The authors reveal a thermal actuating bilayer that undergoes reversible deformation in response to low-energy thermal stimuli, for example, a few degrees of temperature increase. It is made of an aligned carbon nanotube (CNT) sheet covalently connected to a polymer layer in which dibenzocycloocta-1,5-diene (DBCOD) actuating units are oriented parallel to CNTs. Upon exposure to low-energy thermal stimulation, coordinated submolecular-level conformational changes of DBCODs result in macroscopic thermal contraction. This unique thermal contraction offers distinct advantages. It's inherently fast, repeatable, low-energy driven, and medium independent. The covalent interface and reversible nature of the conformational change bestow this bilayer with excellent repeatability, up to at least 70 000 cycles. Unlike conventional CNT bilayer systems, this system can achieve high precision actuation readily and can be scaled down to nanoscale. A new platform made of poly(vinylidene fluoride) (PVDF) in tandem with the bilayer can harvest low-grade thermal energy and convert it into electricity. The platform produces 86 times greater energy than PVDF alone upon exposure to 6 °C thermal fluctuations above room temperature. This platform provides a pathway to low-grade thermal energy harvesting. It also enables low-energy driven thermal artificial robotics, ultrasensitive thermal sensors, and remote controlled near infrared (NIR) driven actuators.
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Directional, Low-Energy Driven Thermal Actuating Bilayer Enabled by Coordinated Submolecular Switching
The authors reveal a thermal actuating bilayer that undergoes reversible
deformation in response to low-energy thermal stimuli, for example, a few
degrees of temperature increase. It is made of an aligned carbon nanotube
(CNT) sheet covalently connected to a polymer layer in which
dibenzocycloocta-1,5-diene (DBCOD) actuating units are oriented parallel to
CNTs. Upon exposure to low-energy thermal stimulation, coordinated
submolecular-level conformational changes of DBCODs result in macroscopic
thermal contraction. This unique thermal contraction offers distinct
advantages. It’s inherently fast, repeatable, low-energy driven, and medium
independent. The covalent interface and reversible nature of the
conformational change bestow this bilayer with excellent repeatability, up to
at least 70 000 cycles. Unlike conventional CNT bilayer systems, this system
can achieve high precision actuation readily and can be scaled down to
nanoscale. A new platform made of poly(vinylidene fluoride) (PVDF) in
tandem with the bilayer can harvest low-grade thermal energy and convert it
into electricity. The platform produces 86 times greater energy than PVDF
alone upon exposure to 6 °C thermal fluctuations above room temperature.
This platform provides a pathway to low-grade thermal energy harvesting. It
also enables low-energy driven thermal artificial robotics, ultrasensitive
thermal sensors, and remote controlled near infrared (NIR) driven actuators.
more »
« less
- NSF-PAR ID:
- 10344868
- Date Published:
- Journal Name:
- Advanced science
- ISSN:
- 2307-0536
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract The authors reveal a thermal actuating bilayer that undergoes reversible deformation in response to low‐energy thermal stimuli, for example, a few degrees of temperature increase. It is made of an aligned carbon nanotube (CNT) sheet covalently connected to a polymer layer in which dibenzocycloocta‐1,5‐diene (DBCOD) actuating units are oriented parallel to CNTs. Upon exposure to low‐energy thermal stimulation, coordinated submolecular‐level conformational changes of DBCODs result in macroscopic thermal contraction. This unique thermal contraction offers distinct advantages. It's inherently fast, repeatable, low‐energy driven, and medium independent. The covalent interface and reversible nature of the conformational change bestow this bilayer with excellent repeatability, up to at least 70 000 cycles. Unlike conventional CNT bilayer systems, this system can achieve high precision actuation readily and can be scaled down to nanoscale. A new platform made of poly(vinylidene fluoride) (PVDF) in tandem with the bilayer can harvest low‐grade thermal energy and convert it into electricity. The platform produces 86 times greater energy than PVDF alone upon exposure to 6 °C thermal fluctuations above room temperature. This platform provides a pathway to low‐grade thermal energy harvesting. It also enables low‐energy driven thermal artificial robotics, ultrasensitive thermal sensors, and remote controlled near infrared (NIR) driven actuators.
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Abstract The bladder, stomach, intestines, heart, and lungs all move dynamically to achieve their purpose. A long‐term implantable device that can attach onto an organ, sense its movement, and deliver current to modify the organ function would be useful in many therapeutic applications. The bladder, for example, can suffer from incomplete contractions that result in urinary retention with patients requiring catheterization. Those affected may benefit from a combination of a strain sensor and electrical stimulator to better control bladder emptying. The materials and design of such a device made from thin layer carbon nanotube (CNT) and Ecoflex 00–50 are described and demonstrate its function with in vivo feline bladders. During bench‐top characterization, the resistive and capacitive sensors exhibit stability throughout 5000 stretching cycles under physiology conditions. In vivo measurements with piezoresistive devices show a high correlation between sensor resistance and volume. Stimulation driven from platinum‐silicone composite electrodes successfully induce bladder contraction. A method for reliable connection and packaging of medical grade wire to the CNT device is also presented. This work is an important step toward the translation of low‐durometer elastomers, stretchable CNT percolation, and platinum‐silicone composite, which are ideal for large‐strain bioelectric applications to sense or modulate dynamic organ states.
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Abstract Planar, 1D photonic crystals (1D‐PCs) are stacks of alternating layers with different refractive indices, which can reflect specific wavelengths of light through the formation of a photonic bandgap. Typical systems for 1D‐PC fabrication possess relatively limited thermal and/or chemical stabilities and may require several steps for producing patterned features. Additionally, enabling stimuli‐responsive behaviors in 1D‐PCs are often achieved through relatively complex chemistries that might be difficult to scale‐up due to associated cost and energy consumption, presenting challenges toward their implementation in practical systems. Herein, through sequential depositions of phenolic resin (resol) and poly(vinylidene fluoride‐
co ‐hexafluoropropylene) (PVDF‐HFP), two low‐cost chemical reagents which are broadly used in industry, bright 1D‐PCs are prepared with high thermal and chemical stability at long exposure times. Furthermore, spatial differences in the reflectance behavior of the 1D‐PCs and thus resulted patterns are demonstrated through a simple, generalizable interfacial engineering approach that controls the surface wettability of PVDF‐HFP layer. Stimuli‐responsive behavior is imparted into the 1D‐PC system by leveraging the semicrystalline nature of PVDF‐HFP to provide on‐demand switchable light‐reflecting behaviors upon exposure to elevated temperatures. Overall, this work demonstrates a simple and efficient technique to develop 1D‐PCs with excellent stability, ease of patterning, and thermoresponsive reflectance from low‐cost precursors, potentially enabling their broader use in a wide array of nanotechnological applications. -
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Materials that can be switched between low and high thermal conductivity states would advance the control and conversion of thermal energy. Employing in situ time-domain thermoreflectance (TDTR) and in situ synchrotron X-ray scattering, we report a reversible, light-responsive azobenzene polymer that switches between high (0.35 W m−1K−1) and low thermal conductivity (0.10 W m−1K−1) states. This threefold change in the thermal conductivity is achieved by modulation of chain alignment resulted from the conformational transition between planar (
trans ) and nonplanar (cis ) azobenzene groups under UV and green light illumination. This conformational transition leads to changes in the π-π stacking geometry and drives the crystal-to-liquid transition, which is fully reversible and occurs on a time scale of tens of seconds at room temperature. This result demonstrates an effective control of the thermophysical properties of polymers by modulating interchain π-π networks by light.
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Accepted Manuscript1.0
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