A Multimodal Sensing CMOS Imager Based on Dual-Focus Imaging.

Advanced machine intelligence is empowered not only by the ever-increasing computational capability for information processing but also by sensors for collecting multimodal information from complex environments. However, simply assembling different sensors can result in bulky systems and complex data processing. Herein, it is shown that a complementary metal-oxide-semiconductor (CMOS) imager can be transformed into a compact multimodal sensing platform through dual-focus imaging. By combining lens-based and lensless imaging, visual information, chemicals, temperature, and humidity can be detected with the same chip and output as a single image. As a proof of concept, the sensor is equipped on a micro-vehicle, and multimodal environmental sensing and mapping is demonstrated. A multimodal endoscope is also developed, and simultaneous imaging and chemical profiling along a porcine digestive tract is achieved. The multimodal CMOS imager is compact, versatile, and extensible and can be widely applied in microrobots, in vivo medical apparatuses, and other microdevices.

Visual-Olfactory Synergistic Perception Based on Dual-Focus Imaging and a Bionic Learning Architecture.

The synergistic interaction of vision and olfaction is critical for both natural and artificial intelligence systems to recognize and adapt to complex environments. However, current bioinspired systems with visual and olfactory sensations are mostly assembled with separate and heterogeneous sensors, inevitably leading to bulky systems and incompatible datasets. Here, we demonstrate on-chip integration of visual and olfactory sensations through a dual-focus imaging approach. By combining lens-based visual imaging and lensless colorimetric imaging, a target object and its odor fingerprint can be captured with a single complementary metal-oxide-semiconductor imager, and the obtained multimodal images are analyzed with a bionic learning architecture for information fusion and perception. To demonstrate the capability of this system, we adapted it to food detection and achieved 100% accuracy in identifying meat freshness and category with a 10 s sampling time. In addition to the highly integrated sensor design, our approach exhibits superior accuracy and efficiency in object recognition, providing a promising approach for robotic sensing and perception.

Online Accurate Detection of Breath Acetone Using Metal Oxide Semiconductor Gas Sensor and Diffusive Gas Separation.

Breath acetone (BrAce) level is an indicator of lipid oxidation rate, which is crucial for evaluating the status of ketoacidosis, ketogenic diet, and fat burning during exercise. Despite its usefulness, detecting BrAce accurately is challenging because exhaled breath contains an enormous variety of compounds. Although many sensors and devices have been developed for BrAce measurement, most of them were tested with only synthetic or spiked breath samples, and few can detect low concentration BrAce in an online manner, which is critical for extending application areas and the wide acceptance of the technology. Here, we show that online detection of BrAce can be achieved using a metal oxide semiconductor acetone sensor. The high accuracy measurement of low concentration BrAce was enabled by separating major interference gases utilizing their large diffusion coefficients, and the accuracy is further improved by the correction of humidity effect. We anticipate that the approach can push BrAce measurement closer to being useful for various applications.

Graphene quantum dot-decorated luminescent porous silicon dressing for theranostics of diabetic wounds.

Diabetic wound healing is highly desirable but remains a great challenge owing to the continuous damage of excess reactive oxygen species (ROS) and degradation of therapeutic peptide drugs by over-expressed matrix metalloproteinase (MMP). Herein, we developed a stimuli-responsive smart dressing for theranostics of diabetic wounds using graphene quantum dots-decorated luminescent porous silicon (GQDs@PSi), which was further loaded with peptide and embedded in chitosan (CS) film. The confinement of GQDs in nanochannels of PSi endowed GQDs@PSi with efficient fluorescence resonance energy transfer (FRET) effect, leading to initial red fluorescence of PSi with complete quench of GQD's blue fluorescence. Furthermore, the decoration of GQDs on PSi surface significantly enhanced the loading capacity for peptide drugs including epidermal growth factor (EGF) and insulin (Ins) which can promote diabetic wounds healing. The peptides coloaded in GQDs@PSi exhibited sustained release behavior and could be protected in presence of MMP owing to size exclusion of PSi's nanochannels. As H2O2-triggered oxidation of PSi lead to weakened FRET effect and degradation of PSi, GQDs@PSi demonstrated H2O2-responsive ratiometric fluorescence change (from red PSi to blue GQDs) and drug release behavior. In combination with CS's degradation in the acidic and oxidation microenvironment, the smart dressing also showed stimuli-responsive drug release toward slightly acid and highly oxidative conditions in diabetic wounds. In vitro and in vivo results demonstrated the smart dressing enhanced the proliferation and migration of cells as well as significantly healed diabetic wounds. Real-time indicating of the exacerbation or healing of diabetic wounds was also realized using the rate of fluorescent discoloration of the dressing. STATEMENT OF SIGNIFICANCE: In this work, a dual luminescent nanomaterial was created by hosting graphene quantum dots (GQDs) in the nanochannel of porous silicon (PSi), which was further applied for theranostics of diabetic wound. The synergistic effect of the host-guest nanohybrid is significant. The GQDs can significantly improve the capacity for peptide drug loading and form a stimuli-response visual ratiometric sensor with luminescent PSi, which can also protect and sustain release of peptide drugs for effective diabetic wounds treatment. After embedded in a chitosan film, the smart dressing displayed H2O2-responsive visual ratiometric fluorescence change and drug release behavior. In vitro and in vivo results demonstrated the smart dressing enhanced the proliferation and migration of cells as well as significantly healed diabetic wounds.

A co-delivery platform for synergistic promotion of angiogenesis based on biodegradable, therapeutic and self-reporting luminescent porous silicon microparticles.

Insufficient angiogenesis happened in body defects such as ulceration, coronary heart disease, and chronic wounds constitutes a major challenge in tissue regeneration engineering. Owing to the poor bioactivity and maintenance of pro-angiogenic cells and factors during transplantation, new bioactive materials to tackle the barrier are highly desirable. Herein, we demonstrate a co-delivery platform for synergistic promotion of angiogenesis based on biodegradable, therapeutic, and self-reporting luminescent porous silicon (PSi) microparticles. The biodegradable and biocompatible PSi microparticles could quickly release therapeutic Si ions, which is bioactive to promote cell migration, tube formation, and angiogenic gene expression in vitro. To construct a highly efficient angiogenesis treatment platform, vascular endothelial growth factor (VEGF) was electrostatically adsorbed by PSi microparticles for effective drug loading and delivery. The dual therapeutic components (Si ions and VEGF) could release with the dissolution of Si skeleton, accompanying by the decay of photoluminescence (PL) intensity and blue shift of the maximum PL wavelength. Therefore, real-time drug release could be self-reported and assessed with the two-dimensional PL signal. The co-delivery of Si ions and VEGF displayed synergistic effect and highly efficient angiogenesis, which was evidenced by the enhancement of endothelial cell migration and tube formation in vitro with approximately 1.5-5 times higher than control. The blood vessel formation in vivo was also significantly improved as shown by the chick chorioallantoic membrane (CAM) model, in which the total length, size and junctions exhibited 2.1 ± 0.4, 4 ± 0.4, and 3.9 ± 0.3 times in comparison to control, respectively. The PSi and VEGF co-delivery system display great potential in tissue engineering as a biodegradable and self-reporting theranostic platform to promote angiogenesis.

Ratiometric Fluorescent Nanohybrid for Noninvasive and Visual Monitoring of Sweat Glucose.

Noninvasive and visual monitoring of glucose is highly desirable for diabetes diagnostics and long-term home-based health management. Owing to the correlation of the glucose level between blood and sweat, on-body sweat glucose detection provides potential for noninvasive healthcare but is highly challenging. Herein, we for the first time demonstrate a wearable skin pad based on the ratiometric fluorescent nanohybrid, which can realize noninvasive and visual monitoring of sweat glucose. Luminescent porous silicon (PSi) particles, which have a porous structure and oxidation-responsive photoluminescence decay, are chosen to load (adsorb or entrap) carbon quantum dots (CQDs) for the construction of the dual fluorescence nanohybrid. Bimetallic (Au and Ag) nanoparticles (BiM) are also co-decorated on the PSi particle to improve detection sensitivity by enhancing PSi's initial fluorescence and oxidation kinetics. Owing to the efficient fluorescence resonance energy transfer effect, BiM-CQDs@PSi initially exhibits PSi's red fluorescence with complete quenching of CQDs's blue fluorescence. The oxidation of PSi triggered by hydrogen peroxide (H2O2) weakens the FRET effect and decays PSi's fluorescence, causing ratiometric fluorescence to change from red (PSi) to blue (CQDs). A wearable skin pad is easily fabricated by co-immobilization of BiM-CQDs@PSi and glucose oxidase (GOX) in a transparent and biocompatible chitosan film supported by an adhesive polyurethane membrane. When the skin pad is attached on the body, the same ratiometric fluorescence transition (red → blue) is observed upon the stimulation of H2O2 generated in GOX-catalyzed oxidation of sweat glucose. Based on the strong correlation between the ratio of the fluorescence change and sweat glucose level, clinical tests toward diabetics and healthy volunteers can clearly indicate hyperglycemia.

Two-Dimensional Electrochemiluminescence on Porous Silicon Platform for Explosive Detection and Discrimination.

This work established a rapid and sensitive explosive detection and recognition technique. We report a two-dimensional electrochemiluminescence (2-D ECL) method based on porous silicon (pSi) by monitoring the dynamic change in peak position and peak intensity of pSi-ECL. Gold nanoparticles (AuNPs) were deposited on the pSi surface to promote the electrochemical reaction and electron transfer efficiency at the pSi-electrolyte interface. The 2-D ECL can effectively detect and discriminate different classes of explosives including nitro compounds, peroxides with nitrogen atoms, and peroxides without nitrogen atoms due to their different oxidation and electron transfer ability.