Micro blood collection device

Claim 1

A micro device for collecting blood from a blood source comprising: a blood sampler cup for receiving and holding the said blood, said cup being closed at one end and open at the other end; a removable top removably secured to and closing the open end of the said cup; a vent into the said cup; a capillary tube of substantially uniform internal diameter throughout its length projecting through the said top into the cup to convey the said blood from the blood source to the said cup, the said capillary tube being so positioned that the end of tube within the cup will be proximate to the interior surface of the side wall of the cup; whereby the blood can flow directly from the blood source through the capillary tube to the interior side wall of the cup along a contiguous path, the flow of the blood into the tube is initiated under positive capillary pressure essentially defined by the equation ##EQU5## where P c equals capillary pressure, σ is surface tension of the fluid, D is capillary tube diameter and θ is the contact angle between the fluid and the tube material, flow of blood through the tube is continued under the influence of the force of gravity such that a droplet of blood forms at the distal end of the tube experiencing the pressure 4σ/D and satisfys the relationship ##EQU6## where L is the length of the capillary tube, ρ is the fluid density, g is the acceleration due to gravity, and φ is an arbitrary angle which the capillary tube makes with the vertical, the droplet forming at the distal end adapted to engage with the interior surfaces of the cup and flow will continue in a constant manner according to the formula ##EQU7## where M is the mass flow rate and μ is the viscosity of the fluid.

Claim 13

The method of collecting blood from a blood source with a micro device having a blood cup open at one end, a top closing the open end of the cup, and a capillary tube of substantially uniform internal diameter throughout its length projecting through the top into the cup with the end of the tube within the cup being proximate to the interior surface of the side wall of the cup, comprising: providing a blood source; bringing the end of the capillary tube outside of the cup into contact with the blood source to initiate the flow of blood into the tube by capillary action in accordance with the equation ##EQU8## where P c equals capillary pressure, σ is surface tension of the fluid, D is capillary tube diameter and θ is the contact angle between the fluid and the tube material; positioning the device so that the blood will flow through the tube by gravity to form an initial droplet at the end of the tube within the cup which droplet experiencing the pressure 4σ /D and satisfys the relationship ##EQU9## where L is the length of the capillary tube, ρ is the fluid density, g is the acceleration due to gravity, and φ is an arbitrary angle which the capillary tube makes with the vertical, and which droplet will come into contact with the interior surface of the side wall of the cup and flow will continue in a constant manner according to the formula ##EQU10## where M is the mass flow rate and μ is the viscosity of the fluid; whereby blood will then flow continuously from the blood source through the tube to the interior side wall of the tube along a contiguous path.

Claim 14

The method of collecting blood from a blood source with a micro device having a blood cup open at one end, a top closing the open end of the cup, and a capillary tube of substantially uniform internal diameter throughout its length projecting through the top into the cup with the end of the tube within the cup being proximate to the interior surface of the side wall of the cup, comprising: providing a blood source; bringing the end of the capillary tube outside of the cup into contact with the blood source to initiate the flow of blood into the tube by capillary action in accordance with the equation ##EQU8## where P c equals capillary pressure, σ is surface tension of the fluid, D is capillary tube diameter and θ is the contact angle between the fluid and the tube material; positioning the device so that the blood will flow through the tube by gravity to form an initial droplet at the end of the tube within the cup which droplet experiencing the pressure 4σ /D and satisfys the relationship ##EQU9## where L is the length of the capillary tube, ρ is the fluid density, g is the acceleration due to gravity, and φ is an arbitrary angle which the capillary tube makes with the vertical, and which droplet will come into contact with the interior surface of the side wall of the cup and flow will continue in a constant manner according to the formula ##EQU10## where M is the mass flow rate and μ is the viscosity of the fluid; whereby blood will then flow continuously from the blood source through the tube to the interior side wall of the tube along a contiguous path.