Fabrication of High-Sensitivity Skin-Attachable Temperature Sensors with Bioinspired Microstructured Adhesive

Abstract

In this study, we demonstrate the fabrication of a highly sensitive flexible temperature sensor with a bioinspired octopus-mimicking adhesive. A resistor-type temperature sensor consisting of a composite of poly(N-isopropylacrylamide) (pNIPAM)-temperature sensitive hydrogel, poly(3,4-ethylenedioxythiophene) polystyrene sulfonate, and carbon nanotubes exhibits a very high thermal sensitivity of 2.6%·°C between 25 and 40 °C so that the change in skin temperature of 0.5 °C can be accurately detected. At the same time, the polydimethylsiloxane adhesive layer of octopus-mimicking rim structure coated with pNIPAM is fabricated through the formation of a single mold by utilizing undercut phenomenon in photolithography. The fabricated sensor shows stable and reproducible detection of skin temperature under repeated attachment/detachment cycles onto skin without any skin irritation for a long time. This work suggests a high potential application of our skin-attachable temperature sensor to wearable devices for medical and health-care monitoring.

Mimicking Human and Biological Skins for Multifunctional Skin Electronics

“…The muscle‐actuation‐induced pressure difference between the inside and outside of the suckers leads to switchable and conformal adhesion to arbitrary surfaces (Figure c) . Inspired by the adhesive mechanism of cephalopods, there have been recent achievements in biomimetic dry adhesives for medical/clinical patches, skin‐attachable temperature sensors, and transfer‐printing technique . Kim and co‐workers demonstrated a suction‐cup‐inspired dry adhesive system for a smart medical patch, enabling highly sensitive biometric sensing and transdermal drug delivery by combining with stretchable electronics and drug‐including nanoparticles (Figure d) .…”

Bioinspired Adhesive Architectures: From Skin Patch to Integrated Bioelectronics

“…Various devices incorporating biologically inspired architectures have recently been demonstrated to achieve high conformity to rough, often hairy and/or wet (e.g., perspiration, oil, and blood) surfaces of human interfaces for long‐term signaling. The architectures include gecko‐inspired nanohairs, insect pad‐like microfibrillars, frog pad‐inspired microchannels, and octopus sucker‐like microcavities . Pang et al reported a flexible pressure sensor with a microhairy interface to demonstrate signal amplification and measurements of the weak jugular venous pulses (JVPs) from a wireless transmitter .…”

“…While bioelectronics with microstructures have been used to increase detection of signal magnitudes by high conformity, diagnostic devices with bioinspired architectures for adhesion to skin have also drawn much attention. Patch‐type sensors with bioinspired dry adhesive architectures provide not only repetitive and long‐term attachment, but also stability for biosignal monitoring without conventional acrylic‐based glues or surgical suture . Kim et al proposed stretchable and conductive adhesives with mushroom‐shaped architectures to demonstrate cost‐effective and reusable all‐in‐one devices for biosignal measurements under active motions (i.e., moving, wrist‐curling, and writing) .…”

Simultaneously Optimize the Response Speed and Sensitivity of Low Dimension Conductive Polymers for Epidermal Temperature Sensing Applications

“…Next, we focus on improving its thermal sensitivity. As reported before, doping of PEDOT: PSS with other temperature-sensitive materials such as graphene (Trung et al, 2014(Trung et al, , 2016(Trung et al, , 2018 can further increase its response to temperature (Honda et al, 2014;Oh et al, 2018). Here, we applied the graphene doping strategy to further adjust the temperature sensitivity of PEDOT: PSS nanowires.…”

“…The thermosensitive mechanism of PEDOT: PSS can be explained by the structural change of PEDOT: PSS induced by the temperature change which eventually alters the conductivity of PEDOT: PSS (Takano et al, 2012;Zhou et al, 2014;Vuorinen et al, 2016). Previous studies on PEDOT: PSS based temperature sensors were focused on doping the PEDOT: PSS with other materials to enhance the device's response to temperature (Honda et al, 2014;Oh et al, 2018). However, understanding the control parameters regarding their response time to temperature change is less covered.…”