Molecular analysis using micro electro-mechanical sensor devices

Abstract

Analysis instruments and sensors, particularly micro-electro mechanical sensor (MEMS) devices, for molecular analysis of chemicals and other materials, including, for example, polymers, drugs, nanomaterials, biological samples including proteins, and environmental samples including water suspected of contamination, and the like in vapor, liquid, and/or solid form.

What is claimed is: 
     
         1 . A sensor device, comprising:
 an array comprising at least one reference cell and a plurality of sensor cells configured for differential thermal analysis, the plurality of sensor cells arranged in at least one row and at least one column, at least one sensor cell of the plurality of sensor cells comprising:
 a heating element configured to heat the at least one sensor cell; and 
 a temperature sensing element configured to sense a temperature of the at least one sensor cell; and 
   a controller configured to drive the heating element of the at least one sensor cell and sense an output signal from at least one of the temperature sensing elements; and   a processor configured to sense an output signal from the temperature sensing element of the at least one sensor cell and determine a presence of at least one analyte based on the output signal.   
     
     
         2 . The sensor device of  claim 1 , wherein the heating element and the temperature sensing element are the same. 
     
     
         3 . The sensor device of  claim 1 , wherein the at least one sensor cell comprises a suspended platform. 
     
     
         4 . The sensor device of  claim 3 , wherein the suspended platform comprises a microbridge structure. 
     
     
         5 . The sensor device of  claim 4 , wherein the suspended platform further comprises a heat spreader. 
     
     
         6 . The sensor device of  claim 3 , wherein the suspended platform comprises a cantilever. 
     
     
         7 . The sensor device of  claim 1 , wherein:
 the heating element of the at least one sensor cell comprises a resistive element having a serpentine shape; and   the temperature sensing element of the at least one sensor cell comprises another resistive element having a serpentine shape.   
     
     
         8 . The sensor device of  claim 7 , wherein the heating element of the at least one sensor cell is disposed on a different layer of the at least one sensor cell than the temperature sensing element of the at least one sensor cell. 
     
     
         9 . The sensor device of  claim 1 , wherein the controller is configured to maintain a temperature of the at least one sensor cell by modifying a power provided to the heating element of the at least one sensor cell. 
     
     
         10 . The sensor device of  claim 1 , wherein the at least one reference cell comprises a single reference cell for the plurality of sensor cells in the array. 
     
     
         11 . The sensor device of  claim 1 , wherein the at least one reference cell comprises a reference cell for each sensor cell of the plurality of sensor cells. 
     
     
         12 . The sensor device of  claim 1 , wherein the processor is configured to:
 perform thermal analysis of the at least one sensor cell; and   determine a mass adsorbed or absorbed onto at least one resonating sensor cell.   
     
     
         13 . The sensor device of  claim 1 , wherein at least one of the heating element and the temperature sensing element of the at least one sensor cell comprises a thin film resistor. 
     
     
         14 . The sensor device of  claim 1 , wherein each of the heating element and the temperature sensing element of the at least one sensor cell comprises a thin film resistor. 
     
     
         15 . The sensor device of  claim 14 , wherein the thin film resistor comprises tungsten, titanium tungsten, or nickel chromium. 
     
     
         16 . The sensor device of  claim 14 , wherein at least one of the heating element and the temperature sensing element of the at least one sensor cell comprises silicon, polysilicon, platinum, nichrome, or tungsten. 
     
     
         17 . The sensor device of  claim 1 , wherein the at least one sensor cell and the at least one reference cell are the same. 
     
     
         18 . The sensor device of  claim 17 , wherein the controller is configured to:
 drive the heating element according to a first temperature cycle while analyte is present on the at least one sensor cell; and   drive the heating element according to a second temperature cycle after removing analyte from the at least one sensor cell.   
     
     
         19 . The sensor device of  claim 18 , wherein the processor is configured to:
 receive a first signal from the temperature sensing element during the first temperature cycle; and   receive a second signal from the temperature sensing element during the second temperature cycle.   
     
     
         20 . The sensor device of  claim 19 , wherein the processor is configured to compare the second signal to the first signal. 
     
     
         21 . The sensor device of  claim 18 , wherein the controller is further configured to drive the heating element according to a third temperature cycle to clean the at least one sensor cell prior to driving the heating element after removing analyte from the at least one sensor cell. 
     
     
         22 . The sensor device of  claim 21 , wherein the controller is configured to drive the heating element according to a fourth temperature cycle responsive to the processor determining that a difference between the second signal and the third signal is greater than a predetermined amount. 
     
     
         23 . The sensor device of  claim 1 , wherein the heating element comprises a doped electrically conductive portion extending along opposing edges of the at least one sensor cell, the doped electrically conductive portion extending from a fixed end of the at least one sensor cell toward a free end thereof. 
     
     
         24 . The sensor device of  claim 1 , wherein the at least one sensor cell comprises a cantilever comprising low resistance rails along opposing sides thereof, the low resistance rails comprising a doped region. 
     
     
         25 . The sensor device of  claim 24 , further comprising a gap proximate a base of the cantilever, the gap located between the low resistance rails. 
     
     
         26 . The sensor device of  claim 24 , further comprising portions of doped silicon extending between the low resistance rails and portions of undoped silicon separating adjacent portions of the doped silicon. 
     
     
         27 . The sensor device of  claim 1 , wherein the at least one sensor cell comprises a cantilever and the heating element comprises a serpentine shaped resistive heater. 
     
     
         28 . The sensor device of  claim 1 , wherein the at least one sensor cell comprises a cantilever comprising silicon, the cantilever including a plurality of slots extending from opposing sides. 
     
     
         29 . The sensor device of  claim 28 , wherein a spacing between adjacent slots of the plurality of slots is variable. 
     
     
         30 . The sensor device of  claim 28 , wherein the at least one slot of the plurality of slots has a different width than other slots of the plurality of slots. 
     
     
         31 . The sensor device of  claim 1 , wherein the at least one sensor cell comprises a cantilever and wherein the heating element of the cantilever comprises a U-shape. 
     
     
         32 . The sensor device of  claim 1 , the at least one sensor cell comprises a cantilever and wherein the heating element and the temperature sensor element are coplanar and located adjacent each other. 
     
     
         33 . The sensor device of  claim 1 , wherein each sensor cell of the plurality of sensor cells comprises a cantilever, wherein the cantilevers are arranged in an alternating pattern, a free end of each cantilever located proximate a fixed end of an adjacent cantilever and wherein the fixed end of the each cantilever is adjacent the free end of an adjacent cantilever, adjacent cantilevers separated by a gap having a serpentine shape. 
     
     
         34 . A method of detecting an analyte by a differential thermal analysis, the method comprising:
 receiving an analyte in a sensor cell in a sensor device comprising a plurality of sensor cells configured for differential analysis and arranged in at least one row and at least one column;   heating a heating element of at least one sensor cell;   after heating the heating element of the at least one sensor cell, sensing a response of the at least one sensor cell with a temperature sensing element of the at least one sensor cell;   sensing a response of at least one reference cell that has been heated in a same manner as the at least one sensor cell; and   determining, with a processor, a presence of at least one analyte based, at least in part, on the sensed response of the at least one sensor cell relative to the sensed response of the at least one reference cell.   
     
     
         35 . The method of  claim 34 , further comprising sensing a temperature of at least one of the heating element and a temperature sensing element of the at least one sensor cell. 
     
     
         36 . The method of  claim 35 , wherein sensing a temperature of at least one of the heating element and a temperature sensing element of the at least one sensor cell comprises determining a resistance of the heating element. 
     
     
         37 . The method of  claim 34 , further comprising selecting the at least one reference cell to comprise the same cell as the at least one sensor cell, wherein heating a heating element of at least one sensor cell comprises:
 driving the heating element according to a first temperature cycle while analyte is present on the at least one sensor cell; and   after removing analyte from the at least one sensor cell, driving the heating element according to a second temperature cycle.   
     
     
         38 . The method of  claim 37 , wherein with a processor, a presence of at least one analyte based, at least in part, on the sensed response of the at least one sensor cell relative to the sensed response of the at least one reference cell comprises comparing the second signal to the first signal. 
     
     
         39 . The method of  claim 37 , further comprising driving the heating element according to a third temperature cycle to clean the at least one sensor cell prior to driving the heating element after removing analyte from the at least one sensor cell.