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Harvesting of photosynthetic electrons (PEs) from photosynthetic cells or isolated photosynthetic apparatus holds great prospects for environmentally friendly energy generation. However, the low current output and power density still remain significant challenges. Here, we propose highly porous MnO2-decorated 3D-printed graphene electrodes that enhance thylakoid adhesion, PE extraction and storage and dramatically increase areal PE current density. With optimized graphene oxide (GO) hydrogel inks composed of GO, hydroxypropyl methylcellulose (HPMC) and Carbomer 940, GO microlattices are 3D printed and thermally reduced to highly porous 3D graphene electrodes. Among different deposition methods, potentiodynamic electrodeposition of MnO2 onto the electrode surface results in both the highest porosity and largest surface area. MnO2 facilitates the firm adhesion of thylakoid membranes (TMs) and down-shifts the mid potential for more favorable oxidation of PE carriers in photosynthetic apparatuses. With these enhancements, a 3D MnO2-graphene electrode achieves a 50 fold higher capacitance (304 F g−1) than bare graphene electrodes. When TMs are coated, PE current density dramatically improves by 30 fold (580 μA cm−2) compared to PE current from bare graphene electrodes. Finally, full cell tests demonstrated light-triggered self-charging performances with an OCV of 333 mV and produced a power density of up to 930 mW m−2. [ABSTRACT FROM AUTHOR]

Rapid advances in 3D printing enable the construction of complex metal structures. However, sensor embedding within 3D printed metal structures has been challenging due to its extremely high-temperature condition. Here, we embedded an optical fibre sensor for temperature monitoring within a Ni-alloy miniature turbine blade by directed energy deposition (DED) printing. To endure the high-temperature condition, a fibre Bragg grating (FBG) sensor was electroplated with a Ni layer, and various 3D printing parameters were optimised. In particular, to minimise the accumulation of thermal energy in the FBG sensor, 'line-by-line printing and stop' process was applied around the sensor. The embedded sensor accurately measured temperature cycling up to 500°C with the sensitivities of 28.3 and 27.2 pm/K in heating and cooling cycles, respectively. Finally, an FBG sensor was successfully embedded in a miniature turbine blade by our DED process, demonstrating its feasibility for high-temperature monitoring. [ABSTRACT FROM AUTHOR]

The rapid detection of biomolecule levels in the human body is often required to monitor human health. Although swellable microneedle arrays are widely used to extract biomolecules in interstitial fluid in a minimally invasive manner, it takes 3–15 min to carry this out. Herein, we report the development of a microneedle sensor system for the rapid detection of biomolecules. By controlling the crosslinking sequence of methacrylated hyaluronic acid (MeHA) used in the microneedle array, we achieve a swelling ratio of approximately 600% in 30 s in vitro. Furthermore, an electrochemical measurement method is utilized to detect redox reaction of biomolecules extracted with the MeHA microneedle array and screen‐printed electrode. One can measure 1 × 10−6m of dopamine in 3 s in vitro and with excellent selectivity in a solution of dopamine along with 100 × 10−6m of L‐ascorbic acid and uric acid. Finally, ex vivo electrochemical analysis is performed on a gelatin phantom and porcine skin containing various concentrations of dopamine and can detect 10 × 10−6m of dopamine within 30 s. Thus, the swellable hydrogel‐based microneedle array can be applied to biomolecule sensing in interstitial fluid within a few seconds. [ABSTRACT FROM AUTHOR]

Photosynthesis converts solar energy to electricity in a highly efficient manner. Since only water is needed as fuel for energy conversion, this highly efficient energy conversion process has been rigorously investigated. In particular, photosynthetic apparatus, such as photosystem II (PSII), photosystem I (PSI), or thylakoids, have been isolated from various plants to construct bio-hybrid anodes. Although PSII or PSI decorated anodes have shown potentials, there still remain challenges, such as poor stability of PSII-based systems or need for electron donors other than water molecules of PSI-based systems. Thylakoid membranes are relatively stable after isolation and they contain all the necessary photosynthetic apparatus including the PSII and PSI. To increase electrical connections between thylakoids and anodes, nanomaterials such as carbon nanotubes, nanowires, nanoparticles, or graphene have been employed. However, since they rely on the secondary electrical connections between thylakoids and anodes; it is desired to achieve larger direct contacts between them. Here, we aimed to develop micro-pillar (MP) array anodes to maximize direct contact with thylakoids. The thylakoid morphology was analyzed and the MP array was designed to maximize direct contact with thylakoids. The performance of MP anodes and a photosynthetic fuel cell based on MP electrodes was demonstrated and analyzed. [ABSTRACT FROM AUTHOR]