Data_Sheet_1_Effects of antioxidants on physicochemical properties and odorants in heat processed beef flavor and their antioxidant activity under different storage conditions.pdf

Heat processed beef flavor (HPBF) is a common thermal process flavoring, whose flavor properties can be affected by lipid oxidation during storage. Addition of antioxidants is an option to avoid the changes of HPBF induced by lipid oxidation. In this study, the effects of three antioxidants, tert-butylhydroquinone (TBHQ), tea polyphenol (TP), and L-ascorbyl palmitate (L-AP), on volatile components, physicochemical properties, and antioxidant activities of HPBF were studied over 168 days at different temperatures (4, 20, and 50°C). Although all three antioxidants had little effect on browning, acidity, water activity, and secondary lipid oxidation products, L-AP and TBHQ showed greater capabilities to prevent the formation of primary lipid oxidation products than TP. According to the results of oxidation reduction potential and DPPH radical scavenging experiments, TBHQ had better antioxidant ability compared to L-AP and TP during the storage. Of note, TBHQ affected the flavor profiles of HPBF, mainly on volatile odorants produced by lipid degradation. TBHQ could mitigate the development of unfavorable odorants. This study indicated TBHQ would enhance lipid oxidation stability and maintain physicochemical properties and flavor profiles of HPBF during storage. It suggested that TBHQ could be applied as an alternative additive to improve the quality of HPBF related thermal process flavorings.</p

Controlled Free Edge Effects in Surface Wrinkling via Combination of External Straining and Selective O₂ Plasma Exposure

Herein the edge effect from the traction-free boundary condition is utilized to direct the spontaneous surface wrinkling. This boundary condition is attained by a simple combination of mechanical straining and selective exposure of polydimethylsiloxane (PDMS) substrate to O₂ plasma (OP) through a copper grid. When the strained PDMS sheet is subjected to selective OP treatment, a patterned heterogeneous surface composed of the OP-exposed “hard” oxidized SiO_<i>x</i> region (denoted as <i>D</i>₁) and the OP-unexposed “soft” region (denoted as <i>D</i>₂) is produced. The subsequent full release of the prestrain (ε_pre) leads to the selective wrinkling in <i>D</i>₁, rather than in <i>D</i>₂. It is seen that even in <i>D</i>₁, no wrinkling occurs in the vicinity of the <i>D</i>₁ edge that is perpendicular to the wavevector. Furthermore, the average wrinkle wavelength in <i>D</i>₁ (λ_<i>D</i>1) is smaller than that of the exposed copper grid-free blank area (λ_blank). This wavelength decrement between λ_<i>D</i>1 and λ_blank, which can be used to roughly estimate the edge-effect extent, increases with the applied mesh number of copper grids and exposure duration, while decreases with the increase of ε_pre. Meanwhile, there exists a decrease in the amplitude of the patterned wrinkles, when compared with that of the blank region. Additionally, hierarchical wrinkling is induced when the strain-free PDMS substrate is selectively exposed to OP, followed by uniaxial stretching and the subsequent blanket exposure. Consequently, oriented wrinkles perpendicular to the stretching direction are generated in <i>D</i>₂. With respect to <i>D</i>₁, no wrinkling happens or orthogonal wrinkles occur in this region depending on the applied mesh number, exposure duration, and ε_pre. In the above wrinkling process, the combinative edge effects in two perpendicular directions that are involved sequentially have been discussed

Highly Crumpled All-Carbon Transistors for Brain Activity Recording

Neural probes based on graphene field-effect transistors have been demonstrated. Yet, the minimum detectable signal of graphene transistor-based probes is inversely proportional to the square root of the active graphene area. This fundamentally limits the scaling of graphene transistor-based neural probes for improved spatial resolution in brain activity recording. Here, we address this challenge using highly crumpled all-carbon transistors formed by compressing down to 16% of its initial area. All-carbon transistors, chemically synthesized by seamless integration of graphene channels and hybrid graphene/carbon nanotube electrodes, maintained structural integrity and stable electronic properties under large mechanical deformation, whereas stress-induced cracking and junction failure occurred in conventional graphene/metal transistors. Flexible, highly crumpled all-carbon transistors were further verified for in vivo recording of brain activity in rats. These results highlight the importance of advanced material and device design concepts to make improvements in neuroelectronics

Highly Sensitive Wearable Pressure Sensors Based on Three-Scale Nested Wrinkling Microstructures of Polypyrrole Films

Pressure sensors have a variety of applications including wearable devices and electronic skins. To satisfy the practical applications, pressure sensors with a high sensitivity, a low detection limit, and a low-cost preparation are extremely needed. Herein, we fabricate highly sensitive pressure sensors based on hierarchically patterned polypyrrole (PPy) films, which are composed of three-scale nested surface wrinkling microstructures through a simple process. Namely, double-scale nested wrinkles are generated via in situ self-wrinkling during oxidative polymerization growth of PPy film on an elastic poly­(dimethylsiloxane) substrate in the mixed acidic solution. Subsequent heating/cooling processing induces the third surface wrinkling and thus the controlled formation of three-scale nested wrinkling microstructures. The multiscale nested microstructures combined with stimulus-responsive characteristic and self-adaptive ability of wrinkling morphologies in PPy films offer the as-fabricated piezoresistive pressure sensors with a high sensitivity (19.32 kPa^–1), a low detection limit (1 Pa), an ultrafast response (20 ms), and excellent durability and stability (more than 1000 circles), these comprehensive sensing properties being higher than the reported results in literature. Moreover, the pressure sensors have been successfully applied in the wearable electronic fields (e.g., pulse detection and voice recognition) and microcircuit controlling, as demonstrated here

Highly Sensitive Wearable Pressure Sensors Based on Three-Scale Nested Wrinkling Microstructures of Polypyrrole Films

Pressure sensors have a variety of applications including wearable devices and electronic skins. To satisfy the practical applications, pressure sensors with a high sensitivity, a low detection limit, and a low-cost preparation are extremely needed. Herein, we fabricate highly sensitive pressure sensors based on hierarchically patterned polypyrrole (PPy) films, which are composed of three-scale nested surface wrinkling microstructures through a simple process. Namely, double-scale nested wrinkles are generated via in situ self-wrinkling during oxidative polymerization growth of PPy film on an elastic poly­(dimethylsiloxane) substrate in the mixed acidic solution. Subsequent heating/cooling processing induces the third surface wrinkling and thus the controlled formation of three-scale nested wrinkling microstructures. The multiscale nested microstructures combined with stimulus-responsive characteristic and self-adaptive ability of wrinkling morphologies in PPy films offer the as-fabricated piezoresistive pressure sensors with a high sensitivity (19.32 kPa^–1), a low detection limit (1 Pa), an ultrafast response (20 ms), and excellent durability and stability (more than 1000 circles), these comprehensive sensing properties being higher than the reported results in literature. Moreover, the pressure sensors have been successfully applied in the wearable electronic fields (e.g., pulse detection and voice recognition) and microcircuit controlling, as demonstrated here

Light-Modulated Surface Micropatterns with Multifunctional Surface Properties on Photodegradable Polymer Films

Photodegradable polymers constitute an emerging class of materials that are expected to possess advances in the areas of micro/nano- and biotechnology. Herein, we report a green and effective strategy to fabricate light-responsive surface micropatterns by taking advantage of photodegradation chemistry. Thanks to the molecular chain breakage during the photolysis process, the stress field of photodegradable polymer-based wrinkling systems undergoes continuous disturbance, leading to the release/reorganization of the internal stress. Revealed by systematic experiments, the light-induced stress release mechanism enables the dynamic adaption of not only thermal-induced labyrinth wrinkles, but uniaxially oriented wrinkle microstructures induced by mechanical straining. This method paves the way for their diverse applications, for example, in optical information display and storage, and the smart fabrication of multifunctional surfaces as demonstrated here

Simple and Versatile Strategy to Prevent Surface Wrinkling by Visible Light Irradiation

A stiff film bonded to a compliant substrate is susceptible to surface wrinkling when it is subjected to in-plane compression. Prevention of surface wrinkling is essential in many cases to maintain the integrity and functionality of this kind of system. Here we report a simple versatile technique to restrain surface wrinkling of an amorphous poly­(<i>p</i>-aminoazobenzene) (PAAB) film by visible light irradiation. The key idea is to use the combined effects of photosoftening of the PAAB film and the stress release induced by the reversible photoisomerization. The main finding given by experiments and dimensional analysis is that the elastic modulus <i>E</i>_f of the film is well modulated by the ratio of light intensity and the release rate, i.e., <i>I</i>/<i>V</i>. Furthermore, the explicit solution describing the correlation of <i>I</i>/<i>V</i> with <i>E</i>_f is derived for the first time. The difference between the calculated critical wrinkling strain ε_c,t based on <i>E</i>_f and the experimentally measured value ε_c enables us to quantitatively evaluate the release amount of the compressive stress in the film. These key solutions provide a simple strategy to prevent the undesired surface wrinkling. Additionally, they allow us to propose a wrinkling-based technique to investigate photoinduced changes in the mechanical properties of azo-containing materials

Simple and Versatile Strategy to Prevent Surface Wrinkling by Visible Light Irradiation

A stiff film bonded to a compliant substrate is susceptible to surface wrinkling when it is subjected to in-plane compression. Prevention of surface wrinkling is essential in many cases to maintain the integrity and functionality of this kind of system. Here we report a simple versatile technique to restrain surface wrinkling of an amorphous poly­(<i>p</i>-aminoazobenzene) (PAAB) film by visible light irradiation. The key idea is to use the combined effects of photosoftening of the PAAB film and the stress release induced by the reversible photoisomerization. The main finding given by experiments and dimensional analysis is that the elastic modulus <i>E</i>_f of the film is well modulated by the ratio of light intensity and the release rate, i.e., <i>I</i>/<i>V</i>. Furthermore, the explicit solution describing the correlation of <i>I</i>/<i>V</i> with <i>E</i>_f is derived for the first time. The difference between the calculated critical wrinkling strain ε_c,t based on <i>E</i>_f and the experimentally measured value ε_c enables us to quantitatively evaluate the release amount of the compressive stress in the film. These key solutions provide a simple strategy to prevent the undesired surface wrinkling. Additionally, they allow us to propose a wrinkling-based technique to investigate photoinduced changes in the mechanical properties of azo-containing materials

Simple and Versatile Strategy to Prevent Surface Wrinkling by Visible Light Irradiation

A stiff film bonded to a compliant substrate is susceptible to surface wrinkling when it is subjected to in-plane compression. Prevention of surface wrinkling is essential in many cases to maintain the integrity and functionality of this kind of system. Here we report a simple versatile technique to restrain surface wrinkling of an amorphous poly­(<i>p</i>-aminoazobenzene) (PAAB) film by visible light irradiation. The key idea is to use the combined effects of photosoftening of the PAAB film and the stress release induced by the reversible photoisomerization. The main finding given by experiments and dimensional analysis is that the elastic modulus <i>E</i>_f of the film is well modulated by the ratio of light intensity and the release rate, i.e., <i>I</i>/<i>V</i>. Furthermore, the explicit solution describing the correlation of <i>I</i>/<i>V</i> with <i>E</i>_f is derived for the first time. The difference between the calculated critical wrinkling strain ε_c,t based on <i>E</i>_f and the experimentally measured value ε_c enables us to quantitatively evaluate the release amount of the compressive stress in the film. These key solutions provide a simple strategy to prevent the undesired surface wrinkling. Additionally, they allow us to propose a wrinkling-based technique to investigate photoinduced changes in the mechanical properties of azo-containing materials

Determinative Surface-Wrinkling Microstructures on Polypyrrole Films by Laser Writing

We report a simple and efficient laser-writing strategy to fabricate hierarchical nested wrinkling microstructures on conductive polypyrrole (PPy) films, which enables us to develop advanced functional surfaces with diverse applications. The present strategy adopts the photothermal effect of PPy films to mimick the formation of hierarchical nested wrinkles observed in nature and design controlled microscale wrinkling patterns. Here, the PPy film is grown on a poly­(dimethylsiloxane) (PDMS) substrate via oxidation polymerization of pyrrole in an acidic solution, accompanied by in situ self-wrinkling with wavelengths of two different scales (i.e., λ₁ and λ₂). Subsequent laser exposure of the PPy/PDMS bilayer induces a new surface wrinkling with a larger wavelength (i.e., λ₃). Owing to the retention of the initial λ₁ wrinkles, we obtain hierarchical nested wrinkles with the smaller λ₁ wrinkles nested in the larger λ₃ ones. Importantly, we realize the large-scale path-determinative fabrication of complex oriented wrinkling microstructures by controlling the relative motion between the bilayer and the laser. Combined with the induced changes in surface color, surface-wrinkling microstructures, and conductivity in the PPy films, the laser-writing strategy can find broad applications, for example, in modulation of surface wetting properties and fabrication of microcircuits, as demonstrated in this work