Mechanical Drawing of Gas Sensors on Paper

Abstract

This communication describes a simple solvent-free method for fabricating chemoresistive gas sensors on the surface of paper. The method involves mechanical abrasion of compressed powders of sensing materials on the fibers of cellulose. We illustrate this approach by depositing conductive layers of several forms of carbon (e.g., single-walled carbon nanotubes [SWCNTs], multi-walled carbon nanotubes, and graphite) on the surface of different papers (Figure 1, Figure S1). The resulting sensors based on SWCNTs are capable of detecting NH 3 gas at concentrations as low as 0.5 part-per-million. Keywords ammonia; carbon nanotubes; mechanical abrasion; sensors; paper Detection and identification of gases and volatile organic compounds (VOCs) are critically important to human health and safety. [1-4] Gas chromatography mass spectrometry (GC-MS) is a reliable and established technology for analyzing gases and VOCs. [1] This method is highly sensitive and capable of resolving and identifying complex mixtures of analytes. The GC-MS method suffers from several limitations. The instruments are expensive, bulky, and require highly trained technicians to carry out detection and analysis. Alternative sensors for detecting gases and VOCs rely on changes in either electrical, gravimetric, or optical signals. [2, 3] These existing systems, however, involve tradeoffs in terms of cost, portability, reproducibility, requirements for calibration, sensitivity to humidity and temperature, limited shelf life, costs for training and maintenance, and ease of use by the operator. [3] Nanostructured forms of carbon, such as carbon nanotubes (CNTs), are an emerging class of materials with utility in chemical sensing. [4, 5] A useful feature of these materials is that their electrical conductance is extremely sensitive to changes in the local chemical environment. [6-8] Resistivity-based CNT sensors offer significant advantages over other methods for detecting gases and VOCs in terms of portability, ease of use, cost, and ability to operate at room temperature. [4, 5] A number of drawbacks, however, such as the dependence on expensive specialized equipment for the fabrication of devices, the need for solution processing, low solubility of CNTs in most solvents, and the limited stability of CNT-based dispersions restrict applications of these materials. Overcoming these drawbacks by developing a method for fabricating sensors from carbon-based materials that has the characteristics of being operationally simple, inexpensive, robust, and solvent-free should

From the Solution Processing of Hydrophilic Molecules to Polymer-Phthalocyanine Hybrid Materials for Ammonia Sensing in High Humidity Atmospheres

“…Both the composition of the hybrid material and the parameters of the solution processing stage can be used to tune the characteristics of the obtained materials, e.g., morphology, roughness and specific surface, hydrophilicity or hydrophobicity and eventually their optical and electronic properties. Thus, emerging sensor production technologies have become available [26–29], such as ink-jet printing, which is particularly suitable for large areas and low cost processes. Besides, electrodeposition presents clear advantages [30,31], for example when different materials need to be deposited on different electrodes located on the same substrate.…”

Pencil Drawn Strain Gauges and Chemiresistors on Paper

“…In recent years, paper-based electronics have garnered significant attention due to the potential to produce flexible, thin, low-cost, portable, and environmentally-friendly products including antennae1, touch pads2, microfluidic devices3, displays4, sound sources5, printed circuit boards6, and sensors78. Unlike traditional substrates such as silicon, glass, and/or plastic, paper fibers offer a naturally porous environment which provides an increased deposition area and allows the formation of composites using materials deposited within the cellulose fibers9.…”

A solvent-free microbial-activated air cathode battery paper platform made with pencil-traced graphite electrodes

“…Figure 4D shows representative pencil-traced hydrophilic bacteria-active areas (with four strokes) on paper according to the pencil hardness. Since the efficiency of the pencil-traced electrode is mainly decided by the physical properties of the paper-based substrate (i.e., the surface roughness)43, the material properties of the pencil lead40, and the writing force, two force conditions were evaluated: “normal” tracing (①–③, 8.34 ± 0.79 N) and “pressing-down” tracing (④ and ⑤, 15.78 ± 1.38 N). The mean RGB intensities of the 8B, 4B, HB, and 4H pencil-traced papers were 16.3, 103.3, 181.5, and 198.5, respectively.…”