Self-sensing array of microcantilevers for chemical detection

Abstract

The invention provides a chemical detection system for detecting at least one target chemical species, including a self-sensed cantilevered probe array having a plurality of self-sensed cantilevered probes, at least one chemical-sensitive coating material applied to at least one cantilevered probe in the cantilevered probe array, and an interface circuit that is coupled to the cantilevered probe array. At least one cantilevered probe in the cantilevered probe array exhibits a shifted cantilevered probe response when the cantilevered probe array is exposed to the target chemical species and the interface circuit actuates the cantilevered probe. A handheld chemical detection system and a method of operation are also disclosed.

1 - 32 . (canceled)  
     
     
         33 . The method of  claim 69  wherein at least a portion of the cantilevered probes in the cantilevered probe array is frequency-differentiated.  
     
     
         34 . The method of  claim 69  wherein the target chemical species detected is mercury, hydrogen, an alcohol, water vapor, an explosive material, a chemical element, a chemical compound, an organic material, an inorganic material, a gaseous substance, a liquid, a biological material, a DNA strand, a bioactive agent, a toxin, or combinations thereof.  
     
     
         35 . The method of  claim 69  wherein exposing a self-sensed cantilevered probe array to a target chemical species comprises exposing the cantilevered probe array to a liquid or a gas.  
     
     
         36 . The method of  claim 69 , further comprising actuating the exposed cantilevered probe array by applying an excitation voltage to a piezoelectric material disposed on each cantilevered probe in the cantilevered probe array.  
     
     
         37 . The method of  claim 69  wherein the cantilevered probe array comprises at least two series-connected cantilevered probes electrically connected to a pair of cantilevered probe array drive pads.  
     
     
         38 . The method of  claim 69  wherein the cantilevered probe array comprises at least two parallel-connected cantilevered probes electrically connected to a pair of cantilevered probe array drive pads.  
     
     
         39 . The method of  claim 69  wherein the cantilevered probe array comprises a network of series-connected and parallel-connected cantilevered probes electrically connected to a pair of cantilevered probe array drive pads.  
     
     
         40 . The method of  claim 69 , further comprising actuating the exposed cantilevered probe array by scanning the cantilevered probes through a predetermined frequency range.  
     
     
         41 . The method of  claim 69 , further comprising actuating the exposed cantilevered probe array by driving the exposed array at a resonant frequency of the at least one cantilevered probe in the cantilevered probe array.  
     
     
         42 . The method of  claim 69 , further comprising actuating the exposed cantilevered probe array by driving the exposed array at a predetermined frequency, wherein the predetermined frequency is off-resonance with respect to at least one cantilevered probe in the cantilevered probe array.  
     
     
         43 . The method of  claim 69  further comprising actuating the exposed cantilevered probe array by applying an electrical impulse to the cantilevered probe array.  
     
     
         44 . The method of  claim 69  wherein detecting the cantilevered probe response from the at least one actuated cantilevered probe comprises measuring one of a shifted resonant frequency, a shifted Q factor, a shifted impedance, and a shifted deflection amplitude.  
     
     
         45 . The method of  claim 69  wherein detecting the cantilevered probe response from the at least one actuated cantilevered probe comprises performing a fast Fourier transform on the cantilevered probe response.  
     
     
         46 . The method of  claim 69  wherein determining the target chemical species based on the cantilevered probe response comprises comparing a measured shift from the at least one actuated cantilevered probe to a reference set of cantilevered probe responses, and determining the target chemical species based on the reference set of cantilevered probe responses.  
     
     
         47 . The method of  claim 46  wherein the reference set of cantilevered probe responses comprises a learned set.  
     
     
         48 . The method of  claim 69  further comprising: 
 detecting a reference cantilevered probe response from at least one reference cantilevered probe in the cantilevered probe array; and    determining the target chemical species based on a reference cantilevered probe response.    
     
     
         49 . The method of  claim 69  further comprising applying a chemical-sensitive coating material to the at least one cantilevered probe in the cantilevered probe array.  
     
     
         50 . The method of  claim 49  wherein the chemical-sensitive coating material is an epoxy resin, a fluoropolymer, a gold layer, a palladium layer, an alcohol-absorbent polymer, a water-absorbent material, a chemical-sensitive polymer, a chemical-sensitive layer, a biosensitive material, a thiol, or combinations thereof.  
     
     
         51 . The method of  claim 49  wherein applying the coating material comprises one of dipping, spraying, or dispensing a coating material onto a portion of the at least one cantilevered probe.  
     
     
         52 . The method of  claim 49  wherein applying the coating material comprises masking the at least one cantilevered probe and applying the chemical-sensitive coating through the mask.  
     
     
         53 . The method of  claim 69  wherein applying the coating material comprises spraying a non-homogeneous coating material onto a set of cantilevered probes in the cantilevered probe array.  
     
     
         54 . The method of  claim 69  further comprising applying a plurality of chemical-sensitive coating materials to a set of cantilevered probes in the cantilevered probe array.  
     
     
         55 . The method of  claim 69  further comprising heating the resistive heater coupled to the at least one cantilevered probe to initialize the cantilevered probe prior to exposing the cantilevered probe array to the target chemical species.  
     
     
         56 . The method of  claim 69  further comprising heating the resistive heater coupled to the at least one cantilevered probe to react the target chemical species.  
     
     
         57 . The method of  claim 69  further comprising applying a species attraction potential to a species attraction electrode disposed on the at least one cantilevered probe in the cantilevered probe array.  
     
     
         58 . The method of  claim 69  further comprising transporting the target chemical species to the cantilevered probe array.  
     
     
         59 . The method of  claim 69  further comprising concentrating the target chemical species proximal to the cantilevered probe array.  
     
     
         60 - 68 . (canceled)  
     
     
         69 . A method of chemical detection, comprising: 
 exposing a self-sensed cantilevered probe array to a target chemical species, thereby providing an exposed cantilevered probe array; heating a resistive heater coupled to at least one cantilevered probe to analyze the target chemical species;    actuating the exposed cantilevered probe array;    detecting a cantilevered probe response from the at least one self-sensed cantilevered probe in the cantilevered probe array; and    determining the target chemical species based on the cantilevered probe response.    
     
     
         70 . The method of  claim 69  further comprising heating the resistive heater coupled to the at least one cantilevered probe to initialize the cantilevered probe prior to exposing the cantilevered probe array to the target chemical species.  
     
     
         71 - 80 . (canceled)  
     
     
         81 . The method of  claim 69  wherein at least one of the plurality of cantilevered probes is at least partially made from one or more materials comprising a polymeric layer.  
     
     
         82 . The method of  claim 69 , wherein at least one of the plurality of cantilevered probes is at least partially made from one or more materials comprising a piezoelectric material.  
     
     
         83 - 84 . (canceled)  
     
     
         85 . The method of  claim 69 , wherein at least one of the plurality of cantilevered probes is at least partially made from one or more materials comprising a piezoelectric material, silicon, polysilicon, silicon nitride, a metal, a metal alloy, a metal sheet, a metal film, a ceramic material, an ionic compound, a zinc oxide film, a PZT film, a polymeric layer, or combinations thereof.  
     
     
         86 . The method of  claim 69 , wherein the chemical-sensitive coating material comprises an epoxy resin, a fluoropolymer, a gold layer, a palladium layer, an alcohol-absorbent polymer, a water-absorbent material, a chemical-sensitive polymer, a chemical-sensitive layer, a biosensitive material, a thiol, or combinations thereof.  
     
     
         87 . The method of  claim 82 , wherein the chemical-sensitive coating material comprises an epoxy resin, a fluoropolymer, a gold layer, a palladium layer, an alcohol-absorbent polymer, a water-absorbent material, a chemical-sensitive polymer, a chemical-sensitive layer, a biosensitive material, a thiol, or combinations thereof.  
     
     
         88 - 96 . (canceled)  
     
     
         97 . A cantilevered probe array system for detecting at least one target chemical species, comprising: 
 a cantilevered probe array comprising a plurality of cantilevered probes, each of the plurality of cantilevered probes comprising: 
 a piezoelectric layer;  
 a first electrode in electrical communication with the piezoelectric layer;  
 a second electrode in electrical communication with the piezoelectric layer;  
 a resistive heater;  
   a first electrical lead; and    a second electrical lead;    wherein the first and second leads are in electrical communication with the piezoelectric layer of each of the plurality of cantilevered probes.    
     
     
         98 . The cantilevered probe array system of  claim 97 , further comprising a circuit coupled to the cantilevered probe array, including the piezoelectric layers of at least a portion of the plurality of cantilevered probes, the circuit comprising an excitation voltage generator in electrical communication with the piezoelectric layers of each of the cantilevered probes of the at least a portion of the plurality of cantilevered probes, and a signal detector in electrical communication with the piezoelectric layers of each of the cantilevered probes of the at least a portion of the plurality of cantilevered probes; wherein at least one cantilevered probe in the cantilevered probe array exhibits a shifted signal that is detected by the signal detector when the cantilevered probe array is exposed to the target chemical species and the at least one cantilevered probe is moved by the circuit.  
     
     
         99 . The cantilevered probe array system of  claim 98  wherein the excitation voltage generator comprises an oscillator circuit operating at a predetermined frequency, wherein the predetermined frequency is off-resonance with respect to at least one cantilevered probe in the cantilevered probe array.  
     
     
         100 . The cantilevered probe array system of  claim 98  wherein the excitation voltage generator comprises an impulse circuit for applying an electrical impulse to the cantilevered probe array.  
     
     
         101 . The cantilevered probe array system of  claim 98  wherein the signal detector includes a fast Fourier transform generator to perform a fast Fourier transform on the shifted signal.  
     
     
         102 . The cantilevered probe array system of  claim 98  wherein the circuit detects a shifted signal from at least one actuated cantilevered probe.  
     
     
         103 . The cantilevered probe array system of  claim 102  wherein the shifted signal comprises one of a shifted resonant frequency, a shifted Q factor, a shifted impedance, and a shifted deflection amplitude.  
     
     
         104 . The cantilevered probe array system of  claim 98  further comprising a controller in communication with the circuit; wherein the controller receives a shifted signal from a set of cantilevered probes in the cantilevered probe array, and wherein the target chemical species is determined based on the shifted signal.  
     
     
         105 . The cantilevered probe array system of  claim 104 , wherein the controller comprises an analyzer.  
     
     
         106 . The cantilevered probe array system of  claim 98  further comprising a controller in communication with the circuit; wherein the controller receives a shifted signal from a set of cantilevered probes in the cantilevered probe array, and wherein the target chemical species is determined based on a comparison between the shifted signal and a reference set of cantilevered probe signals.  
     
     
         107 . The cantilevered probe array system of  claim 106  wherein the reference set of cantilevered probe signals comprises a learned set.  
     
     
         108 . The cantilevered probe array system of  claim 98  wherein the target chemical species detected is mercury, hydrogen, an alcohol, water vapor, an explosive material, a chemical element, a chemical compound, an organic material, an inorganic material, a gaseous substance, a liquid, a biological material, a DNA strand, a bioactive agent, a toxin, or combinations thereof.  
     
     
         109 . The cantilevered probe array system of  claim 98 , wherein the circuit detects cantilever bending.  
     
     
         110 . The cantilevered probe array system of  claim 98  wherein the excitation voltage generator comprises an adjustable frequency generator that is scanned through a predetermined frequency range.  
     
     
         111 . The cantilevered probe array system of  claim 98  wherein the signal detector comprises an impedance analyzer that is scanned through a resonant frequency of at least one cantilevered probe in the cantilevered probe array.  
     
     
         112 . The cantilevered probe array system of  claim 98  wherein the excitation voltage generator comprises an oscillator circuit operating at a resonant frequency of at least one cantilevered probe in the cantilevered probe array.  
     
     
         113 . The cantilevered probe array system of  claim 97 , at least one cantilevered probe of the plurality of cantilevered probes comprising at least one chemical sensitive coating material applied to the at least one cantilevered probe.  
     
     
         114 . The cantilevered probe array system of  claim 113 , wherein the at least one chemical sensitive coating material is a first chemical sensitive coating material applied to a first cantilevered probe and a second chemical sensitive coating material applied to a second cantilevered probe in the cantilevered probe array.  
     
     
         115 . The cantilevered probe array system of  claim 114 , wherein the first and second chemical sensitive coating materials are different.  
     
     
         116 . The cantilevered probe array system of  claim 114 , wherein the resistive heaters formed on the first and second cantilevered probes are individually controllable.  
     
     
         117 . The cantilevered probe array system of  claim 113 , wherein the chemical-sensitive coating material comprises an epoxy resin, a fluoropolymer, a gold layer, a palladium layer, an alcohol-absorbent polymer, a water-absorbent material, a chemical-sensitive polymer, a chemical-sensitive layer, a biosensitive material, a thiol, or combinations thereof.  
     
     
         118 . The cantilevered probe array system of  claim 113  wherein the chemical-sensitive coating material is applied to at least a portion of the at least one cantilevered probe.  
     
     
         119 . The cantilevered probe array system of  claim 113  wherein the chemical-sensitive coating material is an epoxy resin, a fluoropolymer, a gold layer, a palladium layer, an alcohol-absorbent polymer, a water-absorbent material, a chemical-sensitive polymer, a chemical-sensitive layer, a biosensitive material, a thiol, or combinations thereof.  
     
     
         120 . The cantilevered probe array system of  claim 113  wherein the chemical-sensitive coating material comprises one of a dipped coating, a sprayed coating, or a dispensed coating disposed on at least a portion of the at least one cantilevered probe.  
     
     
         121 . The cantilevered probe array system of  claim 113  wherein the chemical-sensitive coating material comprises a masked coating disposed on a portion of the at least one cantilevered probe.  
     
     
         122 . The cantilevered probe array system of  claim 113  wherein the chemical-sensitive coating material comprises a non-homogeneous coating material applied to a set of cantilevered probes in the cantilevered probe array.  
     
     
         123 . The cantilevered probe array system of  claim 97  wherein at least a portion of the plurality of cantilevered probes in the cantilevered probe array is frequency-differentiated.  
     
     
         124 . The cantilevered probe array system of  claim 97  wherein at least one of the plurality of cantilevered probes is at least partially made from one or more materials comprising a piezoelectric material, silicon, polysilicon, silicon nitride, a metal, a metal alloy, a metal film, a metal sheet, a ceramic material, an ionic compound, a zinc oxide film, a PZT film, a polymeric layer, or combinations thereof.  
     
     
         125 . The cantilevered probe array system of  claim 97  wherein the cantilevered probe array is actuated with an excitation voltage applied across the piezoelectric layer of each of the plurality of cantilevered probes.  
     
     
         126 . The cantilevered probe array system of  claim 97  further comprising a cantilevered probe connected in series with the cantilevered probe array.  
     
     
         127 . The cantilevered probe array system of  claim 97  further comprising a cantilevered probe connected in parallel with the cantilevered probe array.  
     
     
         128 . The cantilevered probe array system of  claim 97  further comprising a cantilevered probe connected in series with the cantilevered probe array and a cantilevered probe connected in parallel with the cantilevered probe array.  
     
     
         129 . The cantilevered probe array system of  claim 97  further comprising a reference cantilevered probe in the cantilevered probe array, wherein the reference cantilevered probe provides a reference signal when the cantilevered probe array is exposed to the target chemical species.  
     
     
         130 . The cantilevered probe array system of  claim 97  further comprising a species attraction electrode disposed on at least one cantilevered probe in the cantilevered probe array to allow application of a species attraction potential.  
     
     
         131 . The cantilevered probe array system of  claim 97  further comprising an enclosure including the cantilevered probe array, an inlet port, and an outlet port; wherein the target chemical species enters through the inlet port, is exposed to the cantilevered probe array, and exits through the outlet port.  
     
     
         132 . The cantilevered probe array system of  claim 97  further comprising a transport mechanism for transporting the target chemical species to the cantilevered probe array.  
     
     
         133 . The cantilevered probe array system of  claim 97  further comprising a concentrator to concentrate the target chemical species proximal to the cantilevered probe array.  
     
     
         134 . The cantilevered probe array system of  claim 97 , wherein the resistive heaters are individually controllable.  
     
     
         135 . The cantilevered probe array system of  claim 97 , wherein the first and second electrodes are adjacent the piezoelectric layer.  
     
     
         136 . The cantilevered probe array system of  claim 97 , wherein the first electrode is located on a first side of the piezoelectric layer and the second electrode is located on a second side of the piezoelectric layer.  
     
     
         137 . The cantilevered probe array system of  claim 136 , wherein the first and second sides are opposite one another.  
     
     
         138 . The cantilevered probe array system of  claim 97 , wherein at least one of the plurality of cantilevered probes is at least partially made from one or more materials comprising a metal, a metal alloy, or combinations thereof.  
     
     
         139 . The cantilevered probe array system of  claim 97 , wherein at least one of the plurality of cantilevered probes is at least partially made from one or more materials comprising silicon, polysilicon, silicon nitride, or combinations thereof.  
     
     
         140 . The cantilevered probe array system of  claim 97 , wherein at least one of the plurality of cantilevered probes is at least partially made from one or more materials comprising a polymeric layer.  
     
     
         141 . The cantilevered probe array system of  claim 97 , wherein at least one of the plurality of cantilevered probes is at least partially made from one or more materials comprising a piezoelectric material.  
     
     
         142 . The cantilevered probe array system of  claim 97 , wherein at least one of the plurality of cantilevered probes is at least partially made from one or more materials comprising PZT.  
     
     
         143 . The cantilevered probe array system of  claim 97 , wherein at least one of the plurality of cantilevered probes is at least partially made from one or more materials comprising zinc oxide.  
     
     
         144 . The cantilevered probe array system of  claim 97 , wherein at least one of the plurality of cantilevered probes is at least partially made from one or more materials comprising zinc oxide and the chemical-sensitive coating material comprises an epoxy resin, a fluoropolymer, a gold layer, a palladium layer, an alcohol-absorbent polymer, a water-absorbent material, a chemical-sensitive polymer, a chemical-sensitive layer, a biosensitive material, a thiol, or combinations thereof.  
     
     
         145 . A system for sensing a chemical species, comprising: 
 an enclosure, the enclosure having an inlet port to allow ingression of a chemical species into the enclosure and an outlet port to allow egression of the chemical species out from the enclosure;    a cantilevered probe array coupled to the enclosure, the cantilevered probe array comprising a plurality of cantilevered probes, each of the plurality of cantilevered probes comprising: 
 a piezoelectric layer;  
 a first electrode in electrical communication with the piezoelectric layer;  
 a second electrode in electrical communication with the piezoelectric layer;  
 a resistive heater;  
   a first electrical lead;    a second electrical lead, wherein the first and second leads are in electrical communication with the piezoelectric layer of each of the plurality of cantilevered probes; and    a circuit coupled to the cantilevered probe array.    
     
     
         146 . The system of  claim 145  wherein at least a portion of the plurality of cantilevered probes in the cantilevered probe array is frequency-differentiated.  
     
     
         147 . The system of  claim 145  wherein the plurality of cantilevered probes in the cantilevered probe array is electrically connected to a pair of cantilevered probe array drive pads.  
     
     
         148 . The system of  claim 145  further comprising a controller in communication with the circuit; wherein the controller receives a shifted signal from a set of cantilevered probes in the cantilevered probe array, and wherein the chemical species is determined based on the shifted signal.  
     
     
         149 . The system of  claim 145  further comprising a reference cantilevered probe in the cantilevered probe array, wherein the reference cantilevered probe provides a reference signal when the cantilevered probe array is exposed to the chemical species.  
     
     
         150 . The system of  claim 145  further comprising a species attraction electrode disposed on at least one cantilevered probe in the cantilevered probe array to allow application of a species attraction potential.  
     
     
         151 . The system of  claim 145  further comprising a transport mechanism for transporting the chemical species to the cantilevered probe array.  
     
     
         152 . The system of  claim 145  further comprising a concentrator for concentrating the chemical species proximal to the cantilevered probe array.  
     
     
         153 . The system of  claim 145 , wherein the circuit is coupled to the piezoelectric layer of at least a portion of the plurality of cantilevered probes and the circuit comprises an excitation voltage generator in electrical communication with the piezoelectric layer of each of the cantilevered probes of the at least a portion of the plurality of cantilevered probes, and a signal detector in electrical communication with the piezoelectric layer of each of the cantilevered probes of the at least a portion of the plurality of cantilevered probes; wherein at least one cantilevered probe in the cantilevered probe array exhibits a shifted signal that is detected by the signal detector when the cantilevered probe array is exposed to the chemical species and the at least one cantilevered probe is moved by the circuit.  
     
     
         154 . The system of  claim 145 , wherein the first and second electrodes are adjacent the piezoelectric layer.  
     
     
         155 . The system of  claim 145 , wherein the first electrode is located on a first side of the piezoelectric layer and the second electrode is located on a second side of the piezoelectric layer.  
     
     
         156 . The system of  claim 155 , wherein the first and second sides are opposite one another.  
     
     
         157 . The method of  claim 49 , wherein applying the coating material comprises patterning the coating material photolithographically.  
     
     
         158 . The method of  claim 69 , further comprising, prior to exposing a self-sensed cantilevered probe array to a target chemical species, scanning through resonant frequencies of the cantilevered probes array to establish a baseline.