Abstract:
The present invention relates to methods and devices for extraction of bodily fluids from tissue by creating microscopic openings in the outermost layers of the skin and drawing out the fluid. One embodiment of the invention is a cylindrical hollow member, made of electrically conducting material, with sharpened edges.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation-in-part of commonly owned, copending U.S. application Ser. No. 14/983,759, filed Dec. 30, 2015, the disclosure of which is hereby incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to a device and methods of using the same for extracting small volumes of fluids from tissues by creating microscopic openings in the outermost layers of the skin and subsequently drawing out the fluid. 
       BACKGROUND OF THE INVENTION 
       [0003]    Recent developments in technology have enabled simultaneous testing of a variety of health conditions from a single or a few drops of blood. In addition, new areas of testing are envisioned that would facilitate the testing of patient suitability for a new drug or identify gene sequences that indicate the presence of cancer or infection. 
         [0004]    Blood glucose measurement is the most widely used test that requires a drop of blood. Such measurements still rely on the piercing of skin by a lancet, squeezing the skin to produce a blood drop, and aligning a glucose test strip to the blood drop. Several such painful procedures are required per day for some patients. Repeated sampling over a long time causes calluses and scarring. In addition, alignment of the small capillary in a glucose strip to the blood drop is challenging for patients with failing vision or compromised mobility. 
         [0005]    Current blood glucose measurement techniques involve drawing a drop of blood out by puncturing the skin, and collecting the blood into a chamber inside a glucose strip. The blood then reacts with an enzyme called glucose oxidase which produces an electrical or optical change that is sensed and displayed as a blood glucose level by the electronics inside the glucose meter into which the glucose strip is plugged. 
         [0006]    U.S. Pat. No. 8,241,229 describes a drill device known as the PathFormer, and a method of removing the stratum corneum from the epidermis to permit blood collection from the body for analysis, which comprises the steps of drilling into a target area with a drilling assembly, monitoring an electrical impedance of the target area, stopping the drilling into the target area when a change in the electrical impedance is detected, thereby forming a microconduit, and removing blood from the body through the microconduit; wherein the drilling assembly includes a motor, an impedance sensor, and a cutter, and wherein the drilling into the tissue is stopped and automatically reversed by a control module when a change in the electrical impedance of the target area is detected by the sensor. This patent is hereby incorporated herein by reference in its entirety. 
         [0007]    Human skin serves to protect the inner body from the outer world. The outermost protective shield of the skin is called the stratum corneum (SC). SC consists of 15 to 20 dead skin cells stacked atop one another, not dissimilar to the stacking of bricks used to form a wall. The thickness of the SC is approximately 4 thousandths of an inch, roughly the thickness of a sheet of paper. The SC is continuously regenerating, shredding its outermost cells and adding newly dead cells at its base from the underlying living cells protecting themselves and all internal tissues within the body. 
         [0008]    The SC is highly resistant to the flow of current, in contrast to the much lower resistance and greater conductivity of the live tissue and fluids lying immediately below the SC. By rough analogy, the SC can be considered the rubber insulation surrounding an electrical cord, with that which lies beneath the SC considered as the conductive copper wire, thus protected. The SC has much higher electrical impedance (approximately 2 million ohms) than the underlying tissue (around 20,000 ohms). 
         [0009]    The PathFormer technology is predicated on the differential in resistance between the SC and the protected tissues and fluids beneath. This allows the PathFormer device to penetrate and remove the very thin layer of SC without coming into contact with the nerve bed of the underlying live tissue. The device can be programmed to cut, drill or abrade the SC, while continuously measuring impedance. Once the SC is breached, the dramatic change in measured impedance causes the cutting member to retract automatically and immediately. Accordingly, the patient experiences no pain and there is no damage to the living tissues beneath the SC. 
         [0010]    Removal of the SC allows for safe, quick and painless delivery of several therapeutic and cosmetic agents and treatments including topical drug delivery of large molecule drugs; rapid delivery of topical anesthetic agents in neonates; treatment of psoriasis; enhanced biometric readings; hair implantation; precision bone drilling and other applications. 
         [0011]    The human nail plate is substantially equivalent to the SC and is likewise electrically resistant. Accordingly, the PathFormer device may be programmed to drill microconduits through the nail without the patient experiencing any pain. These microconduits allow true topical delivery of antifungal to treat onychomycosis (nail fungus) and nail psoriasis. A limited clinical trial in a major Boston hospital has proven the efficacy of such treatment. The device can also be used to relieve subungual hematoma (a black toe); an injury commonly suffered by athletes, soldiers, and construction workers. The PathFormer device has obtained FDA 510(k) clearance for such use. 
         [0012]    U.S. Patent Pub. No. 2009-0221893 describes a blood glucose measuring device, equipped with a drill device, attachment assembly, and disposable sensing and measurement assembly. The attachment assembly contains an attachment ring that connects to the drill device and is used to hold the disposable sensing and measurement assembly. A detach actuating cam and output shaft are attached to the drill device. Spring tongs are attached to the output shaft by a compression ring further clamp to an end cap. A skin penetrator is attached to the end cap. The disposable sensing and measurement assembly is enclosed in a disposable case. An outer telescoping anti-bend tube is attached to the end cap. An inner anti-bend capillary sensor tube contains analyte sensors and is attached to the disposable case. The electrical conductors for the analyte sensor electrodes are attached to the capillary sensor tube and thus to the disposable case. An impedance sensing electrode on the bottom of the case provides electrical contacts to the skin. The electrical conductor to the impedance sensing electrode is attached to the bottom of the disposable case. This publication is hereby incorporated herein by reference in its entirety. 
         [0013]    It is an object of the present invention to provide a device and method that enables blood sampling and analyte measurement in a single procedure. It is an object of the present invention to provide a device and method that reduces or wholly overcomes some or all of the difficulties inherent in prior known devices and methods. Particular objects and advantages of the invention will be apparent to those skilled in the art, that is, those who are knowledgeable or experienced in this field of technology, in view of the following disclosure of the invention and detailed description of certain preferred embodiments. 
       SUMMARY OF THE INVENTION 
       [0014]    The present invention relates to methods and devices for extraction of bodily fluids from tissue by creating microscopic openings in the outermost layers of the skin (stratum corneum and epidermis) and drawing out internal bodily fluids such as blood and interstitial fluid. 
         [0015]    One embodiment of the invention is a sampling and measurement unit comprising an electrically conducting element (cutter) that breaches the stratum corneum and/or the epidermis of the skin, a drive assembly that moves the cutting element repeatedly into and away from the skin, an analyte sensing element, and an electronic control module for controlling the skin cutting element and determining the quantities of one or more analytes in blood. 
         [0016]    Another embodiment is a method of extracting bodily fluids, such as and not limited to, blood and interstitial fluid from tissue, which comprises of repeating the following steps: the rotating cutter element is driven toward the skin in a ‘dither’ mode wherein the cutter is moved in small steps toward and away from the skin with a small bias in movement toward the skin, monitoring an electrical impedance, and reversing the direction of movement when a preset level of decrease in the electrical impedance is detected; the procedure is repeated until a predetermined quantity of bodily fluid is collected. 
         [0017]    As described above, one aspect of the invention is to move the cutter toward the skin in a ‘dither’ mode. When a bodily fluid emerges from the skin, the cutter draws it out using the surface tension between the fluid and the cutter. As the cutter moves toward the skin, it encounters the fluid, electrical impedance drops, and the cutter retracts (moves away from the skin). This causes the cutter to pull the fluid bolus up, thus enlarging the bolus. 
         [0018]    One embodiment of the invention is to position the analyte sensing element close to the cutter such that when the fluid is drawn out of the skin, it enters a capillary in the sensing element. This enables the unification of sampling and measurement aspects into a single device. 
         [0019]    Another aspect of the invention is to roughen the surface of the cutter to enhance the surface tension effect and improve the extraction of the bodily fluid. 
         [0020]    One embodiment of the invention is to have the cutter spinning as it moves towards and away from the skin. The rotating cutter will create an opening in skin large enough to produce a drop of blood or interstitial fluid, and subsequently, draw the blood or interstitial drop out by surface tension. 
         [0021]    Another aspect of the invention is to have the cutter spinning until an opening is created in the skin, and subsequently, move toward and away from the skin (dither) to draw the blood or interstitial fluid out by surface tension. 
         [0022]    Another aspect of the invention is to have the cutter spinning until an opening is created in the skin, and subsequently, stop the cutter from rotating and move it toward and away from the skin (dither) to draw the blood or interstitial fluid out by surface tension. 
         [0023]    Another aspect of the invention is to have a hollow rotating cutter that will dither towards the skin to create an opening and subsequently dither to collect the fluid into the bore of the cutter wherein the fluid contacts the sensing material. 
         [0024]    As an alternative to the use of a detected change of impedance to control the cutter penetration into the skin tissue, the control unit can be modified to permit the cutter to rotate, thereby creating an opening in the skin by going into the skin until a pre-set electrical impedance is sensed. Optionally, the cutter can be allowed to move further into the skin tissue, e.g., for a predetermined distance, before retracting. 
         [0025]    Yet another embodiment of this invention is an integrated blood glucose measurement device, combining the drilling unit, the hollow rotating and dithering cutter, and conventional glucose monitoring technology, thereby providing the user with a one hand unit to monitor blood glucose. 
         [0026]    One such embodiment is a blood glucose measurement device for single handed use, comprising: 
         [0027]    a body having first and second ends and an electrically conducting surface which serves as the counterelectrode for impedance measurement; 
         [0028]    a drilling device with a cutter disposed at one end of the body, wherein the cutter is an electrically conducting element which plugs into an electrically conducting receptacle in the device, and wherein the cutter initially rotates to create a breach in skin tissue selected from the stratum corneum and the epidermis; 
         [0029]    a drive assembly disposed inside the body that, after the breach is created in the skin tissue, moves the cutting element in a dithering manner, repeatedly into and away from the skin thereby withdrawing fluid from the breach in the tissue; 
         [0030]    a test strip port for positioning a test strip adjacent to the cutter for collection of body fluid from the breach of the skin tissue; 
         [0031]    an electronic control module disposed inside the body for controlling the skin cutting element such that the dithering motion stops once adequate fluid has been collected for the test strip; 
         [0032]    measurement means for determining blood glucose in the body fluid collected by the test strip; and a readout display for the blood glucose level, disposed on the surface of the body. 
         [0033]    Another one hand blood glucose device is shown in U.S. Pat. No. 8,357,107, the disclosure of which is hereby incorporated herein by reference. 
         [0034]    Yet another embodiment of the present invention may be used for blood-based “point-of-care testing” (POCT), which has been defined as medical diagnostic testing at or near the point of care—that is, at the time and place of patient care. 
         [0035]    POCT includes for example, blood glucose testing, blood gas and electrolytes analysis, rapid coagulation testing (PT/INR, Alere, Microvisk Ltd), rapid cardiac markers diagnostics (TRIAGE, Alere), drugs, including drugs of abuse screening, pregnancy testing, food pathogens screening, hemoglobin diagnostics (HemoCue), infectious disease testing and cholesterol screening. Suitable well-known analysis components, such as lab-on-a-chip (LOC) measurement devices, may be employed in the unit, thereby integrating a number of analytical functions to achieve desired multi-screening of analytes present in the sampled blood or serum. 
         [0036]    One such embodiment is a body fluid testing device for single handed use, comprising: 
         [0037]    a device body having first and second ends and an electrically conducting surface which serves as the counterelectrode for impedance measurement; 
         [0038]    a drilling device with a cutter disposed at one end of the body, wherein the cutter is an electrically conducting element which plugs into an electrically conducting receptacle in the device, and wherein the cutter initially rotates to create a breach in skin tissue selected from the stratum corneum and the epidermis; 
         [0039]    a drive assembly disposed inside the body that, after the breach is created in the skin tissue, moves the cutting element in a dithering manner, repeatedly into and away from the skin thereby withdrawing fluid from the breach in the tissue; 
         [0040]    a test strip port for positioning a test strip adjacent to the cutter for collection of body fluid from the breach of the skin tissue; 
         [0041]    an electronic control module disposed inside the body for controlling the skin cutting element such that the dithering motion stops once adequate fluid has been collected for the test strip; 
         [0042]    measurement means for determining components in the body fluid collected by the test strip; and a readout display for the body fluid components, disposed on the surface of the device body. 
         [0043]    It should be appreciated by those persons having ordinary skill in the art(s) to which the present invention relates that any of the features described herein in respect of any particular aspect and/or embodiment of the present invention can be combined with one or more of any of the other features of any other aspects and/or embodiments of the present invention described herein, with modifications as appropriate to ensure compatibility of the combinations. Such combinations are considered to be part of the present invention contemplated by this disclosure. 
         [0044]    It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0045]      FIG. 1  is a schematic of a preferred embodiment of the invention: a cutter  2  in proximity to skin  1 . The cutter is driven toward/away from the skin by an up/down drive mechanism. The cutter may be rotated throughout all or part of the process by the rotational drive mechanism. The impedance sensor continually measures the electrical impedance between the cutter  2  and the counterelectrode  3 . The electronic control module controls the rotational and translational movement of the cutter. Once a fluid sample is collected, the analyte measurement module determines the concentration of one or more analytes in the fluid. The concentrations of the analytes are displayed by the display module. 
           [0046]      FIG. 2  is a schematic of a preferred embodiment of the blood sampling process. The cutter is driven toward the skin in dither mode (Panel  1 ). When the skin breaches the stratum corneum of the skin, it encounters the low electrical impedance of the epidermal tissue (Panel  2 ); it retracts from the skin leaving an opening in the stratum corneum (Panel  3 ). As the cutter pulls out, interstitial fluid appears out of the opening (Panel  4 ). As the cutter drives down toward the skin, interstitial fluid/blood flows out of the skin, when the fluid contacts the cutter, a low impedance is sensed causing the cutter to retract (Panel  5 ). During the retraction, surface tension forces enable the cutter to drag the bolus out, enlarging it (Panel  6 ). 
           [0047]      FIG. 3  shows the setup to demonstrate the proof-of-concept of the invention. The device  1  is placed on the back of hand (as an example site). The device  1  has two motors,  3  to drive the cutter  12  toward and away from the skin  18  and  4  to rotate the cutter around its long axis. A lead screw mechanism  8  is used to drive the movable carriage  6 . The foot of the device  13  has a foot ring  14  with a central opening that enables the skin to bulge in toward the cutter to create a firm surface for the cutter to contact. An electrically conducting ring  15  is used as a counterelectrode. In certain embodiments a pair of ECG electrodes placed over the skin serves as the counterelectrode. A glucose sensing strip  16  is inserted into the foot ring  14 , and the other end of the strip is inserted into a glucose meter  17 . A cutter  12  is shown as a hollow tube that tapers near the tip to form a sharp cutting edge (such as a sharpened, even bottomed small hypodermic tubing stock). 
           [0048]      FIG. 4  shows the sampling of interstitial fluid using an embodiment of the invention. Successive panels show the intact skin, appearance of interstitial fluid, fluid bolus contacting the cutter, and the lifting of the bolus by the tip of the cutter thus enlarging the bolus. 
           [0049]      FIG. 5  shows the sampling of blood using an embodiment of the invention. Successive panels show the intact skin, appearance of blood, blood bolus contacting the cutter, and the lifting of the bolus by the tip of the cutter thus enlarging the bolus. 
           [0050]      FIG. 6  shows measurement of blood glucose using interstitial fluid. The glucose strip is placed horizontally on the skin with the capillary opening located close to the cutter (left). As the interstitial fluid emerges from the skin, it is taken up by the capillary tube in the glucose strip (right). 
           [0051]      FIG. 7  shows an alternate arrangement of the glucose strip, the strip is now placed vertically with the capillary in the strip contacting the skin (left). As the blood bolus appears from the skin, it is absorbed into the capillary tube (right). 
           [0052]      FIGS. 8-11  illustrate a proposed commercial embodiment of an integrated unit, combining the drilling unit, the hollow rotating and dithering cutter, and conventional glucose monitoring technology, in a one hand blood glucose device. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0053]    The fluid collection method presented here results from the interaction of different forces acting on a volume of blood that appears from the opening made in the skin. The liquid contracts its surface area to maintain the lowest surface energy, causing it take a spherical shape. But, skin is not a flat, homogeneous surface; the uneven surface of the skin causes the blood drop to spread to a non-spherical shape. The surface tension of the blood drop determines its shape. A liquid drop (blood in this case) resting on a solid surface (skin) forms an angle called a contact angle between the liquid-solid interface and the liquid-vapor (air) interface. When a solid, such as a cutter, is immersed or pulled out of the blood drop, an advancing or receding contact angle is established. As the cutter is withdrawn from the blood, it imposes a force on the blood molecules, drawing them out along with the cutter. This, in turn, expands the volume of the blood bolus. The height to which the cutter deforms the blood drop depends on the wettability of the cutter (material make-up of the cutter), diameter of the cutter and the speed of retraction. 
         [0054]      FIGS. 1-7  provide details regarding experiments performed using the apparatus and techniques described therein. These experiments are but a few of the possible applications and should not be viewed as a compressive list or discussion. The experiments were conducted with the setup shown in  FIG. 3 . The device  1  was placed on the back of hand (as an example site). The device  1  has two motors,  3  to drive the cutter  12  toward and away from the skin  18  and  4  to rotate the cutter around its long axis. A lead screw mechanism  8  is used to drive the movable carriage  6 . The foot of the device  10  has a foot ring  14  that contacts the skin. An electrically conducting ring  15  is used as a counterelectrode. In certain embodiments a pair of ECG electrodes contacting skin  18  served as the counterelectrode. A glucose sensing strip  16  is inserted into the foot ring  14 , and the other end of the strip is inserted into a conventional glucose meter  17 . 
       EXAMPLES 
       [0055]    The following non-limiting examples serve to illustrate certain embodiments of the invention but are not to be construed as limiting. Variations and additional or alternative embodiments will be readily apparent to the skilled artisan on the basis of the disclosure provided herein. 
       Example 1 
     Sampling of Interstitial Fluid 
       [0056]    A 0.014″ diameter cutter with a short flute (0.015″ long) was mounted in a PathFormer device ( 1  of  FIG. 3 ). The device uses skin impedance as a trigger to limit the depth of penetration into the skin. The device was used in the ‘dither’ mode in this experiment. A pair of Norotrode 20 electrodes stuck on the skin (away from the site of drilling) was used as counterelectrodes. The device was set to 15 k□ trigger resistance. After the 10th dither, clear interstitial fluid emerged from the skin. At 30 th  dither, there was a slight pricking sensation at which point a large bolus of interstitial fluid appeared ( FIG. 4 ). Subsequently, the cutter started moving slowly into the bolus and drawing the fluid out. When the device was turned off and lifted off the skin, blood appeared from the site mixing with the bolus of interstitial fluid. 
       Example 2 
     Sampling of Blood 
       [0057]    A 0.014″ diameter endmill was used as the cutter. The device was set to 15 k□ trigger resistance. After 10 dithers, blood appeared via the opening, but the cutter did not appear to touch the skin during subsequent dithering ( FIG. 5 ). The hole was clean and circular, but skin fragments were stuck to the cutter. 
       Example3 
     Sharpened Stainless Tube as Cutter 
       [0058]    A stainless steel needle tube with its ends sharpened was used as the cutter ( FIG. 5 ). The outside diameter of the tube was 0.024″. The tube was epoxied to a cylindrical brass holder with a 0.025″ hole through it. The back end of the tube was left open. The standard dither protocol was used: dither down into the skin until the preset trigger impedance (15 kΩ in this case) was reached, then retract and repeat the dither process. Within the first two dithers, blood started appearing, the cutter kept retracting, reaching down to the top of the blood bolus, pulling the bolus up, the contact between the bolus and the cutter breaks, the cutter goes down again. There was no sensation during the procedure. There was an ample bolus of blood at the end of the experiment (around 30 dithers). The cutter was clean on the inside, but there was a blood stain around the outside surface close to the end. 
       Example 4 
     Abraded Cutter 
       [0059]    A solid with a rough surface has a higher wettability than a smooth cutter. So, a 0.020″ diameter endmill was abraded by directing a stream of high speed aluminum oxide powder on it. The cutter cut into the skin on the first dither producing a bolus of blood. The bolus continued to increase in size over the next 10 dithers. The cutter subsequently reached the tip of the bolus and pulled back on every dither. 
       Example 5 
     Integrated Blood Sampling and Blood Glucose Measurement—Vertically Aligned Strip 
       [0060]    A 0.024″ diameter flat bottomed endmill was used as the cutter. A glucose strip was located close to the cutter by placing it vertically into a slot in the foot ring ( FIG. 7 ). The glucose sensing strip was inserted into the glucose meter just before the drilling commenced. The device was operated in the dither mode with the retraction on low impedance being longer than the downward travel. Interstitial fluid started flowing out after the 4 th  dither. The cutter started drawing the fluid out with every subsequent dither. 
         [0061]    The glucose strip was located away from the bolus, so the strip was moved closer to the bolus by the 23 rd  dither; it took 10 more dithers to get enough fluid into the meter. The meter read 115 mg/dL at the end of the procedure. The cutter looked clean and sharp (although a bit more shiny) after drilling. 
       Example 6 
     Integrated Blood Sampling and Blood Glucose Measurement—Horizontally Aligned Strip 
       [0062]    A stainless steel needle (23 gauge) with the end sharpened by abrading the outside and inside surface of the needle end was used ( FIG. 6 ). The outside diameter of the needle was 0.024″. The needle was epoxied to a cylindrical brass holder with a 0.025″ hole through it. The back end of the needle was left open. The standard dither protocol was used: dither down into the skin until the preset trigger impedance (15 k□ in this case) was reached, then retract and repeat the dither process. But, the drill stopped spinning after it encountered low impedance for the fifth time. A glucose strip was placed horizontally in the footer ring slot. The strip capillary tip was located very close to the needle cutter. There was very little blood from the dithering process. After around 1 minute, the strip had enough blood to make a measurement (91 mg/dL). 
       Example 7 
     One Hand Integrated Unit 
       [0063]    As illustrated in  FIGS. 8-11 , another embodiment of the present invention is directed to a proposed commercial embodiment of a one hand integrated blood glucose measurement unit, based on the concepts discussed above regarding  FIGS. 1-7 . Conventional blood glucose sensing circuitry is employed as the measurement means for the blood glucose meter. Such circuitry is well known to those skilled in the art. See, for example, U.S. Pat. No. 4,787,398, which is hereby incorporated herein by reference. 
         [0064]    As shown in  FIG. 8 , in this proposed commercial configuration, the hand held device is approximately the size and shape of an oversized white board marker. The device foot that rests against the patient&#39;s skin accepts insertion of a typical disposable blood glucose capillary strip together with a disposable piercing cutter. 
         [0065]    As shown in  FIG. 9 , the device housing is electrically conductive, and once the device has sensed the electrical impedance of the controlling hand gripping the device and the foot of the unit placed securely against the skin, a ready signal appears in the readout. The patient then presses a button on the device causing the cutter to begin spinning and advancing toward the test site. 
         [0066]    As shown in  FIG. 10 , once the cutter penetrates the dead skin cells of the stratum corneum, a great reduction in electrical impedance is detected. This change causes the cutter to stop spinning and immediately retract from the conduit created through the stratum corneum. The slight pressure of the foot of the device surrounding the test site causes interstitial fluid and blood to fill the conduit through the stratum corneum simultaneously as the cutter retracts out of the conduit. 
         [0067]    This retraction occurs before the cutter reaches and damages the underlying living tissue and the nerves. Thus, there is no sensation of pain or damage to the living epidermis tissues. Right after the first retraction, the device goes into “dither” mode, rapidly advancing and retracting, each advance is quickly halted by the drop in electrical impedance when the cutter touches the blood and the cutter is again withdrawn. 
         [0068]    Each time the cutter touches the liquid, surface tension between the cutter and liquid lifts more blood out of the conduit. As a result of the bolus building atop the opening, the cutter never reenters the patient&#39;s skin a second time. With each dither, the surface tension caused by the cutter&#39;s contact with the fluids exiting the conduit causes the bolus to continue growing until the blood comes into contact with the capillary component of the test strip. 
         [0069]    As shown in  FIG. 11 , once the test strip has collected enough blood to produce a reading, dithering stops, an audio cue sounds and the patient&#39;s blood glucose reading appears in the device display. It takes approximately five seconds from device activation to final glucose readout. The entire process is painless. The conduit through the stratum corneum heals quickly without leaving tissue damage. This blood harvesting capability may be used for other blood chemistry as well. 
         [0070]    As used herein, the singular forms “a”, “an” and “the” include plural unless the context clearly dictates otherwise. Moreover, when an amount, concentration, or other value or parameter is given as either a range, preferred range, or a list of upper preferable values and lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. Where a range of numerical values is recited herein, unless otherwise stated, the range is intended to include the endpoints thereof, and all integers and fractions within the range. It is not intended that the scope of the invention be limited to the specific values recited when defining a range. 
         [0071]    From the foregoing, it will be appreciated that although specific examples have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit or scope of this disclosure. It is therefore intended that the foregoing detailed description be regarded as illustrative rather than limiting, and that it be understood that it is the following claims, including all equivalents, that are intended to particularly point out and distinctly claim the claimed subject matter.