β-Cyclodextrin-Based Ultrahigh Stretchable, Flexible, Electro- and Pressure-Responsive, Adhesive, Transparent Hydrogel as Motion Sensor

Abstract

In the present work, a multiple-stimuli-responsive hydrogel has been synthesized via polymerization of acrylamide (AAm) and N-hydroxy methyl acrylamide (HMAm) on β-cyclodextrin (β-CD). The synthesized hydrogel β-CD-g-(pAAm/pHMAm) exhibited various striking features like ultrahigh stretchability (>6000%), flexibility, stab resistivity, self-recoverability, electroresponsiveness, pressure-responsiveness, adhesiveness, and high transparency (>90%). Besides, the hydrogel has demonstrated enhanced biocompatibility, UV resistance, and thermoresponsive shape memory behaviors. On the basis of these attractive characteristics of the hydrogel, a flexible pressure sensor for the real-time monitoring of human motion with superior biocompatibility and transparency was fabricated. Moreover, due to the nanofibrillar surface morphology of the β-CD-g-(pAAm/pHMAm) hydrogel, the sensor based on the gel exhibited high sensitivity (0.053 kPa–1 for 0–3.3 kPa). The flexible sensor demonstrates very fast response time (130 ms-210 ms) with adequate stability (5000 cycles). Interestingly, the sensor can rapidly sense both robust (index finger and wrist) motions as well as tiny (swallowing and phonation) physiological actions. In addition, this adhesive hydrogel patch also acts as a potential carrier for the sustained topical release of (∼80.8% in 48 h) the antibiotic drug gentamicin sulfate.

Recent advances in various stimuli-responsive hydrogels: from synthetic designs to emerging healthcare applications

“…Mechano-responsive hydrogels generally change their mechanics and conformation under a wide range of loads. 334 Through self-assembly alterations or by replicating the structure of strain-stiffening biopolymers, the mechanical response of the hydrogels can be typically induced. Various artificial gels, like polyisocyanopeptide (PIC) based gels, with strain-stiffing and biomimetic characteristics have been reported.…”

Aggressive strategies for regenerating intervertebral discs: stimulus-responsive composite hydrogels from single to multiscale delivery systems

“…β-CD-based hydrogels have good self-healing ability and pressure responsiveness. Roy et al 206 grafted acrylamide (AAm) and N -hydroxymethylacrylamide (HMAm) onto the β-CD ring to develop pH, thermal, and pressure multi-responsive composite hydrogels and excellent shape memory behavior. In addition, the nanofiber surface morphology of this system confers high sensitivity and sufficient stability to the gel-based sensor, allowing local sustained release of gentamicin sulfate.…”

Silver Nanowire/Silver/Poly(dimethylsiloxane) as Strain Sensors for Motion Monitoring

“…With the development of material technology, flexible devices attract more and more attention in daily application equipment, , such as stretchable light-emitting diodes, flexible smartphones and smartwatches, energy harvesting devices, , e-skins, and wearable sensors. − Particularly, to encourage promising applications in human interaction, physiology activity monitoring, and on-point healthcare, , flexible and wearable sensors have been rapidly developed in recent years. Flexible sensors reported to date can be classified into resistive, − piezoelectric, − capacitive, − and triboelectric types depending on their sensing mechanism to test tensile force, pressure, etc.…”