Abstract The accurate, continuous analysis of healthcare-relevant gases such as nitrogen oxides (NO x ) in a humid environment remains elusive for low-cost, stretchable gas sensing devices. This study presents the design and demonstration of a moisture-resistant, stretchable NO x gas sensor based on laser-induced graphene (LIG). Sandwiched between a soft elastomeric substrate and a moisture-resistant semipermeable encapsulant, the LIG sensing and electrode layer is first optimized by tuning laser processing parameters such as power, image density, and defocus distance. The gas sensor, using a needlelike LIG prepared with optimal laser processing parameters, exhibits a large response of 4.18‰ ppm −1 to NO and 6.66‰ ppm −1 to NO 2 , an ultralow detection limit of 8.3 ppb to NO and 4.0 ppb to NO 2 , fast response/recovery, and excellent selectivity. The design of a stretchable serpentine structure in the LIG electrode and strain isolation from the stiff island allows the gas sensor to be stretched by 30%. Combined with a moisture-resistant property against a relative humidity of 90%, the reported gas sensor has further been demonstrated to monitor the personal local environment during different times of the day and analyze human breath samples to classify patients with respiratory diseases from healthy volunteers. Moisture-resistant, stretchable NO x gas sensors can expand the capability of wearable devices to detect biomarkers from humans and exposed environments for early disease diagnostics.
more »
« less
Vanadium Oxide‐Doped Laser‐Induced Graphene Multi‐Parameter Sensor to Decouple Soil Nitrogen Loss and Temperature
Abstract Monitoring nitrogen utilization efficiency and soil temperature in agricultural systems for timely intervention is essential for crop health with reduced environmental pollution. Herein, this work presents a high‐performance multi‐parameter sensor based on vanadium oxide (VOX)‐doped laser‐induced graphene (LIG) foam to completely decouple nitrogen oxides (NOX) and temperature. The highly porous 3D VOX‐doped LIG foam composite is readily obtained by laser scribing vanadium sulfide (V5S8)‐doped block copolymer and phenolic resin self‐assembled films. The heterojunction formed at the LIG/VOXinterface provides the sensor with enhanced response to NOXand an ultralow limit of detection of 3 ppb (theoretical estimate of 451 ppt) at room temperature. The sensor also exhibits a wide detection range, fast response/recovery, good selectivity, and stability over 16 days. Meanwhile, the sensor can accurately detect temperature over a wide linear range of 10–110 °C. The encapsulation of the sensor with a soft membrane further allows for temperature sensing without being affected by NOX. The unencapsulated sensor operated at elevated temperature removes the influences of relative humidity and temperature variations for accurate NOXmeasurements. The capability to decouple nitrogen loss and soil temperature paves the way for the development of future multimodal decoupled electronics for precision agriculture and health monitoring.
more »
« less
- Award ID(s):
- 1933072
- PAR ID:
- 10418784
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Materials
- Volume:
- 35
- Issue:
- 14
- ISSN:
- 0935-9648
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract We use TROPOMI (TROPOspheric Monitoring Instrument) tropospheric nitrogen dioxide (NO2) measurements to identify cropland soil nitrogen oxide (NOx = NO + NO2) emissions at daily to seasonal scales in the U.S. Southern Mississippi River Valley. Evaluating 1.5 years of TROPOMI observations with a box model, we observe seasonality in local NOxenhancements and estimate maximum cropland soil NOxemissions (15–34 ng N m−2 s−1) early in growing season (May–June). We observe soil NOxpulsing in response to daily decreases in volumetric soil moisture (VSM) as measured by the Soil Moisture Active Passive (SMAP) satellite. Daily NO2enhancements reach up to 0.8 × 1015 molecules cm−24–8 days after precipitation when VSM decreases to ~30%, reflecting emissions behavior distinct from previously defined soil NOxpulse events. This demonstrates that TROPOMI NO2observations, combined with observations of underlying process controls (e.g., soil moisture), can constrain soil NOxprocesses from space.more » « less
-
This study aimed to explore lignin as a naturally occurring aromatic precursor for the synthesis of LIG and further fabrication of ultrasensitive strain sensors for the detection of small deformations. One-step direct laser writing (DLW) induced high quality porous graphene, so called laser induced graphene (LIG), from kraft lignin under the conditions optimized for laser power, focus distance, and lignin loading. An electrode based on the resulting LIG was facilely fabricated by transferring LIG onto an elastomeric substrate ( i.e. , Dragon Skin™). The novel LIG transfer was facilitated by spin coating followed by water lifting, leading to the full retention of porous graphene onto the elastomeric substrate. The strain sensor was shown to be highly sensitive to small human body motions and tiny deformations caused by vibrations. It had a working range of up to 14% strain with a gauge factor of 960 and showed high stability as evidenced by repetitive signals over 10 000 cycles at 4% strain. The sensor was also successfully demonstrated for detecting human speaking, breath, seismocardiography (SCG), and movement of pulse and eye. Overall, the lignin-derived LIG can serve as excellent piezoresistive materials for wearable, stretchable, and ultrasensitive strain sensors with applications in human body motion monitoring and sound-related applications.more » « less
-
Abstract Straining the vanadium dimers along the rutilec‐axis can be used to tune the metal‐to‐insulator transition (MIT) of VO2but has thus far been limited to TiO2substrates. In this work VO2/MgF2epitaxial films are grown via molecular beam epitaxy (MBE) to strain engineer the transition temperature (TMIT). First, growth parameters are optimized by varying the synthesis temperature of the MgF2(001) substrate (TS) using a combination of X‐ray diffraction techniques, temperature dependent transport, and soft X‐ray photoelectron spectroscopy. It is determined thatTSvalues greater than 350 °C induce Mg and F interdiffusion and ultimately the relaxation of the VO2layer. Using the optimized growth temperature, VO2/MgF2(101) and (110) films are then synthesized. The three film orientations display MITs with transition temperatures in the range of 15–60 °C through precise strain engineering.more » « less
-
Abstract Vanadium dioxide (VO2) is a well‐studied Mott‐insulator because of the very abrupt physical property switching during its semiconductor‐to‐metal transition (SMT) around 341 K (68 °C). In this work, through novel oxide‐metal nanocomposite designs (i.e., Au:VO2and Pt:VO2), a very broad range of SMT temperature tuning from≈323.5 to≈366.7 K has been achieved by varying the metallic secondary phase in the nanocomposites (i.e., Au:VO2and Pt:VO2thin films, respectively). More surprisingly, the SMTTccan be further lowered to≈301.8 K (near room temperature) by reducing the Au particle size from 11.7 to 1.7 nm. All the VO2nanocomposite thin films maintain superior phase transition performance, i.e., large transition amplitude, very sharp transition, and narrow width of thermal hysteresis. Correspondingly, a twofold variation of the complex dielectric function has been demonstrated in these metal‐VO2nanocomposites. The wide range physical property tuning is attributed to the band structure reconstruction at the metal‐VO2phase boundaries. This demonstration paved a novel approach for tuning the phase transition property of Mott‐insulating materials to near room temperature transition, which is important for sensors, electrical switches, smart windows, and actuators.more » « less
An official website of the United States government
