Freezing-Tolerant, Nondrying, Stretchable, and Adhesive Organohydrogels Inspired by the DNA Double Helix Structure for a Flexible Dual-Response Sensor

Abstract

Due to the unique flexibility and modifiability of hydrogels, hydrogel-based wearable sensors have drawn tremendous attention. However, traditional hydrogels rigidify or dehydrate at extreme temperatures because their included water freezes or evaporates, which greatly impedes the development and practical application of the hydrogel-based wearable sensor. Herein, a temperature-tolerant organohydrogel with self-healing properties, adhesiveness, plasticity, and high stretchability was designed by introducing the specific base pairs, adenine (A) and thymine (T), into the polyacrylamide network in a water–glycerol (Gly) binary solvent. The gelation process was mainly driven by the covalent cross-linking and the complementary base pairing of the double helix structure of DNA. The prepared organohydrogels exhibited a tensile strength of 35 kPa, a toughness of 667 kJ m–3, and were highly flexibile with a rupture elongation of 3870%. Moreover, the organohydrogel demonstrated an excellent adhesive performance toward diverse organic and inorganic substrates. The organohydrogel displayed a maximum peeling force and adhesion strength of organohydrogel to filter paper of 149 and 122 kPa, respectively. In addition, the organohydrogel presented a rapid self-healing efficiency, long-term moisture retention, and good conductivity, even at subzero temperatures (−20 °C), and can be assembled as a dual strain and thermal sensor to realize the dual-sensing. The organohydrogel strain sensor exhibited a higher sensing sensitivity [gauge factor (GF) = 11.99] over a broad strain range (∼660%) and long-term durability (>135 cycles) and can be attached to the human body to monitor human motion in real-time. Significantly, the organohydrogel still maintained its high strain sensitivity (GF = 9.76) even at a lower temperature. We envisage that this study will provide a theoretical guidance for the design and development of multifunctional conductive hydrogels with antifreezing and antidrying properties and extend the application of the hydrogel-based sensor in electronic skin, flexible control panel, wearable devices, and health monitoring in extreme environments.

Dual-Sensing, Stretchable, Fatigue-Resistant, Adhesive, and Conductive Hydrogels Used as Flexible Sensors for Human Motion Monitoring

“…Generally, the volume of polymer expanded and the viscosity of water decreased with increasing temperature, which facilitated the ion migration and increased the current of hydrogels. , As depicted in Figure l, the real-time current variation changed promptly and regularly when beakers filled with ice water (0 °C) and boiling water (100 °C) were alternately placed in contact with the hydrogel. When the hot source was placed close to hydrogels, the current increased, while when the cold source was placed close to the hydrogels the current decreased.…”

Multifunctional small biomolecules as key building blocks in the development of hydrogel-based strain sensors

“…21(c)). 255 The self-healing hydrogel showed excellent extensibility with a healing efficiency of 96.3% aer 60 min of contact between cut halves of the hydrogel. In addition, the hydrogel strongly adhered to various substrates, including nonpolar polymers, polar polymers, metals, skin, and ceramics, as indicated in Fig.…”

“…However, its building blocks, deoxyribose nucleotides, are small molecules with molecular weights less than 1 kDa. 253 DNA-inspired molecules such as deoxyribonucleotides (molecular weight < 1 kDa), including cytosine methacryloyl chloride, 254 acrylate adenine, thymine, 255,256 and adenosine monophosphate, 257 have been reported to improve the mechanical properties and adhesion of hydrogels to the skin. Zhang et al reported that the H-forming ability of adenosine monophosphate molecules can increase the stretchability of hydrogels (Fig.…”

“…Copyright 2021, Royal Society of Chemistry. Thymine and adenosine promote (c) self-healing and (d) adhesive properties in hydrogel strain sensors 255. Adapted with permission from ref 255.…”

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.…”