Figure 1.
SEM image of a differential pair of COMB micro-capacitor.
Figure 1.
SEM image of a differential pair of COMB micro-capacitor.
Figure 2.
Chemical structures of the silanes used in this work.
Figure 2.
Chemical structures of the silanes used in this work.
Figure 3.
Modification of SiO2 surface with APTMS molecules: (a) SiO2 surface, (b) modified SiO2 surface (c) interaction of analyte with the modified surface.
Figure 3.
Modification of SiO2 surface with APTMS molecules: (a) SiO2 surface, (b) modified SiO2 surface (c) interaction of analyte with the modified surface.
Figure 4.
(a) High-energy resolution N1s XPS spectra from UPS, (b) from APTMS modified sensor surface, (c) High-energy resolution C 1s XPS spectra from UPS and (d) from APTMS modified sensor surface.
Figure 4.
(a) High-energy resolution N1s XPS spectra from UPS, (b) from APTMS modified sensor surface, (c) High-energy resolution C 1s XPS spectra from UPS and (d) from APTMS modified sensor surface.
Figure 5.
Block diagram which shows 16 SiPs (on the left), each composed of two differently modified sensors (up to 4 possible) and one low noise ASIC. The last SiP contains temperature and pressure sensor and associated signal processing electronics. The DSP is currently implemented on the FPGA together with control logic, and USB/Bluetooth interface. The power management unit deliver appropriate supply voltages for the blocks, while the PC controls the measurement system and gas generator, as well as takes care of additional signal processing, averaging and storage.
Figure 5.
Block diagram which shows 16 SiPs (on the left), each composed of two differently modified sensors (up to 4 possible) and one low noise ASIC. The last SiP contains temperature and pressure sensor and associated signal processing electronics. The DSP is currently implemented on the FPGA together with control logic, and USB/Bluetooth interface. The power management unit deliver appropriate supply voltages for the blocks, while the PC controls the measurement system and gas generator, as well as takes care of additional signal processing, averaging and storage.
Figure 6.
Sixteen-channel vapour trace detection system: (a) Implemented detection system without gas generator, where inlets A and B are connected to the gas generator. (b) Ceramic gas distribution system and SiP holder, (c) One differential sensor, (d) SiP composed of one ASIC and two differential sensors, (e) layout of the ASIC that implements one channel lock-in amplifier that is capable to process the signals from 4 differential sensors.
Figure 6.
Sixteen-channel vapour trace detection system: (a) Implemented detection system without gas generator, where inlets A and B are connected to the gas generator. (b) Ceramic gas distribution system and SiP holder, (c) One differential sensor, (d) SiP composed of one ASIC and two differential sensors, (e) layout of the ASIC that implements one channel lock-in amplifier that is capable to process the signals from 4 differential sensors.
Figure 7.
Control screen on the PC, through which it is possible to set the important parameters of the sensors interface, AFE (ASIC) and DSP. A signal from one sensor is presented as a function of time in the lower-right part of the command screen. The responses of all active sensors are presented in real time on the green pixels of the sensor array in the lower left part of the screen. Pixels are differently coloured depending on the real-time value of the signal.
Figure 7.
Control screen on the PC, through which it is possible to set the important parameters of the sensors interface, AFE (ASIC) and DSP. A signal from one sensor is presented as a function of time in the lower-right part of the command screen. The responses of all active sensors are presented in real time on the green pixels of the sensor array in the lower left part of the screen. Pixels are differently coloured depending on the real-time value of the signal.
Figure 8.
Block diagram of one channel of the detection system. It is composed of the blue region with maximum of 4 differential sensors (different colour represent different modification), the ASIC in yellow region which contains analogue signal processing electronics together with calibration DACs (in white regions), and on the right, in the grey area, the DSP part of the signal processing electronics of one channel.
Figure 8.
Block diagram of one channel of the detection system. It is composed of the blue region with maximum of 4 differential sensors (different colour represent different modification), the ASIC in yellow region which contains analogue signal processing electronics together with calibration DACs (in white regions), and on the right, in the grey area, the DSP part of the signal processing electronics of one channel.
Figure 9.
Simulated spectrum at the output of the ASIC with four differential sensors connected to one measurement channel, where each sensor is connected to excitation signal with 5 V amplitude and different frequencies. The amplitudes of spectral components correspond to different capacitance differences; for example the 4th sensor has capacitance difference of 5 aF which corresponds to the smallest spectral line (S4: dC4 at frequency 16 kHz) with SnR of 44 dB, which leads to possible detection sensitivity of 44 zF/.
Figure 9.
Simulated spectrum at the output of the ASIC with four differential sensors connected to one measurement channel, where each sensor is connected to excitation signal with 5 V amplitude and different frequencies. The amplitudes of spectral components correspond to different capacitance differences; for example the 4th sensor has capacitance difference of 5 aF which corresponds to the smallest spectral line (S4: dC4 at frequency 16 kHz) with SnR of 44 dB, which leads to possible detection sensitivity of 44 zF/.
Figure 10.
Simplified circuit diagram of one-half of the charge amplifier that includes two differential sensors. Most important parasitic capacitors are marked on that picture together with most important noise sources.
Figure 10.
Simplified circuit diagram of one-half of the charge amplifier that includes two differential sensors. Most important parasitic capacitors are marked on that picture together with most important noise sources.
Figure 11.
(a) Schematic diagram of the vapour generator used for TNT, RDX, DNT and H2O measurements. N2 gasfrom a storage tank is thermally stabilized (T) and divided into three parallel flow lines (Φ1, Φ2, Φ3), each with electronic flow regulator (F1, F2, F3). The switching between the pure carrier gas and gas with the known concentration of the explosive’s vapour, while keeping the total mass flow constant, is done by mixing the gas from an empty glass cylinder (Φ1) with either pure gas (Φ2) or with saturated gas (Φ3). Three valves V1, V2 and V3 control the mixing. (b) A model of the actual vapour generator used in the experiments. Red, blue, and green colours represent individual flow lines.
Figure 11.
(a) Schematic diagram of the vapour generator used for TNT, RDX, DNT and H2O measurements. N2 gasfrom a storage tank is thermally stabilized (T) and divided into three parallel flow lines (Φ1, Φ2, Φ3), each with electronic flow regulator (F1, F2, F3). The switching between the pure carrier gas and gas with the known concentration of the explosive’s vapour, while keeping the total mass flow constant, is done by mixing the gas from an empty glass cylinder (Φ1) with either pure gas (Φ2) or with saturated gas (Φ3). Three valves V1, V2 and V3 control the mixing. (b) A model of the actual vapour generator used in the experiments. Red, blue, and green colours represent individual flow lines.
Figure 12.
(a) The measurement set-up for measuring the response to different solvents in ambient air of the laboratory. (b) The set-up for measuring e-nose response to toxic gases in a fume cupboard.
Figure 12.
(a) The measurement set-up for measuring the response to different solvents in ambient air of the laboratory. (b) The set-up for measuring e-nose response to toxic gases in a fume cupboard.
Figure 13.
(a) Response of UPS sensor to switching between pure nitrogen and nitrogen with the maximal concentration of TNT vapour. The red lines indicate measurements that were averaged to determine the amplitude of response. (b) Response of DMS sensor to switching between pure nitrogen and nitrogen with the maximal concentration of TNT vapour.
Figure 13.
(a) Response of UPS sensor to switching between pure nitrogen and nitrogen with the maximal concentration of TNT vapour. The red lines indicate measurements that were averaged to determine the amplitude of response. (b) Response of DMS sensor to switching between pure nitrogen and nitrogen with the maximal concentration of TNT vapour.
Figure 14.
(a) Time response of the sensor functionalized with APhs to the TNT vapour at ½ vapour pressure of the TNT. (b) Time response of the sensor functionalized with UPS to H2O vapour at approx. vapour pressure. In both cases the response is without dimensions and corresponds to
Figure 14.
(a) Time response of the sensor functionalized with APhs to the TNT vapour at ½ vapour pressure of the TNT. (b) Time response of the sensor functionalized with UPS to H2O vapour at approx. vapour pressure. In both cases the response is without dimensions and corresponds to
Figure 15.
Responses of differently functionalized sensors to vapours of different molecules: TNT, RDX, DNT, H2O and propane. The responses were normalized to the response of sensor UPS1A. The positions in the array and different colours of individual pixels shows differently functionalised sensors. The type of the functionalisation layer is printed in the array at the lower right corner (upper case names, for example DMS1, correspond to the active sensor while the lower case names, such as ups1a, correspond to reference sensors, where functionalized layer is removed on both parts of differential sensor).
Figure 15.
Responses of differently functionalized sensors to vapours of different molecules: TNT, RDX, DNT, H2O and propane. The responses were normalized to the response of sensor UPS1A. The positions in the array and different colours of individual pixels shows differently functionalised sensors. The type of the functionalisation layer is printed in the array at the lower right corner (upper case names, for example DMS1, correspond to the active sensor while the lower case names, such as ups1a, correspond to reference sensors, where functionalized layer is removed on both parts of differential sensor).
Figure 16.
Responses of differently functionalized sensors to vapours of different molecules: FeS, NH3, methane, methanol, and acetone. The electronic response of a given sensor was normalized to the response of the sensor UPS1A. The position in the array and the colours of individual pixels shows differently functionalised sensors. The type of the functionalisation layer is printed in the array at the lower right corner (upper case names, for example DMS1, correspond to the active sensor while the lower-case names correspond to reference sensors, where functionalized layer is removed on both parts of differential sensor).
Figure 16.
Responses of differently functionalized sensors to vapours of different molecules: FeS, NH3, methane, methanol, and acetone. The electronic response of a given sensor was normalized to the response of the sensor UPS1A. The position in the array and the colours of individual pixels shows differently functionalised sensors. The type of the functionalisation layer is printed in the array at the lower right corner (upper case names, for example DMS1, correspond to the active sensor while the lower-case names correspond to reference sensors, where functionalized layer is removed on both parts of differential sensor).
Figure 17.
Responses of differently functionalized sensors to vapours of different molecules: H2S, NCH, ethanol, and toluene. The electronic response of a given sensor was normalized to the response of the sensor UPS1A. The position in the array and the colours of individual pixels shows differently functionalised sensors. The type of the functionalisation layer is printed in the array at the lower right corner (upper case names, for example DMS1, correspond to the active sensor while the lower case names correspond to reference sensors, where functionalized layer is removed on both parts of differential sensor).
Figure 17.
Responses of differently functionalized sensors to vapours of different molecules: H2S, NCH, ethanol, and toluene. The electronic response of a given sensor was normalized to the response of the sensor UPS1A. The position in the array and the colours of individual pixels shows differently functionalised sensors. The type of the functionalisation layer is printed in the array at the lower right corner (upper case names, for example DMS1, correspond to the active sensor while the lower case names correspond to reference sensors, where functionalized layer is removed on both parts of differential sensor).
Figure 18.
The complete matrix of absolute values of responses of differently functionalized sensors to different vapour traces. Each row on y-axis corresponds to modification layer; the bars are presented in different colour, so each colour presents one modification layer, while each column on x-axis corresponds to different vapour of the experiment. The height of each pixel represents relative response of particular sensor to the particular target molecule in the carrier gas. Sensors with lower case letters (i.e., ups1a) are the reference sensors where the modification layer is removed completely by laser treatment.
Figure 18.
The complete matrix of absolute values of responses of differently functionalized sensors to different vapour traces. Each row on y-axis corresponds to modification layer; the bars are presented in different colour, so each colour presents one modification layer, while each column on x-axis corresponds to different vapour of the experiment. The height of each pixel represents relative response of particular sensor to the particular target molecule in the carrier gas. Sensors with lower case letters (i.e., ups1a) are the reference sensors where the modification layer is removed completely by laser treatment.
Figure 19.
Scaled responses of differently modified sensors to H2O, TNT and DNT molecules at vapour pressure. Scaled response to H2O molecules is attenuated by factor greater than more than 105 (100 dB) in the worst case.
Figure 19.
Scaled responses of differently modified sensors to H2O, TNT and DNT molecules at vapour pressure. Scaled response to H2O molecules is attenuated by factor greater than more than 105 (100 dB) in the worst case.
Figure 20.
Comparison of the response of the EDA sensor to TNT in the presence of different water vapour background concentration of 36% and 28% respectively.
Figure 20.
Comparison of the response of the EDA sensor to TNT in the presence of different water vapour background concentration of 36% and 28% respectively.
Table 1.
Surface composition (in atomic %) of SiO2 sensors before and after silanization with different silanes (6 h of deposition at 25 °C in acetonitrile).
Table 1.
Surface composition (in atomic %) of SiO2 sensors before and after silanization with different silanes (6 h of deposition at 25 °C in acetonitrile).
Sample | C (at. %) | O (at. %) | Si (at. %) | N (at. %) |
---|
Reference (blank) sensor | 9.9 | 47.3 | 42.8 | |
APTMS | 34.9 | 34.5 | 25.1 | 5.5 |
APhS | 33.6 | 33.4 | 29.6 | 3.4 |
UPS | 20.8 | 42.8 | 31.8 | 4.6 |
EDA | 21.6 | 43.7 | 32 | 2.7 |
DMS | 12.1 | 48.5 | 38 | 1.4 |
ODS | 17.5 | 42.3 | 40.2 | |
Table 2.
Density of molecules for different vapours together with responses and scaled responses of APhS sensor.
Table 2.
Density of molecules for different vapours together with responses and scaled responses of APhS sensor.
Vapour | H2O | TNT | DNT |
---|
Density Ns(x)/N(N2) | 10−2 | 10−9 | 10−6 |
Response ΔR | 1.2 × 10+3 | 4 × 10+3 | 1.7 × 10+3 |
Scaled response Dscaled | 1.2 × 10+5 | 4 × 10+12 | 1.7 × 10+9 |
Scaled response relative to H2O | 1 | 3.3 × 10+7 | 1.4 × 10+4 |