Oriented liquid crystal networks (LCNs) can undergo reversible shape change at the macroscopic scale upon an order–disorder phase transition of the mesogens. This property is explored for developing ...soft robots that can move under external stimuli, such as light in most studies. Herein, electrically driven soft robots capable of executing various types of biomimetic locomotion are reported. The soft robots are composed of a uniaxially oriented LCN strip, a laminated Kapton layer, and thin resistive wires embedded in between. Taking advantage of the combined attributes of the actuator, namely, easy processing, reprogrammability, and reversible shape shift between two 3D shapes at electric power on and off state, the concept of a “Janus” soft robot is demonstrated, which is built from a single piece of the material and has two parts undergoing opposite deformations simultaneously under a uniform stimulation. In addition to complex shape morphing such as the movement of oarfish and sophisticated devices like self‐locking grippers, electrically powered “Janus” soft robots can accomplish versatile locomotion modes, including crawling on flat surfaces through body arching up and straightening down, crawling inside tubes through body stretching and contraction, walking like four‐leg animals, and human‐like two‐leg walking while pushing a load forward.
Soft robots based on liquid crystal polymers are built to possess two parts capable of simultaneous and opposite deformations upon an order–disorder phase transition. This design enables various electrically powered locomotion modes, including moving on flat surface through body arching up–straightening down, crawling in a tunnel‐like tube through body stretching–contraction, four‐leg walking, and two‐leg walking while pushing a load.
The ability to optically reconfigure an existing actuator of a liquid crystal polymer network (LCN) so that it can display a new actuation behavior or function is highly desired in developing ...materials for soft robotics applications. Demonstrated here is a powerful approach relying on selective polymer chain decrosslinking in a LCN actuator with uniaxial LC alignment. Using an anthracene‐containing LCN, spatially controlled optical decrosslinking can be realized through photocleavage of anthracene dimers under 254 nm UV light, which alters the distribution of actuation (crosslinked) and non‐actuation (decrosslinked) domains and thus determines the actuation behavior upon order‐disorder phase transitions. Based on this mechanism, a single actuator having a flat shape can be reconfigured in an on‐demand manner to exhibit reversible shape transformation such as self‐folding into origami three‐dimensional structures. Moreover, using a dye‐doped LCN actuator, a light‐fueled microwalker can be optically reconfigured to adopt different locomotion behaviors, changing from moving in the laser scanning direction to moving in the opposite direction.
Walk along: Selective polymer chain decrosslinking in a liquid crystal polymer network (LCN) actuator is demonstrated. Spatially controlled optical decrosslinking alters the distribution of the actuation (crosslinked) and non‐actuation (decrosslinked) domains, and determines the actuation behavior upon the order–disorder phase transition. By using a dye‐doped LCN actuator, a light‐fueled microwalker can be optically reconfigured.
Novel main‐chain liquid crystalline Diels—Alder dynamic networks (LCDANs) were prepared that exhibit unprecedented ease for actuator programming and reprocessing compared to existing liquid ...crystalline network (LCN) systems. Following cooling from 125 °C, LCDANs are deformed with aligned mesogens self‐locked at room temperature by slowly formed Diels–Alder (DA) bonds, which allows for the formation of solid 3D actuators capable of reversible shape change, and strip walker and wheel‐capable light‐driven locomotion upon either thermally or optically induced order–disorder phase transition. Any actuator can readily be erased at 125 °C and reprogrammed into a new one under ambient conditions. Moreover, LCDANs can be processed directly from melt (for example, fiber drawing) and from solution (for example, casting tubular actuators), which cannot be achieved with LCNs using exchangeable covalent bonds. The combined attributes of LCDANs offer significant progress toward developing easily programmable/processable LCN actuators.
Liquid crystalline dynamic networks can be shaped into 3D objects at room temperature while being stabilized by slowly formed Diels–Alder‐bonded (DA) cross‐links. The actuators demonstrate thermally or optically induced reversible shape change for the purpose of performing mechanical work or locomotion.
The Yellow River (Huanghe) submerged delta (YRSD) has been under the threat of erosion and retreat during the Anthropocene due to dramatic climatic and anthropogenic changes in the Yellow River ...basin. The analysis of field data shows that over the period of 1977–2005, the changes in climate (decrease in precipitation and increase in air temperature) and human interventions (increase in water diversion projects) throughout the watershed have resulted in the sharp reductions of river flow and sediment discharges into the Bohai Sea. Consequently, over the decadal timescale, morphological evolution of the YRSD has gone through three stages: i.e. rapid accumulation (5.77×108m3/year) in 1977–1985, moderate accumulation (3.80×108m3/year) in 1986–1995 and slow accumulation (0.91×108m3/year) in 1996–2005. Climatic change within the catchment characterized by the rapid increase of air temperature contributed significantly to the transitions from the rapid accumulation to the moderate accumulation, and to the subsequent slow accumulation. The decadal morphological changes of the YRSD also show peculiar deposition/erosion characteristics over the medium timescale under river input reduction. Within the three decades, the patterns of the main sedimentary body exhibit irregular ellipses with the long axis parallel to the −5 or −10m isobaths and short axis perpendicular to the isobaths. The depocentres of the YRSD are located between the −10 and −15m isobaths close to the respective river mouths, with a high vertical accretion rate of ~1.20m/year. The time series data of annual volumetric change of the YRSD and river sediment load from 1977 to 2005 further demonstrate significant linear positive relationships between deltaic geomorphic change and fluvial input over shorter timescales (annual and 3-year). The critical sediment discharges for maintaining the deposition/erosion equilibrium state of the YRSD over the annual and 3-year timescales are found to be 1.79×108t/year and 1.29×108t/year, respectively. The analysis from the latest hydrological data (2006–2015) suggests that over the decadal timescale, the evolution state of the YRSD currently has transitioned from constructive to destructive due to the weakened fluvial input. Moreover, there exists a close quantitative link between the progradation of the Yellow River subaerial delta (YRAD) and the YRSD over the five-year timescale, indicating that every 1×108m3/year increase of the YRSD's yearly volumetric change will result in a 3.28km2/year increase of the YRAD's yearly land-accretion area, and the YRAD will reach the extension/retreat balance state when yearly morphological change of the YRSD is at 0.73×108m3/year.
•The Yellow River Submerged Delta (YRSD) has successively went through rapid, moderate and slow accumulation stages during 1976-2005.•Stage transition is strongly associated with climate-induced fluvial supply decrease.•The YRSD’s depocenter maintains a high-rate of deposition under river input reduction.•Evolution state of the YRSD currently has transitioned from constructive to destructive.•A clear link exists between the progradation of the subaerial and submerged deltas.
Liquid crystalline network (LCN) actuator normally deforms upon thermally or optically induced order-disorder phase transition, switching once between two shapes (shape 1 in LC phase and shape 2 in ...isotropic state) for each stimulation on/off cycle. Herein, we report an LCN actuator that deforms from shape 1 to shape 2 and then reverses the deformation direction to form shape 3 on heating or under light only, thus completing the shape switch twice for one stimulation on/off cycle. The deformation reversal capability is obtained with a monolithic LCN actuator whose two sides are made to start deforming at different temperatures and exerting different reversible strains, by means of asymmetrical crosslinking and/or asymmetrical stretching. This desynchronized actuation strategy offers possibilities in developing light-fueled LCN soft robots. In particular, the multi-stage bidirectional shape change enables multimodal, light-driven locomotion from the same LCN actuator by simply varying the light on/off times.
Soft actuators based on liquid crystal polymer networks (LCNs) have emerged as an exciting research topic due to many envisioned applications in areas such as soft robotics and self‐regulating ...devices. The infatuation stems from the amazing ability of LCNs to display reversible, large amplitude, and complex shape change as well as locomotion upon a stimuli‐triggered phase transition of mesogens between ordered liquid crystal and disordered isotropic state. Among the various stimuli, light arguably is the most attractive choice. Light can easily be adjusted for its wavelength, intensity, or polarization, structured by means of photomasks or interference patterns, and applied to a target remotely and with high spatiotemporal resolution. Indeed, much research effort is dedicated to LCN actuators that are designed to respond to light in many ways, with light being used not only as an external energy source to drive the shape changes or motion of LCN actuators, but also as a versatile tool in their fabrication and reconfiguration. In this Review, recent achievements are highlighted, a number of important issues are discussed, and critical analysis on the use of light in making, reconfiguring, and driving LCN actuators is provided.
Light plays a key role in the development of soft actuators based on liquid crystal polymer networks (LCNs). In this Review, the use of light for their fabrication, reconfiguration, and motion driving is highlighted and analyzed, a number of challenging issues are discussed, and an outlook on the future development is presented.
To collect data of randomised controlled trials (RCTs) and clinical controlled trials (CCTs) for evaluating the effects of enhanced recovery after surgery on postoperative recovery of patients who ...received total hip arthroplasty (THA) or total knee arthroplasty (TKA).
Relevant, published studies were identified using the following key words: arthroplasty, joint replacement, enhanced recovery after surgery, fast track surgery, multi-mode analgesia, diet management, or steroid hormones. The following databases were used to identify the literature consisting of RCTs or CCTs with a date of search of 31 December 2016: PubMed, Cochrane, Web of knowledge, Ovid SpringerLink and EMBASE. All relevant data were collected from studies meeting the inclusion criteria. The outcome variables were postoperative length of stay (LOS), 30-day readmission rate, and total incidence of complications. RevMan5.2. software was adopted for the meta-analysis.
A total of 10 published studies (9936 cases) met the inclusion criteria. The cumulative data included 4205 cases receiving enhanced recovery after surgery (ERAS), and 5731 cases receiving traditional recovery after surgery (non-ERAS). The meta-analysis showed that LOS was significantly lower in the ERAS group than in the control group (non-ERAS group) (p<0.01), and there were fewer incidences of complications in the ERAS group than in the control group (p=0.03). However, no significant difference was found in the 30-day readmission rate (p=0.18).
ERAS significantly reduces LOS and incidence of complications in patients who have had THA or TKA. However, ERAS does not appear to significantly impact 30-day readmission rates.
Trimethylation of histone H3 on lysine-4 (H3K4me3) is associated with gene-regulatory elements, but its transcription-independent function in cell division is unclear. CxxC-finger protein-1 (CFP1) is ...a major mediator of H3K4 trimethylation in mouse oocytes. Here we report that oocyte-specific knockout of Cxxc1, inhibition of CFP1 function, or abrogation of H3K4 methylation in oocytes each causes a delay of meiotic resumption as well as metaphase I arrest owing to defective spindle assembly and chromosome misalignment. These phenomena are partially attributed to insufficient phosphorylation of histone H3 at threonine-3. CDK1 triggers cell division-coupled degradation and inhibitory phosphorylation of CFP1. Preventing CFP1 degradation and phosphorylation causes CFP1 accumulation on chromosomes and impairs meiotic maturation and preimplantation embryo development. Therefore, CFP1-mediated H3K4 trimethylation provides 3a permission signal for the G2-M transition. Dual inhibition of CFP1 removes the SETD1-CFP1 complex from chromatin and ensures appropriate chromosome configuration changes during meiosis and mitosis.
Ferroelectric (FE) materials, including BiFeO3, P(VDF‐TrFE), and CuInP2S6, are a type of dielectric material with a unique, spontaneous electric polarization that can be reversed by applying an ...external electric field. The combination of FE and low‐dimensional materials produces synergies, sparking significant research interest in solar cells, photodetectors (PDs), nonvolatile memory, and so on. The fundamental aspects of FE materials, including the origin of FE polarization, extrinsic FE materials, and FE polarization quantification are first discussed. Next, the state‐of‐the‐art of FE‐based optoelectronic devices is focused. How FE materials affect the energy band of channel materials and how device structures influence PD performance are also summarized. Finally, the future directions of this rapidly growing field are discussed.
For the development of ferroelectric (FE)‐based optoelectronic devices, a better understanding of the fundamental properties of FE materials, quantification of FE polarization, and interface study of heterostructures between FE/low‐dimensional (LD) materials are of great importance. This review summarizes recent developments and challenges in FE‐enhanced LD optoelectronic devices.
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