WO2003095616A2 - Capteurs bionems de dynamique et reseaux de capteurs bionems immerges dans des fluides - Google Patents

Capteurs bionems de dynamique et reseaux de capteurs bionems immerges dans des fluides Download PDF

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WO2003095616A2
WO2003095616A2 PCT/US2003/014284 US0314284W WO03095616A2 WO 2003095616 A2 WO2003095616 A2 WO 2003095616A2 US 0314284 W US0314284 W US 0314284W WO 03095616 A2 WO03095616 A2 WO 03095616A2
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nems
fluid
layer
cantilever
ligand
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PCT/US2003/014284
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WO2003095616A3 (fr
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Michael L. Roukes
Scott E. Fraser
Jerry E. Solomon
Michael C. Cross
Jessica L. Arlett
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California Institute Of Technology
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Priority to US10/502,551 priority Critical patent/US7375321B2/en
Priority to AU2003241377A priority patent/AU2003241377A1/en
Priority to EP03731110A priority patent/EP1502279A2/fr
Priority to JP2004503610A priority patent/JP2006512564A/ja
Publication of WO2003095616A2 publication Critical patent/WO2003095616A2/fr
Priority to US10/826,007 priority patent/US7302856B2/en
Publication of WO2003095616A3 publication Critical patent/WO2003095616A3/fr

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/48—Biological material, e.g. blood, urine; Haemocytometers
    • G01N33/50—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing
    • G01N33/53—Immunoassay; Biospecific binding assay; Materials therefor
    • G01N33/543—Immunoassay; Biospecific binding assay; Materials therefor with an insoluble carrier for immobilising immunochemicals
    • G01N33/54366—Apparatus specially adapted for solid-phase testing
    • G01N33/54373—Apparatus specially adapted for solid-phase testing involving physiochemical end-point determination, e.g. wave-guides, FETS, gratings

Definitions

  • the invention relates to the field of fluidic bioNEMS devices and methods of operating the same.
  • what is needed is some way of reducing the size of the cantilever to NEMS dimensions to offer the needed temporal response, small volume and sensitivity to single molecules needed to build a device with single cell capability.
  • placing a NEMS cantilever in solution and at room temperature will call for a revision of detection strategy from those usually employed for either CFM or NEMS.
  • the fluid will damp the NEMS cantilever making resonance detection impossible, and the thermal energy of the solution will buffet the cantilever.
  • NEMS cantilever will allow detection of the presence of a chemical bond by the restriction it produces in the otherwise large thermally driven motion of the cantilever using an integral sensor.
  • Microarray technologies have provided significant recent advances in analyzing protein receptors and their ligands, as well as in analyzing gene expression profiles. For example, microarrays of a few thousand targets have become a major technique used by the drug discovery industry. These microarrays are created by photolithography, by microstamping, or by microdotting, resulting in an array of spots (20-1 OODrn) on a substrate. The array is typically read by superfusing a fluorescently labeled analyte, over the array and determining the amount of binding by scanning the array with a micro-fluorimeter. Although these approaches are becoming increasingly widespread, the large size of the reader instrumentation and the intrinsic limitations of the fluorescence analysis employed make them completely inappropriate for applications in which both portability and robust performance are required.
  • Another goal of the proposed studies is to develop a new technology of biochips at the nanoscale (BioNEMS) that is capable of sensing the binding of single biological molecules to their receptors.
  • a growing literature of chemical force microscopy (CFM) has shown that a modified AFM can be tailored to measure the binding force of interactions ranging from single hydrogen bonds and single receptor-ligand interactions to single covalent bonds. The range of these forces are well within the capability of AFM instrumentation to detect; however, an AFM cantilever in solution does not have the temporal response characteristics needed to permit the binding and unbinding of biological ligands and their receptors to be followed reliably. Perhaps even more significant is the substantial size of the equipment required for performing AFM/CFM, and the well-known sensitivity of AFM to air-borne and surface vibrations.
  • NEMS the motions of the NEMS cantilevers will be used to follow binding and unbinding events.
  • the basic idea is that a cantilever that is not coupled at its tip by a receptor-ligand pair will fluctuate in its position more dramatically than a cantilever that is restricted by a ligand-receptor pair. Strong ligand-receptor bonds can partially arrest the cantilever motion for considerable time ( ⁇ t on for the ligand-receptor pair); even weak interactions will alter the statistics of cantilever motion.
  • NEMS in this specification is used to mean devices with at least one dimension which is equal to or smaller than one micron.
  • NEMS nanoelectrative electrospray senor
  • the "NEMS” device may have one or more other dimensions larger than one micron.
  • the small size of the NEMS devices permit them to be dramatically more responsive to the kinetics of binding and unbinding.
  • BioNEMS are thus poised by the invention to truly move our analysis of biomolecules to the stochastic limit.
  • One of the powers of this approach is that it exploits the thermal motion of the cantilever, normally a major limitation in AFM, as a driving force.
  • the noise of cantilever motion becomes smaller as cantilever size is decreased.
  • the small size of NEMS devices permits an array of detectors ( ⁇ 500 cantilevers) to be constructed in a small active volume ( ⁇ 100pL). This latter advantage is of great significance, as it offers the promise of a technology for sensing the levels of RNA, proteins and second messengers present in single cells.
  • the BioNEMS approach of the invention offers a major reduction in the size and nature of the instrumentation needed for it to operate (in comparison to AFM/CFM).
  • the sensor for the motion of the cantilever will be integral to the NEMS cantilever, which eliminates the size and density limits that would be imposed by the optical detection of cantilever motion used in AFM. This will permit the BioNEMS cantilevers to be much smaller and to be dramatically more closely packed than is practical in AFM.
  • BioNEMS research effort outlined here will have several thrusts, ranging from fundamental to applied science, and the development on new nanoscale fluidic technology. Our goal is to develop, understand and, thereby, to refine the techniques for the construction of BioNEMS and then demonstrate their novel uses. Examples include:
  • the invention is defined as a submicron bioNEMS device comprising a support and a piezoresistive cantilever coupled to the support extending therefrom with a length I and having a width w and a tip, wherein the cantilever has a restriction portion of reduced width, b, and a length , and a biofunctionalized portion at or near the tip.
  • the restriction portion is comprised of multiple legs of reduced width, b, attached to the support. Preferably two legs are provided and are separated from each other by a distance of w - 2b.
  • the bioNEMS device further comprises a source of bias current applied to the restriction portion of the cantilever and where the magnitude of the bias current is limited by a maximal acceptable temperature increase at the biofunctionalized tip.
  • the maximal acceptable temperature increase at the biofunctionalized tip is approximately 1 degree K.
  • the invention is also an improvement in a piezoresistive bioNEMS device immersed in a fluid comprising at least one oscillating cantilever having a length I having a magnitude chosen to minimize background Johnson noise relative to signal strength generated by the piezoresistive bioNEMS device.
  • the signal strength is based on thermomechanical noise levels of the piezoresistive bioNEMS device in the fluid.
  • the piezoresistive cantilever has a width w, and a restriction portion of reduced width, b, wherein the reduced width, b, is chosen to reduce Johnson noise relative to the signal strength generated by the piezoresistive bioNEMS device.
  • the invention is further characterized as an improvement in a biofunctionalized bioNEMS device immersed in a fluid comprising a receptor disposed on the bioNEMS device for binding to a ligand of interest and a catalyst disposed on the bioNEMS device with the receptor to enhance binding rate coefficients of the receptor with the ligand of interest.
  • the catalyst lowers the receptor-ligand binding activation energy.
  • the receptor is designed by forced evolution to preferentially bind with the ligand of interest.
  • the invention is also defined as a submicron device comprising a source of a carrier signal, a support, a piezoresistive cantilever coupled to the support and extending therefrom, and an element disposed on the cantilever and electromagnetically coupled to the source so that the cantilever is driven by the carrier signal from the source.
  • the element comprises a magnetic film disposed on the cantilever, and the source generates an electromagnetic signal coupled to the magnetic film.
  • the invention is an apparatus comprising a plurality of NEMS resonators or transducers, each of the NEMS transducers generating an output signal; and means or circuit for processing the plurality of corresponding output signals from the plurality of NEMS transducers to obtain a collective output signal.
  • the means averages the plurality of output signals so that the collective output signal is an average.
  • the means determines if a predetermined fraction of the plurality of output signals are above a threshold within a predetermined time window.
  • Each of the plurality of NEMS transducers is biofunctionalized and the means effectively increases ligand capture rates by only generating a collective output signal indicative of an increase ligand capture rate as compared to a single one of the NEMS transducers.
  • the invention is described as an apparatus operating in a fluid comprising a plurality of NEMS transducers immersed in the fluid forming an array of adjacent transducers, each of the NEMS transducers generating an output signal, the motion of two adjacent NEMS transducers being coupled to each through the fluid in which the adjacent NEMS transducers are immersed.
  • ⁇ -C n (t) -k B TX n (t) fort>0 at where k ⁇ is the Boltzman constant, T is the temperature of the fluid, t is time, and
  • the invention is an apparatus operating in a fluid comprising a microfluidic flow channel for carrying a flow of the fluid, and at least one N ⁇ MS transducer disposed in the microfluidic flow channel so that a characteristic of the fluid is sensed by the N ⁇ MS transducer.
  • the N ⁇ MS transducer is biofunctionalized and the characteristic of the fluid is sensed by the N ⁇ MS transducer is the presence or absence within the fluid of a ligand to which the N ⁇ MS transducer has been biofunctionalized.
  • the apparatus further comprises a plurality of the N ⁇ MS transducers, each of which is disposed in common in the flow channel.
  • the apparatus further comprises a plurality of flow channels among which the plurality of NEMS transducers re distributed.
  • the plurality of NEMS transducers are surface fabricated or membrane fabricated.
  • the invention includes a method of fabricating a bioNEMS device from a membrane comprising the steps of providing a heterostructure comprising a wafer layer, an etch stop layer on the wafer layer, a NEMS device layer on the etch stop layer, and a piezoresistive layer on the NEMS device layer. Trenches are etched through the wafer layer to the etch stop layer to define an area which will become a membrane in which the NEMS device will be defined. The etch stop layer is removed from the bottom of the trenches to the device layer to form the membrane. Conductive contacts are selectively formed on the piezoresistive layer of the membrane by electron beam lithography.
  • Regions are selectively formed which will become biofunctionalized on the piezoresistive layer of the membrane by electron beam lithography.
  • a NEMS device is selectively formed on the piezoresistive layer of the membrane by electron beam lithography which include the region which will become biofunctionalized.
  • the membrane is selectively plasma etched to remove unmasked portions to define a suspended NEMS device.
  • a flow channel is selectively molded in an elastomeric layer disposed around the membrane. Selected regions are biofunctionalized on the NEMS
  • the step of providing a heterostructure further comprises polishing the wafer layer to promote adhesion to the elastomeric layer and thinning the wafer layer.
  • the step of selectively plasma etching the membrane to remove unmasked portions to define a suspended NEMS device comprises selectively vertically plasma etching away unmasked portions of the NEMS device layer.
  • the step of selectively molding a flow channel in an elastomeric layer disposed around the membrane comprises selectively disposing a photoresist layer to define the flow channel, disposing an elastomeric layer on the selectively disposed photoresist layer, and removing the photoresist layer to define the flow channel.
  • the invention discloses a NEMS device for operating in a fluid comprising a resonating member having a tip immersed in the fluid, a linking molecule attached to the tip; and a fluffball attached to the linking molecule and providing a damping force to dissipate noise applied to the member from the fluid.
  • the invention also includes methods for operating the NEMS devices disclosed above.
  • Fig. 1 is a graph of the observed improvement in the strength of the fluid coupled thermomechanical noise relative to the Johnson noise with all other dimensions fixed.
  • Fig. 2 is a graph of the fluid damped thermomechanical noise.
  • Fig. 4 is a diagrammatic side elevational view of the cantilever in microscopically enlarged scale.
  • Fig. 5 is a graph of the fractional receptor occupancy as a function of nonspecific binding events.
  • Fig. 6 is a diagram of a detector known as a " phase-detector” or “lock-in amplifier”, or a correlation receiver.
  • Fig. 7 is a graph illustrating detector performance P d as a function of SNR.
  • Fig. 8a is a diagrammatic top plan view of a double cantilever system.
  • Fig. 8b is a diagrammatic side cross-sectional view of the system of Fig. 8a.
  • Fig. 8c is a diagrammatic top plan view of another embodiment wherein the cantilevers are ligand coupled.
  • Fig. 9 is a graph of the fluid velocity component parallel to an oscillating cantilever as a function of distance, r.
  • Fig. 10 is a cross sectional schematic side view of a piezoresistive cantilever coupled to a microfluidic flow channel
  • Figs. 11a - 11c is a diagrammatic perspective view in increasing magnification of the array of cantilevers shown in Fig. 10
  • Fig. 12a is a scanning electron microscopic photograph of a bioMEMS transducer.
  • Fig. 12b is a diagram of the top plan view of the transducer of Fig. 12a.
  • Figs. 13a - 13m are a series of diagrams illustrating a method for fabricating a bioNEMS fluidic sensor from a membrane.
  • Fig. 14 is a diagram modeling the dynamic action of a cantilever with a molecularly bound fluffball as an added damper.
  • the illustrated embodiment is directed to the constraints upon the level of current bias that can be applied to a piezoresistive BioNEMS device in fluid.
  • the largest practical level of bias current is determined by the maximum temperature rise in the BioNEMS which is deemed acceptable.
  • the bioNEMS transducer or cantilever 10 shown in perspective view in the microphotograph Fig. 12a and in the top plan view diagram of Fig. 12b shall be assumed, which can be analogized as having the form of "a diving board with a cutout at its base".
  • the geometry of the transducer 10 is to be entirely general and includes any type cantilever, doubly clamped beam, paddle or any other submicron oscillating structure.
  • the geometry of the device 10 causes maximization to occur predominantly within a constriction region 12 comprised of one or more legs 20 of width b, as shown in Fig.
  • cantilever 16 which region 12 allows for enhanced or variably designed flexural stiffness of cantilever 16 without restricting the fluidic damping characteristics of cantilever 16 dependent on its over length I and width w. It is also to be understood that cantilever 16 will have conventional electrodes (not shown) provided whereby a conventional external measurement circuit (not shown) providing a bias current may measure the change in piezoresistivity of legs 20 as they flex. In addition, an external driving force may or may not be applied in a conventional manner to cantilever 16 depending on the application and design choice.
  • a temperature rise of order 1 K is tolerable at the biofunctionalized tip 14 of the cantilever 16, which has a length, I, a width, w, and a thickness, t, resonant frequency in vacuum ⁇ 0 l2 ⁇ and force constant K.
  • cantilever 16 is made of silicon and assumed to be immersed in water, but any nanomachinable material may be employed and any ambient fluid may be contemplated.
  • the distance x is measured from the connection of cantilever 16 to support 17 towards its tip 14. For x > Ii, a rough estimate of the heat loss to the water or fluid in which device 10 is immersed may be obtained
  • responsivity R I G of about 8 ⁇ V/nm.
  • the second cantilever 16 in Table 1 we allow the same 12K maximal temperature rise in the constricted region 12, this coincides with a temperature rise of 0.04K at the tip 14 and occurs for a current of 75 ⁇ A.
  • G 5.2x10 9 ⁇ /m.
  • the expected responsivity is 390 ⁇ V/nm.
  • thermomechanical noise For applications in which device 10 is driven by fluid-coupled thermomechanical noise in the fluid in which it is immersed, it is beneficial that this signal be maximized relative to the background Johnson noise in device 10.
  • the relative strength of these two sources of thermal noise is determined by the cantilever's 16 dimensions. These dimensions enter both into the magnitude of the fluidic damping which determines the spectral density of the fluid-coupled thermomechanical noise in the force domain and into the response function of the cantilever 16 (through the damping, effective mass, gauge factor, spring constant and allowed current for the same amount of heating at the tip).
  • Increasing the total length I and width w of the cantilever 16 increases the coupling to the fluid, increasing both the fluidic damping and the cooling efficiency; also leading to an improved signal-to-noise ratio.
  • Fig. 2 is a graph of the fluid damped thermomechanical noise, which is predicted to increase relative to the background Johnson noise as the cantilever length is increased. For a length of 35 ⁇ m, the fluid damped thermomechanical noise has a peak an order of magnitude larger than the background Johnson noise.
  • the bias current was chosen such that the estimated temperature rise at the tip 14 not exceed 1 °C and that at the point of maximal temperature in the legs 20 did not exceed 50°C.
  • the bias currents used and estimated temperature rises are summarized in Table 2. Table 2
  • thermomechanical noise is dependent on the fluid viscosity.
  • device 10 is biofunctionalized by having bioreceptor molecules 24 attached to or near tip 14 of cantilever 16 as diagrammatically shown in Fig. 4. Since one of the fundamental features of NEMS device 10 is the use of biological receptor molecules 24 attached to a "functionalized" region of an elastic cantilever 16, it is important that the receptor-ligand binding reaction have the highest possible rate coefficient (reaction probability) for the target ligand 22 of interest. However, it is well known that biologically expressed receptor molecules 24 do not in general have the highest possible binding rate coefficients for their target ligands, since evolution does not select for this attribute. Thus it will be useful to examine various methods for enhancing the binding rate coefficients for receptors 24 of interest in applications of the NEMS device 10.
  • One possible approach is to use the equivalent of catalyzed reaction by finding specific molecules which, when in close association with a particular specie of receptor 24, lower the receptor-ligand binding activation energy. Since rate coefficients, and thus reaction probabilities, are very sensitive to activation energy, e.g. have an exponential dependence, lowering this energy by even relatively small amounts yields large increases in the binding rate coefficients.
  • the idea here is to first attach a layer of these "catalyst" molecules 26 to a small functionalized region 28 of the cantilever 16, and then attach the receptors 24 specific to the target ligand 22 of interest.
  • the basic concept of this approach is shown in Fig. 4. The choice a catalyst in any given instance would be dictated by the ligand-receptor pair according well known principles.
  • a second and probably viable approach is to design the receptor molecules 24 whose binding rate coefficient is maximized with respect to a specific ligand 22 of interest.
  • design is understood here to mean that one uses forced evolution, biochemical techniques to select for genes that express the desired receptor 24 with higher and higher binding affinities for the chosen ligand 22 as one goes through multiple rounds of "evolving" the gene. This is usually accomplished by inserting multiple copies of the gene for a receptor 24 of interest into the genome of a particular bacterium so that the bacteria will express this receptor on their cell surfaces. Binding affinity assays are then carried out on the first generation of bacteria, and only those with the highest binding affinities are kept for the next round of the" evolutionary" cycle.
  • Fig. 5 is a graph which shows an example of the possible effects of
  • the curve 30 is the fractional occupancy of functionalized sites 28 by target ligand 22, while curve 32 represents the fractional occupancy by both target 22 and background ligand molecules 32.
  • the conditions used were: (1) 1000 target ligand molecules 22; (2) 100 receptor molecules 24; and (3) 10,000 background ligand molecules 32; with a nonspecific binding affinity of 200 times less than for the target ligand molecules 22.
  • the effects of non-specific binding competition for receptors 24 could be significant for device 10 as shown in Fig. 5.
  • the correlation detector of Fig. 6 is comprised of a narrowband filter 34 which takes its input, r(t), from device 10.
  • a reference signal from oscillator 36 is mixed by mixer 38 with the output of filter 34.
  • the mixed filtered signal is input into low pass filter 40 and then coupled to a thresholding and decision circuit 42, which determines first if the signal is qualified as a valid or information-bearing signal and then if qualified a decision algorithm is implemented to determine if device 10 has or has not detected the ligand-receptor interaction of interest.
  • These circuits may be implemented in analog or digital signal processors or computers as controlled by hardware design, firmware or software as devised by conventional design options.
  • FIG. 8a shows two possible embodiments that can generate signals of the form of Eqn. 1.
  • carrier injection is achieved by mechanically driving an unfunctionalized cantilever 16a with no receptors at a fixed frequency, ⁇ o, and amplitude.
  • the functionalized cantilever 16b responds to the driver 16a through fluid dynamic coupling of the fluid in which the device 10 is immersed.
  • the driven cantilever 16b has a piezoresistive portion 46. Both cantilevers 16a and 16b are connected to supports 48, which in turn may be connected to substrates 44 or 50.
  • Figs. 8a - 8c the "no signal" case is where the cantilever 16b is constrained not to move significantly by “tacking” it to the substrate 44; the presence of "free” target ligand 22 results in breaking this condition through competitive binding.
  • the side-by-side arrangement of Fig. 8a is not the preferred configuration. As a practical matter it is better to have the two cantilevers opposed, i.e., tip-to-tip.
  • Fig. 8c is a slightly different version of Figs. 8a and 8b, where the no-signal state has the two cantilevers 16 and 34 mechanically coupled through a ligand-receptor binding arrangement.
  • a different use of multiple cantilevers 16 is to utilize an array of N identical undriven cantilevers in either an averaging mode or a coincidence mode.
  • averaging mode we simply use the N outputs to obtain a V/V improvement in our estimate of the variance.
  • coincidence mode we use the constraint that some fraction of the N outputs must be above a threshold value within a fixed time window to be considered a "signal present" event. In both cases the method of using multiple cantilevers seeks to improve the ligand capture rate by increasing the number of available receptors 24.
  • the flow around a long cantilever 16 has quite different properties than the flow around a sphere, and this suggests a strategy for minimizing the fluidic correlations.
  • the low Reynolds number flow around a moving sphere is everywhere in phase with the motion of the sphere and falls off as 1/r.
  • a simple model of our cantilevers 16 is to approximate them as cylinders, long compared to the radius. In this case the Stokes results for the flow around infinite cylinders can be used.
  • R is typically about unity.
  • This velocity field is responsible for the motion of the second cylinder, so that there is a separation and frequency dependence to the motion of the second cylinder induced by the force on the first cylinder.
  • theorem which states the fluctuations present in a system is proportional to the damping in the system, this gives us a separation and frequency dependence to the noise correlation.
  • FIG. 9 shows in fact that the different quadratures of the velocity field have null points at different distances, suggesting that it might be possible to find parameters (cylinder separation/radius and frequency) corresponding to null points in the one or other phase of the fluid induced correlated noise.
  • the angular brackets denote an ensemble average, emphasizing again that a deterministic estimate, calculation, or experiment enables the stochastic motion to be quantified.
  • the susceptibility X- ⁇ 2 can be calculated from the Stokes velocity field plotted in Fig. 9, and so the noise correlations can be predicted, although not presented here.
  • FIG. 10 shows a schematic of a cross section of a device 10 with a cantilever 16 coupled to a microfluidic flow channel 52.
  • the region etched through the wafer 54 forms part of the final flow channel.
  • An entire array of cantilevers 16 can be fabricated within a single flow channel 54. It is also possible to have multiple channels 54 with different devices 10 in different channels 54 depending on the desired application. It is also possible to surface fabricate the flow channels 54 directly in the silicon. This is shown schematically for an array 56 of devices in Figs.
  • 11a - 11c which are three perspective views in increasingly enlarged scale showing a plurality of cantilevers 16 supported on parallel supports 48 forming rows of parallel cantilevers 16 in a single flow chamber 58 communicated with an inlet and outlet flow channel 54.
  • Figs. 13a - 13g show a flow diagram schematically depicting the steps involved in the fabrication of membrane-based BioNEMS devices 10. Fabrication of these devices begins with the side cross-sectional view of Fig. 13a with a silicon device layer 148 on insulator wafer 152, 154, such as a 375 nm Si0 2 layer 152 on a 675 ⁇ m Si layer 154.
  • the buried oxide layer 152 must be thick enough to serve as a stop layer in the etching step through the back of the wafer 154.
  • the Si device layer 148 should be of the desired thickness for the undoped portion of the silicon cantilever between 20nm and 100nm for most of the devices under consideration. In the illustrated embodiment an 80nm Si layer 148 is disposed beneath a 30nm heavily doped Si layer 150.
  • the resistivity of layer 148 should be high relative to that of the heavily doped layer 150 which will be grown. (10 ⁇ cm is sufficient).
  • the backside of the wafer 154 is polished. This is necessary for the adhesion of an elastomeric material thereto in which microfluidic channels 52 will be defined as described below.
  • the wafer 154 may be thinned at the same time which serves both to decrease the ultimate volume of the flow channel 52 and reduce the necessary thickness through which one must etch in a later etching step. A final wafer thickness of 300 ⁇ m is reasonable to maintain structural integrity of the wafer 154 while reducing the unnecessary material.
  • a layer of heavily boron doped silicon layer 150 is epitaxially grown on the top surface of layer 148, which layer 150 will form the conducting layer of the piezoresistor which forms part of the NEMS device 10. For most of the devices 10 this layer 150 is between 7nm and 30nm thick. The resistivity must be low compared to that of layer 148 below. A doping level of 4x10 19 cm “3 is typical.
  • the next step involves the fabrication of membranes by etching through the back of the wafer 154 as shown in the side cross-sectional view of Fig. 13b. This may be performed using a Bosch deep reactive ion etch (DRIE) to form trenches 158 through layer 154.
  • DRIE deep reactive ion etch
  • a photoresist or oxide mask 156 of approximately six microns is sufficient as shown in Fig. 13b. Membranes of 50 ⁇ m 2 have been used, but this is arbitrary and the dimensions to be used are determined by the application.
  • the oxide layer 152 directly under the silicon membrane 148 is then removed from the bottom of trenches 158 with hydrofluoric acid as shown in Fig. 13c to define an area which will become membrane 162.
  • Photolithography and metal deposition is next performed on the top side of the device 10 on layer 150, aligned to the membranes 162, to form the contact pads 160 as depicted in the top plan view of Fig. 13d which shows a plurality of dies being simultaneously formed. 30nm of chrome (as an adhesion layer) followed by 250 nm of Au are deposited in the desired pattern for the bond pads 160 to form ohmic contacts to the boron doped silicon layer 150.
  • Silicon ⁇ itride layer 174 (300nm) is then deposited over the Au followed by 200nm silicon dioxide layer 175 to passivate the devices 10 as seen in the top plan view of Fig. 13e followed by a layer 176 of chrome as seen in the top plan view of Fig. 13f to protect the silicon dioxide 175 during the fabrication process and provide electrical continuity across the step height formed by the passivating layers as shown in
  • Electron beam lithography is then used to pattern first the gold pads (not shown in drawings) at the tips 14 of where the cantilever 16 will be biofunctionalized and then the cantilevers 16 are patterned (on PMMA) followed by the evaporation of a 30nm layer 178 (not shown in drawings) of chromium and liftoff as shown in the perspective view of Fig. 13i.
  • This portion of the fabrication process involves two steps. First there is the step of disposing a gold square 180 (not shown in drawings) at what will be the tip 14 of the cantilever 16, which will be used for biofunctionalization along with alignment marks (not shown in drawings). The second step is a lithography step which is performed to mask the region which will comprise the cantilever 16 with chrome layer 178 (not shown in drawings).
  • the device 10 is suspended by means of a vertical plasma etch (NF 3 , Cl 2 , Ar) which removes the unmasked portions of the membrane defined in layers 150 and 148 resulting in a cantilever 16 as depicted in Fig. 13i and in top plan view as shown in Fig. 13j.
  • a wet etch is then used to remove the chromium mask 178 (not shown in drawings) and the sample is dried with a critical point dryer.
  • the wafer is diced as shown in the top plan view of Fig. 13k.
  • the microfluidic channels 52 are then fabricated from a silicone elastomer using a patterned photoresist as a mold, which photoresist is then etched away to define the actual flow channels defined in a molded elastomeric encapsulating body 182 as shown in Fig. 131.
  • the flow channels 52 are self-sealing with the silicon of device 10 when placed in an 85°C oven for 24 hours.
  • the device 10 or gold pad 180 is then biofunctionalized by conventional means as shown in Fig. 13m, such as by flowing a fluid through flow channels 52 which fluid carries receptor molecules which preferentially attach to gold pad 180.
  • a fluffball 60 which is nothing more than a large dissipative molecule, is provided with linking receptor molecules 62.
  • the fluffball 60 and linking molecule 62 are free floating in the liquid.
  • Linking molecule 62 is adapted to link to a ligand of interest.
  • Tip 14 is also biofunctionalized with receptors adapted to link to the ligand. Capture of the receptors on tip 14 of the ligand of interest with the receptor 62 and fluffball 60 attached will cause the damping coefficient of tip 14 to dramatically increase.
  • Fig. 14 is a mathematical model of a cantilever 16 of mass M having a fluff ball 60 attached to its tip 14 by a molecule 62 treated as a spring.
  • the fluffball 60 is devised to maximize dissipation and hence noise and is comprised of a star dendrimer.
  • Molecule 62 may be comprised of an alkane or a ligand chain.
  • the equation for the system of Fig. 14 is:
  • M is the mass of cantilever 16
  • y is the fluidic damping coefficient for cantilever 16
  • the spring constant of the cantilever 16 x the displacement of the cantilever tip 14
  • k m the effective spring constant of molecule 62
  • X d the displacement of fluffball 60
  • Y d is the fluidic damping coefficient for fluffball 60
  • F is the external force applied to cantilever 16.
  • the fluffball 60 is chosen so that its damping coeffiecient is as large as possible in order to maximize dissipation and hence the noise so that

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Abstract

L'invention concerne un dispositif bioNEMS comprenant un porte-à-faux piézorésistif qui présente des jambes flexibles le reliant à un support, et une partie biofonctionnalisée située au niveau de son embout. Un courant de polarisation appliqué sur les jambes est limité par une augmentation de température maximum acceptable au niveau de l'embout biofonctionnalisé. La longueur du porte-à-faux présente une magnitude sélectionnée afin de réduire au minimum le bruit thermique de fond. Un récepteur catalysé situé sur le dispositif se lie à un ligand dont le coefficient de liaison est amélioré. Ce catalyseur réduit l'énergie d'activation de liaison récepteur-ligand et est conçu par évolution forcée pour se lier de préférence au ligand. Un signal porteur est injecté par un film magnétique disposé sur le porte-à-faux qui est raccordé par voie électromagnétique à une source du signal porteur. Une pluralité de transducteurs raccordés fluidiquement au NEMS produisent une pluralité de signaux de sortie d'où est dérivé un signal de sortie collectif, par établissement d'une moyenne ou d'un seuil. Les dispositifs NEMS sont disposés dans des canaux d'écoulement microfluidiques et fabriqués dans une membrane. Une molécule de liaison est reliée à l'embout du transducteur et une structure dissipative de molécules est reliée à la molécule de liaison afin d'augmenter l'amortissement.
PCT/US2003/014284 2000-08-09 2003-05-07 Capteurs bionems de dynamique et reseaux de capteurs bionems immerges dans des fluides WO2003095616A2 (fr)

Priority Applications (5)

Application Number Priority Date Filing Date Title
US10/502,551 US7375321B2 (en) 2000-08-09 2003-05-07 Dynamics bionems sensors and arrays of bionems sensor immersed in fluids
AU2003241377A AU2003241377A1 (en) 2002-05-07 2003-05-07 Dynamics bionems sensors and arrays of bionems sensor immersed in fluids
EP03731110A EP1502279A2 (fr) 2002-05-07 2003-05-07 Capteurs bionems de dynamique et reseaux de capteurs bionems immerges dans des fluides
JP2004503610A JP2006512564A (ja) 2002-05-07 2003-05-07 動力学バイオｎｅｍｓセンサ及び流体内に浸漬されるバイオｎｅｍｓセンサのアレー
US10/826,007 US7302856B2 (en) 2003-05-07 2004-04-16 Strain sensors based on nanowire piezoresistor wires and arrays

Applications Claiming Priority (18)

Application Number Priority Date Filing Date Title
US37970802P 2002-05-07 2002-05-07
US37964502P 2002-05-07 2002-05-07
US37955202P 2002-05-07 2002-05-07
US37971002P 2002-05-07 2002-05-07
US37964302P 2002-05-07 2002-05-07
US37954302P 2002-05-07 2002-05-07
US37966002P 2002-05-07 2002-05-07
US37968102P 2002-05-07 2002-05-07
US37971102P 2002-05-07 2002-05-07
US60/379,543 2002-05-07
US60/379,711 2002-05-07
US60/379,681 2002-05-07
US60/379,643 2002-05-07
US60/379,710 2002-05-07
US60/379,552 2002-05-07
US60/379,645 2002-05-07
US60/379,708 2002-05-07
US60/379,660 2002-05-07

Related Parent Applications (1)

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PCT/US2003/014286 Continuation-In-Part WO2003095617A2 (fr) 2002-05-07 2003-05-07 Procede et appareil permettant d'obtenir une analyse de signal d'un resonateur ou d'un transducteur de bionems

Related Child Applications (2)

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PCT/US2003/014566 Continuation-In-Part WO2004041998A2 (fr) 2002-05-07 2003-05-07 Appareil et procede pour capteurs d'energie, de force et de masse nanomecaniques sous vide
US10/826,007 Continuation-In-Part US7302856B2 (en) 2003-05-07 2004-04-16 Strain sensors based on nanowire piezoresistor wires and arrays

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WO2003095616A3 WO2003095616A3 (fr) 2004-04-29

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JP (1) JP2006512564A (fr)
CN (1) CN1663014A (fr)
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Cited By (16)

* Cited by examiner, † Cited by third party
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US7302856B2 (en) 2003-05-07 2007-12-04 California Institute Of Technology Strain sensors based on nanowire piezoresistor wires and arrays
WO2008091294A2 (fr) * 2006-07-28 2008-07-31 California Institute Of Technology Système nanoélectromécanique polymère pour la physiologie cellulaire et système de positionnement de cellules microfabriquées pour micro-biocalorimètre
US7408147B2 (en) 2005-07-27 2008-08-05 Wisconsin Alumni Research Foundation Nanoelectromechanical and microelectromechanical sensors and analyzers
US7409851B2 (en) * 2005-03-29 2008-08-12 Cornell Research Foundation, Inc. Detection of small bound mass
US7434476B2 (en) 2003-05-07 2008-10-14 Califronia Institute Of Technology Metallic thin film piezoresistive transduction in micromechanical and nanomechanical devices and its application in self-sensing SPM probes
GB2432001B (en) * 2003-10-17 2009-04-15 Nevada System Of Higher Education Self-sensing array of microcantilevers for chemical detection
US7552645B2 (en) 2003-05-07 2009-06-30 California Institute Of Technology Detection of resonator motion using piezoresistive signal downmixing
US7694346B2 (en) 2004-10-01 2010-04-06 Board Of Regents Of The Nevada System Of Higher Education On Behalf Of The University Of Nevada Cantilevered probe detector with piezoelectric element
US7762719B2 (en) 2004-04-20 2010-07-27 California Institute Of Technology Microscale calorimeter
US7884324B2 (en) 2007-06-03 2011-02-08 Wisconsin Alumni Research Foundation Nanopillar arrays for electron emission
US8507845B2 (en) 2011-06-02 2013-08-13 Wisconsin Alumni Research Foundation Membrane detector for time-of-flight mass spectrometry
US8742333B2 (en) 2010-09-17 2014-06-03 Wisconsin Alumni Research Foundation Method to perform beam-type collision-activated dissociation in the pre-existing ion injection pathway of a mass spectrometer
US8750957B2 (en) 2004-06-01 2014-06-10 California Institute Of Technology Microfabricated neural probes and methods of making same
US8857275B2 (en) 2011-05-02 2014-10-14 California Institute Of Technology NEMS sensors for cell force application and measurement
US10156585B2 (en) 2003-03-11 2018-12-18 Board Of Regents Of The Nevada System Of Higher Education, On Behalf Of The University Of Nevada, Reno Cantilevered probes having piezoelectric layer, treated section, and resistive heater, and method of use for chemical detection
CN113091993A (zh) * 2021-03-23 2021-07-09 北京航空航天大学 一种多级悬臂梁结构及其仿生压差传感器

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JP4540065B2 (ja) * 2005-10-25 2010-09-08 セイコーインスツル株式会社 微小力測定装置及び生体分子観察方法
CN111609870B (zh) * 2015-01-29 2022-04-01 万渡江 一种微电子机械系统传感器的大规模生产方法
DE102019204464A1 (de) * 2019-03-29 2020-10-01 Airbus Operations Gmbh Rauch- und brandherddetektionssystem, brandschutzsystem für flugzeuge und verfahren zur detektion von rauch und brandherden

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US6559474B1 (en) * 2000-09-18 2003-05-06 Cornell Research Foundation, Inc, Method for topographical patterning of materials

Cited By (28)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10156585B2 (en) 2003-03-11 2018-12-18 Board Of Regents Of The Nevada System Of Higher Education, On Behalf Of The University Of Nevada, Reno Cantilevered probes having piezoelectric layer, treated section, and resistive heater, and method of use for chemical detection
US7434476B2 (en) 2003-05-07 2008-10-14 Califronia Institute Of Technology Metallic thin film piezoresistive transduction in micromechanical and nanomechanical devices and its application in self-sensing SPM probes
US7302856B2 (en) 2003-05-07 2007-12-04 California Institute Of Technology Strain sensors based on nanowire piezoresistor wires and arrays
US7552645B2 (en) 2003-05-07 2009-06-30 California Institute Of Technology Detection of resonator motion using piezoresistive signal downmixing
US7617736B2 (en) 2003-05-07 2009-11-17 California Institute Of Technology Metallic thin film piezoresistive transduction in micromechanical and nanomechanical devices and its application in self-sensing SPM probes
US8524501B2 (en) 2003-10-17 2013-09-03 Board Of Regents Of The Nevada System Of Higher Education Self-sensing array of microcantilevers for chemical detection
GB2432001B (en) * 2003-10-17 2009-04-15 Nevada System Of Higher Education Self-sensing array of microcantilevers for chemical detection
US7762719B2 (en) 2004-04-20 2010-07-27 California Institute Of Technology Microscale calorimeter
US8750957B2 (en) 2004-06-01 2014-06-10 California Institute Of Technology Microfabricated neural probes and methods of making same
US8434161B1 (en) 2004-10-01 2013-04-30 Board Of Regents Of The Nevada System Of Higher Education, On Behalf Of The University Of Nevada Cantilevered probe detector with piezoelectric element
US8434160B1 (en) 2004-10-01 2013-04-30 Board Of Regents Of The Nevada System Of Higher Education, On Behalf Of The University Of Nevada Cantilevered probe detector with piezoelectric element
US10473636B2 (en) 2004-10-01 2019-11-12 Board Of Regents Of The Nevada System Of Higher Education, On Behalf Of The University Of Nevada Cantilevered probe detector with piezoelectric element
US8713711B2 (en) 2004-10-01 2014-04-29 Board Of Regents Of The Nevada System Of Higher Education, On Behalf Of The University Of Nevada Cantilevered probe detector with piezoelectric element
US7694346B2 (en) 2004-10-01 2010-04-06 Board Of Regents Of The Nevada System Of Higher Education On Behalf Of The University Of Nevada Cantilevered probe detector with piezoelectric element
US7409851B2 (en) * 2005-03-29 2008-08-12 Cornell Research Foundation, Inc. Detection of small bound mass
US7408147B2 (en) 2005-07-27 2008-08-05 Wisconsin Alumni Research Foundation Nanoelectromechanical and microelectromechanical sensors and analyzers
WO2008091294A2 (fr) * 2006-07-28 2008-07-31 California Institute Of Technology Système nanoélectromécanique polymère pour la physiologie cellulaire et système de positionnement de cellules microfabriquées pour micro-biocalorimètre
US7966898B2 (en) 2006-07-28 2011-06-28 California Institute Of Technology Polymer NEMS for cell physiology and microfabricated cell positioning system for micro-biocalorimeter
WO2008091294A3 (fr) * 2006-07-28 2009-01-29 California Inst Of Techn Système nanoélectromécanique polymère pour la physiologie cellulaire et système de positionnement de cellules microfabriquées pour micro-biocalorimètre
US8827548B2 (en) 2006-07-28 2014-09-09 California Institute Of Technology Polymer NEMs for cell physiology and microfabricated cell positioning system for micro-biocalorimeter
US7884324B2 (en) 2007-06-03 2011-02-08 Wisconsin Alumni Research Foundation Nanopillar arrays for electron emission
US8742333B2 (en) 2010-09-17 2014-06-03 Wisconsin Alumni Research Foundation Method to perform beam-type collision-activated dissociation in the pre-existing ion injection pathway of a mass spectrometer
US9053916B2 (en) 2010-09-17 2015-06-09 Wisconsin Alumni Research Foundation Method to perform beam-type collision-activated dissociation in the pre-existing ion injection pathway of a mass spectrometer
US9478405B2 (en) 2010-09-17 2016-10-25 Wisconsin Alumni Research Foundation Method to perform beam-type collision-activated dissociation in the pre-existing ion injection pathway of a mass spectrometer
US8857275B2 (en) 2011-05-02 2014-10-14 California Institute Of Technology NEMS sensors for cell force application and measurement
US8507845B2 (en) 2011-06-02 2013-08-13 Wisconsin Alumni Research Foundation Membrane detector for time-of-flight mass spectrometry
CN113091993A (zh) * 2021-03-23 2021-07-09 北京航空航天大学 一种多级悬臂梁结构及其仿生压差传感器
CN113091993B (zh) * 2021-03-23 2022-05-17 北京航空航天大学 一种多级悬臂梁结构及其仿生压差传感器

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JP2006512564A (ja) 2006-04-13
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WO2003095616A3 (fr) 2004-04-29
CN1663014A (zh) 2005-08-31

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