Fabrication and Characterization of Roll-to-Roll-Coated Cantilever-Structured Touch Sensors

Abstract

It is common in the field of printed electronics that polydimethylsiloxane (PDMS) be used as a dielectric layer for capacitive sensors because of its high elasticity and restoration force. However, capacitive sensors with the PDMS dielectric layer have a lower sensitivity than those with an air-gap structure that has been fabricated by the conventional micro-electromechanical system (MEMS) process. This paper presents a productive method for fabricating air-gap structures for touch sensors by roll-to-roll slot-die coating. The air-gap is formed by coating and removing a sacrificial layer. Cantilever-structured capacitive touch sensors with an air-gap are fabricated as follows: First, the bottom electrode, the dielectric layer, and the poly(vinyl alcohol) (PVA) sacrificial layer are roll-to-roll slot-die-coated on a flexible substrate. In addition, the spacer layer is spin-coated. On the sacrificial and spacer layers, the top electrode and structural layer are formed by spin-coating. Then, the air-gap and cantilever structure are made by removing the sacrificial layer in water. The cantilever-structured sensor samples are examined in terms of sensitivity, hysteresis, and repeatability. In particular, the electrical performance of the samples is compared to those with the PDMS dielectric layer. Experimental results show that the cantilever-structured sensor samples have significantly higher sensitivity compared to those with the PDMS dielectric layer.

Flexible organic field-effect transistors-based biosensors: progress and perspectives

“…A productive roll-to-roll printed method for fabricating touch sensors (shown in Fig. 5 c) [ 41 , 147 ]. The bottom electrode, the dielectric, and the sacrificial layers were coated on a flexible substrate by roll-to-roll slot-die, while the roll-to-roll gravure printing was used to form the top electrode.…”

Biosensing, Characterization of Biosensors, and Improved Drug Delivery Approaches Using Atomic Force Microscopy: A Review

“…In CFM (Clear and Nealey 1999;Takano et al, 1999;Okabe et al, 2000;Fiorini et al, 2001;Kreller et al, 2002;Brewer and Leggett 2004;Gourianova et al, 2005;Cameron et al, 2006;Dague et al, 2007;Dufrene 2008;Foster et al, 2009;Sirghi et al, 2009;Barattin and Voyer 2011;Teobaldi et al, 2011;Alsteens et al, 2012;Picas et al, 2012;Beaussart et al, 2014;Hibino and Nakano-Nishida 2014), cantilever tips are chemically functionalized with particular functional groups for performing specific functions in a system. CFM relies on two approaches: microcantilever-based biosensors (MC-B) (Subramanian and Catchmark 2007;Lang and Gerber 2008;Gruber et al, 2011;Johnson and Mutharasan 2012;Peiner and Wasisto 2019;Bennett et al, 2020;Lee and Lee 2020;Mamou et al, 2021) and nanomechanical cantilever sensors (NCS) to achieve these goals of characterizing and understanding the system at single-molecule level with high reproducibility and repeatability. The microcantilever-based biosensing utilizes the specific binding of biomolecules for analytical sensing.…”

Recent Advances in High-Throughput Nanomaterial Manufacturing for Hybrid Flexible Bioelectronics

“…However, many other applications, such as implantable cerebrovascular and arterial stents, brain–machine interfaces, and fully printed wearable devices, are of tremendous interest [ 10 , 150 ]. Other systems have been successfully fabricated with high throughput methods, as summarized in Table 4 [ 37 , 129 , 162 , 163 , 164 , 165 , 166 ]. One area of critical interest is wearable electrophysiology monitoring.…”

“…Another interesting area of research is the development of capacitive touch sensors, which have been widely reported in the literature using traditional MEMS fabrication. Lee et al created such a touch sensor with an air gap instead of PDMS dielectric, and noted that the increased dielectric constant of air allowed for highly improved sensitivity (ΔC/C 0 (%) of 0.118%) and high linear sensing range from 0–20 KPa [ 37 ]. One area of high interest is in printing on TPU substrates, and this was the focus of a recent investigation by Jansson et al using screen-printed AgNP inks.…”

“…There are four crucial design challenges that must be met to make high throughput manufacturing of hybrid bioelectronics a reality, as depicted in Figure 1 [ 16 , 33 , 34 , 35 , 36 , 37 , 38 , 39 ], and all four are highly interdependent on each other. First, conductive nanomaterials must be identified and produced based on the final application requirements.…”