Chensha Li

Dye‐Sensitized Solar Cell with Energy Storage Function through PVDF/ZnO Nanocomposite Counter Electrode

Dye-sensitized solar cells with an energy storage function are demonstrated by modifying its counter electrode with a poly (vinylidene fluoride)/ZnO nanowire array composite. This simplex device could still function as an ordinary solar cell with a steady photocurrent output even after being fully charged. An energy storage density of 2.14 C g(-1) is achieved, while simultaneously a 3.70% photo-to-electric conversion efficiency is maintained.

Actuators based on liquid crystalline elastomer materials

Liquid crystalline elastomers (LCEs) exhibit a number of remarkable physical effects, including the unique, high-stroke reversible mechanical actuation when triggered by external stimuli. This article reviews some recent exciting developments in the field of LCE materials with an emphasis on their utilization in actuator applications. Such applications include artificial muscles, industrial manufacturing, health and microelectromechanical systems (MEMS). With suitable synthetic and preparation pathways and well-controlled actuation stimuli, such as heat, light, electric and magnetic fields, excellent physical properties of LCE materials can be realized. By comparing the actuating properties of different systems, general relationships between the structure and the properties of LCEs are discussed. How these materials can be turned into usable devices using interdisciplinary techniques is also described.

Reversible white-light actuation of carbon nanotube incorporated liquid crystalline elastomer nanocomposites†

We present single-wall carbon nanotube (SWCNT) incorporated liquid crystal elastomer (LCE) nanocomposites that demonstrate strong, reversible photoactuation. The matrix nematic LCE material possesses reversible thermal deformation, while SWCNTs perform photothermal energy conversion and local heat dissipation upon irradiation. The resultant SWCNT–LCE nanocomposites exhibit effective photoactuation not only by infrared (IR) irradiation, but also white light with an intensity on the order of 100 mW cm−2. Rapid and reversible photo-induced strain was observed. The nanocomposite films contracted up to one third of the original length in several seconds under the irradiation of white light, and recovered to the original length in several seconds after the light source was switched off. Moreover, the nematic–isotropic transition temperatures of the SWCNT–LCE nanocomposites were evidently lower than that of the blank LCE by up to 19 °C.

Synthesis of a photoresponsive liquid-crystalline polymer containing azobenzene.

The synthesis of an oriented liquid-crystalline photoresponsive polymer, prepared by polymerization of mono- and di-acrylates, both of which contain azobenzene chromophores, is reported. The prepared free-standing polymer film shows strong reversible photoinduced deformation upon exposure to unpolarized UV light at 366 nm, as a result of an optically induced isomeric change of the azobenzene moieties in the polymer network. The synthesis process is relatively simple and more efficient compared to conventional ones, and can be used to synthesize other liquid-crystalline photoresponsive polymers. The use of this photoresponsive polymer film as an optical high-pass/low-pass switch under UV or natural light irradiation for a laser beam is demonstrated. This photoresponsive polymer may have applications in robotic systems, artificial muscles, and actuators in microelectromechanical systems (MEMS) and labs on chips.

Direct solar energy conversion and storage through coupling between photoelectrochemical and ferroelectric effects

Harvesting and storing solar energy has become more and more important. Current solid-state photovoltaic cells and conventional photoelectrochemical cells are not capable of directly storing the converted energy, which has to be facilitated by connecting to external storing devices. We demonstrate a device architecture that can convert and store solar energy in the electrical form within an intrinsically single structure. Mobile charge is internally stored, based on the coupling between photoelectrochemical and ferroelectric effects. The tested device architecture can be photo-charged under 1000 W/m2 of white light to an open-circuit voltage of 0.47V with a capacity of 37.62 mC/cm2. After removal of the light source, the mobile charge stored lasts more than 8 hours, and the open-circuit output voltage lasts more than 24 hours.

Light Actuation of Graphene-Oxide Incorporated Liquid Crystalline Elastomer Nanocomposites

The authors demonstrate high-performance photo-actuation of nematic liquid crystal elastomer (LCE) nanocomposites incorporating graphene oxide (GO). The nematic LCE serves as the matrix with reversible thermomechanical response. The incorporated GO absorbs photons and converts the photonic energy to heat, thus actuating the LCE nanocomposite. Both infrared and visible lights of wide spectrum (white light) or various wavelength ranges irradiations are able to effectively actuate the LCE nanocomposites, thus proves that they can fully utilize the photo energy of a light source for their mechanical actuation. Attributed to the well dispersity of GO in LCE matrix, sensitive (in seconds) and reversible photo-induced strain of LCE nanocomposites with consistent shape-changing ratio and significantly enhanced mechanical properties are observed. The contraction of the LCE nanocomposite films under light irradiation is about one third of the original length. The effective load-actuation capability is elevated about 50%.

Reversible Photo Actuated Bulk Nanocomposite with Nematic Liquid Crystalline Elastomer Matrix

Liquid crystal elastomers (LCEs) are excellent actuator materials. However, current LCE materials are generally made in the forms with thin thickness, such as films or fibers, which have limitations in forming actuators. We have developed a bulk LCE material with the three-dimensional elastic skeleton network of polyurethane and the matrix of nematic LCE incorporating single-wall carbon nanotubes (SWCNTs). This LCE nanocomposite bulk (LCENB) exhibited sensitive and reversible photo actuation. It could evenly contract by up to 25% of the initial height under a uniform irradiation, or bend towards the incident light by up to 40° under an asymmetrical irradiation. A photo-driven scanning mirror with superior scanning angle, implementing this LCENB as the actuator, was also demonstrated.

Autonomous passive light tracking utilizing single-wall carbon nanotube enhanced opto-thermo-mechanical elastomer actuators

We have developed novel opto-thermo-mechanical actuators by effectively distributing a significant amount of single-wall carbon nanotube (SWCNT, up to 0.7%w/w) into liquid crystal elastomer (LCE) matrices. These SWCNT/LCE actuators exhibit a great potential to be utilized in MEMS applications, as they respond to a wide spectrum of visible/near-infrared light, and possess a large reversible compressive strain (up to 35%) when stimulated. Autonomous and passive light tracking is demonstrated here as one of the applications. With a simple design, the actuators are able to adaptively tilt a solar cell towards the light source by a degree of ∼15° (with an incident light intensity of 1.6 kW/m2). As a result, the photocurrent output of the solar cell is significantly enhanced (up to 247.10%) without any other control system or external energy source.

Two-step crosslinked liquid-crystalline elastomer with reversible two-way shape memory characteristics

ABSTRACT Liquid-crystalline elastomers (LCEs) possess large and equilibrium reversible anisotropic dimensional change in response to applied stimuli. The deformation behavior demonstrated by current LCE materials under the stimuli are generally determined by their own geometries and the alignment distributions of liquid crystal (LC) units in the LCE matrices. Here we report a LCE whose synthesis was through a two-stage crosslinking coupled with a mechanical reshaping process, where the shape was mechanically reset before the final crosslinking. It demonstrated reversible memory and change between the initial geometries formed during the first crosslinking stage and any reshaped geometries under the stimuli. Its deformation is not influenced by the geometries and the alignment distributions of LC units in the LCE matrix. This characteristic in LCEs holds promise in a wide range of application researches requiring sophisticated functions and smart structures.

A microfluidic sensor of Botulinum neurotoxin type a utilizing SNAP-25 incorporated responsive hydrogel

Clostridium Botulinum neurotoxins (BoNTs) are the most lethal bacterial toxins known to humankind in nature. They present grave bioterrorism concern, especially within food supplies. The current pharmacotoxicological mouse bioassay accepted for detection of BoNT in food is laborious and expensive, lacks specificity, or may cause false alarm. It is highly desired to develop a rapid and sensitive on-site toxin-screening vehicle for the detection of BoNT. We developed a prototype microfluidics-based BoNT sensor based on our newly synthesized photo-patternable hydrogel, which was polymerized with a modified peptide containing crosslinker incorporating the synaptosome-associated protein SNAP-25 peptide specifically responsive to serotype A of BoNT, or BoNT/A. The cleavage caused by BoNT/A provided an easily observable change in the hydrogel patterns. Hydrogel structures were photo-patterned in a microfluidic channel. These hydrogels were compromised and cleaved in 100 mg/ml of trypsin after 4 hours, and in a solution containing the light chain (LC) of BoNT/A (concentration: 45 μg/mL) in 38 hours. In the control experiments, the same hydrogels were intact in Hepes buffer (30mM).