The present inventive concept relates to a battery-free gas sensor or humidity sensor comprising a metal-organic framework and a method of manufacturing the same. In a photodiode-type battery-free gas sensor or humidity sensor according to the present inventive concept, since photoelectron collection electrodes are formed at certain intervals between P-N junction layers, when gas is adsorbed thereon, the gas can be detected without an extra power source by change of photocurrent. Due to fine pores of the metal-organic framework, gas sensitivity may be increased and stability of catalysts may be improved. When catalysts are not provided, humidity may be detected. Therefore, a system that used the photodiode-type battery-free gas sensor and the photodiode-type battery-free humidity sensor together may be performed humidity correction to accurately measure an amount of a gas.

According to improvement of the receptor layer of various sensors of the type for detecting physical parameters (for example, a surface stress sensor, QCM, and SPR), all of high sensitivity, selectivity, and durability are achieved simultaneously. A porous material or a particulate material, e.g., nanoparticles, is used in place of a uniform membrane which has been conventionally used as a receptor layer. Accordingly, the sensitivity can be controlled by changing the membrane thickness of the receptor layer, the selectivity can be controlled by changing a surface modifying group to be fixed on the porous material or particulate material, and the durability can be controlled by changing the composition and surface properties of the porous material or particulate material.

Disclosed herein is a chemical sensing system, comprising: a sensor configured to adsorb an analyte; an electronic circuit to operate the sensor; and a microcontroller in communication with the sensor and the electronic circuit. The microcontroller can also be configured to provide a real-time signal indicative of a concentration of the analyte. The sensor can comprise a microelectromechanical system (MEMS) resonator and a sensing film configured to adsorb the analyte, the sensing film coating at least a portion of the sensor. The MEMS resonator can comprise a second sensor, such as an impedimetric sensor to measure at least a second property of the sensing film. The electronic circuit can process signals stemming from at least two properties of the same sensing film, such as the changes in mass and dielectric constant of the same sensing film due to adsorption of analyte.

For sensing pH of a fluid, a heating apparatus of a semiconductor die controls a temperature of the fluid to a first temperature. A first voltage of a gate of a floating gate transistor of the semiconductor die is measured while the temperature of the fluid is at the first temperature. Also, the heating apparatus controls the temperature of the fluid to a second temperature that is different than the first temperature. A second voltage of the gate is measured while the temperature of the fluid is at the second temperature. The pH of the fluid is determined based on the first and second voltages, the first temperature and the second temperature.

An electrical device includes at least one graphene quantum capacitance varactor. In some examples, the graphene quantum capacitance varactor includes an insulator layer, a graphene layer disposed on the insulator layer, a dielectric layer disposed on the graphene layer, a gate electrode formed on the dielectric layer, and at least one contact electrode disposed on the graphene layer and making electrical contact with the graphene layer. In other examples, the graphene quantum capacitance varactor includes an insulator layer, a gate electrode recessed in the insulator layer, a dielectric layer formed on the gate electrode, a graphene layer formed on the dielectric layer, wherein the graphene layer comprises an exposed surface opposite the dielectric layer, and at least one contact electrode formed on the graphene layer and making electrical contact with the graphene layer.

An impedance measurement system for detecting an analyte in a sample is disclosed. The system includes first, second, and third electrodes, wherein at least a portion of the third electrode is positioned between the first and second electrodes, means for generating an electromagnetic field between the first and second electrodes, means for electrically controlling the third electrode, wherein the third electrode modifies the electromagnetic field, and a processor for detecting a presence of the analyte in the sample, based at least in part on a property of the electromagnetic field.

A substrate that includes a base layer having a first principal surface defining a plurality of first trenches and intervening first lands, and a cover layer provided over the first principal surface of the base layer and covering the first trenches and first lands substantially conformally, wherein the surface of the cover layer remote from the first principal surface of the base layer comprises a plurality of second trenches and intervening second lands defined at a smaller scale than the first trenches and first lands. The substrate may be used to fabricate a capacitive element in which thin film layers are provided and conformally cover the second trenches and second lands of the cover layer, to create a metal-insulator-metal structure having high capacitance density.

An electrostatically controlled sensor includes a GaN/AlGaN heterostructure having a 2DEG channel in the GaN layer. Source and drain contacts are electrically coupled to the 2DEG channel through the AlGaN layer. A gate dielectric is formed over the AlGaN layer, and gate electrodes are formed over the gate dielectric, wherein each gate electrode extends substantially entirely between the source and drain contacts, wherein the gate electrodes are separated by one or more gaps (which also extend substantially entirely between the source and drain contacts). Each of the one or more gaps defines a corresponding sensing area between the gate electrodes for receiving an external influence. A bias voltage is applied to the gate electrodes, such that regions of the 2DEG channel below the gate electrodes are completely depleted, and regions of the 2DEG channel below the one or more gaps in the direction from source to drain are partially depleted.

The present disclosure provides a fluid sensor and a method for fabricating a fluid sensor. The fluid sensor includes a substrate including a first material and having a first surface and a second surface opposite to the first surface, wherein the substrate further comprises a recess recessed from the first surface, a first conductive layer over the first surface of the substrate, a protection layer between the first surface of the substrate and the first conductive layer, wherein the protection layer includes a second material, and a through via connected to the recess.

Detection and capture of toxic nitrogen oxides (NO.sub.x) is important for emissions control of exhaust gases and general public health. The low power sensor provides direct electrically detection of trace (0.5-5 ppm) NO.sub.2 at relatively low temperatures (50° C.) via changes in the electrical properties of nitrogen-oxide-capture active materials. For example, the high impedance of MOF-74 enables applications requiring a near-zero power sensor or dosimeter, such as for smart industrial systems and the internet of things, with 0.8 mg MOF-74 active material drawing <15 pW for a macroscale sensor 35 mm.sup.2 area.