Significance: Neuroscience studies using optogenetics have greatly improved our understanding of brain circuits. Advances in the combined use of optogenetics and pharmacology to further probe important neurochemical signals has lagged, however, in large part due to the inconvenience of conventional cannulated approaches, as well as the difficulty in controlling, powering, and manufacturing optofluidic devices that are reliable and scalable for distribution to the neuroscience community. Here, we present a battery-free, wireless, lightweight optofluidic device that allows adjustable infusion rates, hands-free operation, and unlimited power supply, and is compatible with existing near-field communication (NFC) technology. We show that this device not only reproduces optogenetic and pharmacological experiments in vivo but, additionally, allows far greater freedom of movement in small animal models compared to existing, comparable platforms.

Narrowband detection of mid-wave infrared is of great importance for many applications including thermal imaging and scientific research. Detection of narrowband signals is typically achieved by using broadband photodetectors combined with interference filters or interferometric optics, which inevitably increase the architectural complexity and transmission loss. Here, we report an uncooled and filterless narrowband photodetector for the detection of mid-wave infrared with an enhanced photoresponse by plasmon resonance. Colloidal HgSe quantum-dot films were employed as sensing materials with narrowband optical absorption due to the intraband 1S_e–1P_e transition. Furthermore, gold nanodisk arrays were designed, fabricated and integrated with the HgSe quantum-dot films. Based on the near-field resonance created by the nanodisk structure, the responsivity at the center wavelength of the HgSe quantum-dot film based narrowband photodetector can be increased. In our experiments, four narrowband photodetectors with tunable center wavelengths of 4.2 μm, 6.4 μm, 7.2 μm and 9.0 μm were fabricated. After the integration with the plasmonic nanodisk array, the responsivity at the center wavelength of the four fabricated narrowband photodetectors was enhanced by 517%@ 4.2 μm, 288%@ 6.4 μm, 257%@ 7.2 μm, and 208%@ 9.0 μm, reaching up to 145 mA W⁻¹, 92.3 mA W⁻¹, 88.6 mA W⁻¹, and 86 mA W⁻¹, respectively. The results demonstrated that the full-width at half-maxima of spectral responsivity was also decreased by 42.9% to 59.9% after the integration of the plasmonic nanodisk array. The full-width at half-maxima for four types of photodetectors were all below 2 μm (center wavelength- full-width at half-maxima: 4.2–1.05 μm, 6.4–1.15 μm, 7.2–1.25 μm, and 9.0–1.75 μm), indicating a very sharp spectral photoresponsivity.

The existence of bacteria is a great threat to food safety. Volatile compounds secreted by bacteria during their metabolic process can be dissected to evaluate bacterial contamination. Indole, as a major volatile molecule released by Escherichia coli (E. coli), was chosen to examine the presence of E. coli in this research. In this work, a graphene field-effect transistor (G-FET) was employed to detect the volatile molecule-indole based on a π-π stacking interaction between the indole and the graphene. The exposure of G-FET devices to the indole provokes a change in electrical signal, which is ascribed to the adsorption of the indole molecule onto the graphene surface via π-π stacking. The adsorption of the indole causes a charge rearrangement of the graphene-indole complex, which leads to changes in the electrical signal of G-FET biosensors with a different indole concentration. Currently, the indole biosensor can detect indole from 10 ppb to 250 ppb and reach a limit of detection of 10 ppb for indole solution detection. We believe that our detection strategy for detecting bacterial metabolic gas molecules will pave a way to developing an effective platform for bacteria detection in food safety monitoring.