Double-network tough hydrogels have raised increasing interest in stretchable electronic applications as well as electronic skin (e-skin) owing to their excellent mechanical properties and functionalities. While hydrogels have been extensively explored as solid-state electrolytes, stretchable energy storage devices based on tough hydrogel electrolytes are still limited despite their high stretchability and strength. A key challenge remains in the robust electrode/electrolyte interface under large mechanical strains. Inspired by the skin structure that involves the microstructured interface for the tight connection between the dermis and epidermis, we demonstrated that a surface-microstructured tough hydrogel electrolyte composed of agar/polyacrylamide/LiCl (AG/PAAm/LiCl) could be exploited to allow stretchable supercapacitors with enhanced mechanical and electrochemical performance. The prestretched tough hydrogel electrolyte was treated to generate surface microstructures with a roughness of tens of micrometers simply via mechanical rubbing followed by the attachment of activated carbon electrodes on both sides to realize the fabrication of the stretchable supercapacitor. Through investigating the properties of the tough hydrogel electrolyte and the electrochemical performance of the as-fabricated supercapacitors under varied strains, the surface-microstructured hydrogel electrolyte was shown to enable robust adhesion to electrodes, improving electrochemical behavior and capacitance, as well as having better performance retention under repeated stretching cycles, which surpassed the pristine hydrogel with smooth surfaces. Our approach could provide an alternative and general strategy to improve the interfacial properties between the electrode and the hydrogel electrolyte, driving new directions for functional stretchable devices based on tough hydrogels.

Highly compact lasers with ultra-low threshold and single-mode continuous wave (CW) operation have been a long sought-after component for photonic integrated circuits (PICs). Photonic bound states in the continuum (BICs), due to their excellent ability of trapping light and enhancing light-matter interaction, have been investigated in lasing configurations combining various BIC cavities and optical gain materials. However, the realization of BIC laser with a highly compact size and an ultra-low CW threshold has remained elusive. We demonstrate room temperature CW BIC lasers in the 1310 nm O-band wavelength range, by fabricating a miniaturized BIC cavity in an InAs/GaAs epitaxial quantum dot (QD) gain membrane. By enabling effective trapping of both light and carriers in all three dimensions, ultra-low threshold of 12 μW (0.052 kW cm−2) is achieved at room temperature. Single-mode lasing is also realized in cavities as small as only 5 × 5 unit cells (~2.5 × 2.5 μm2 cavity size) with a mode volume of 1.16(λ/n)3. The maximum operation temperature reaches 70 °C with a characteristic temperature of T0 ~93.9 K. With its advantages in terms of a small footprint, ultra-low power consumption, and adaptability for integration, the mini-BIC lasers offer a perspective light source for future PICs aimed at high-capacity optical communications, sensing and quantum information.

The combination of grating-based frequency-selective optical feedback mechanisms, such as distributed feedback (DFB) or distributed Bragg reflector (DBR) structures, with quantum dot (QD) gain materials is a main approach towards ultrahigh-performance semiconductor lasers for many key novel applications, as either stand-alone sources or on-chip sources in photonic integrated circuits. However, the fabrication of conventional buried Bragg grating structures on GaAs, GaAs/Si, GaSb, and other material platforms has been met with major material regrowth difficulties. We report a novel and universal approach of introducing laterally coupled dielectric Bragg gratings to semiconductor lasers that allows highly controllable, reliable, and strong coupling between the grating and the optical mode. We implement such a grating structure in a low-loss amorphous silicon material alongside GaAs lasers with InAs/GaAs QD gain layers. The resulting DFB laser arrays emit at pre-designed 0.8 THz local area network wavelength division multiplexing frequency intervals in the 1300 nm band with record performance parameters, including sidemode suppression ratios as high as 52.7 dB, continuous-wave output power of 26.6 mW (room temperature) and 6 mW (at 55°C), and ultralow relative intensity noise (RIN) of < − 165    dB / Hz (2.5–20 GHz). The devices are also capable of isolator-free operating under very high external reflection levels of up to − 12.3    dB while maintaining high spectral purity and ultralow RIN qualities. These results validate the novel laterally coupled dielectric grating as a technologically superior and potentially cost-effective approach for fabricating DFB and DBR lasers free of their semiconductor material constraints, which are thus universally applicable across different material platforms and wavelength bands.

Dehydroabietyl polyethylene glycol glycidyl ether-grafted hydroxyethyl cellulose (HEC) polymer surfactant (DA (EO) 5 GE-g-HEC) was prepared using ring-opening polymerization with biobased rosin and hydroxyethyl cellulose as feedstocks. Dehydroabietyl polyethylene glycol glycidyl ether (DA(EO) 5 GE) was formed by condensation of dehydroabietyl alcohol polyoxyethylene ether (Rosin derivative: DA(EO) 5 H) and epichlorohydrin. The grafting degree of DA(EO) 5 GE-g-HEC was manipulated by adjusting the mass ratio of HEC and DA(EO) 5 GE and confirmed by EA. According to the formula, when m (HEC) /m (DA(EO)2GE) was 1:1~1:5, the grafting rate of DA(EO) 5 GE in DA(EO) 5 GE-g-HEC varied from 34.43% to 38.33%. The surface activity and foam properties of DA(EO) 5 GE-g-HEC aqueous solution were studied. The results showed that with the increase in grafting rate, the critical micellar concentration (CMC) in aqueous solution changed from 1.28 to 0.96 g/L. The results of the thermogravimetric analysis showed that the temperature range of the main stage of mass loss of DA(EO) 5 GE-g-HEC was 310°C~410°C, and the thermal decomposition processes of the samples with five mass ratios were similar. An oil in water emulsion was prepared by choosing cyclohexane as the oil phase and DA(EO) 5 GE-g-HEC as the emulsifier. The effect of DA(EO) 5 GE-g-HEC mass fraction on emulsion particle size and stability was analyzed. The results suggested that when the oil-water ratio was 8:2 with 0.4% emulsifier, the emulsion droplets were the smallest in terms of particle size and were the most stable. The rheological test results showed that the apparent viscosity decreased with the increase in shear rate and showed a typical elastic gel phenomenon.

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