in width, with an aspect ratio of >10,000). Hence, the Au NWs is intrinsically stretchable thus showing great potential in constructing novel soft electronics. To address the existing challenges, this thesis introduces a bunch of novel soft and wearable electronics based on ultrathin Au NWs. In details, we designed and fabricated highly sensitive pressure sensor, highly stretchable strain gauge sensor, flexible and transparent electrode, stretchable and transparent supercapacitor for the application of wearable biomedical monitoring, sports tracking, human machine interfacing and wearable energy supplier. In addition, ultrathin Au NWs possess several unique feature to soft electronics: 1) high sensitivity: a piezoresistive pressure sensor with sensitivity of 1.14/kPa can be achieved, which allowed real-time monitoring of human wrist pulse and tiny acoustic vibration. 2) High stretchability: a strain gauge sensor based on Au NWs thin film with thickness of only 1.64 μm could be working at strains exceeding 350%, >100 times larger than its metal counterparts. 3) High transparency and conductivity: we explored a simple yet efficient solution-based bottom-up strategy to fabricate Au NWs mesh film which could achieve both high transparency (>92%) and conductivity. 4) Ultrathin device dimensions: due to soft and serpentine-like geometry of ultrathin Au NWs, well-aligned Au NWs thin film (8 nm in thickness) could achieve high transparency (>90% at 550 nm) and excellent stretchability (>50%) simultaneously. Thus, the aim of this project is to develop a general and inexpensive strategy to construct wearable electronic devices based on ultrathin gold nanowires. We believed our strategies opened a new route to future wearable electronics.