Flow cytometery system with fluidics control system

Abstract

A system, method, and apparatus are provided for flow cytometry. In one example, the flow cytometry system includes dual laser devices and dual scatter channels to measure velocity of particles in a core stream of sample fluid. The total flow rate of the sample fluid and the sheath fluid around the sample fluid is controlled, and thus held constant, by a feedback control system controlling a vacuum pump based on differential pressure across ends of a flow channel in the flow cell.

1 - 18 . (canceled) 
     
     
         19 . An apparatus for control of a flow of particles in a flow channel of a flow cytometer, the apparatus comprising:
 a time keeping device to generate a clock signal and a digital time stamp signal;   a first register in communication with the time keeping device to store a first peak digital time stamp based on a first scatter channel detecting a first peak in light scattered by a particle flowing through a first laser beam;   a second register in communication with the time keeping device to store a second peak digital time stamp based on a second scatter channel detecting a second peak in light scattered by the particle flowing through a second laser beam; and   a digital mathematical logic device coupled to the first register and the second register to receive the first peak time stamp and the second peak time stamp associated with the particle, the digital mathematical logic device configured to determine a time difference between the first peak digital time stamp and the second peak digital time stamp;   wherein the time difference is inversely proportional to particle velocity and contributes to the generation of a feedback control signal to control a core fluid flow rate of the flow channel.   
     
     
         20 . The apparatus of  claim 19 , further comprising:
 a packetizing device coupled to the digital mathematical logic device to receive the time difference and assemble it together into a data packet with information regarding the particle.   
     
     
         21 . The apparatus of  claim 19 , wherein
 the time difference contributes to the generation of the feedback control signal to control a vacuum pump to vary a fluid rate in the flow channel to maintain a constant average time difference and a constant average particle velocity.   
     
     
         22 . The apparatus of  claim 19 , wherein
 the digital mathematical logic device is further configured to determine a particle velocity of the particle by dividing a distance in the flow channel between positions of the first laser and the second laser with the time difference.   
     
     
         23 . The apparatus of  claim 19 , wherein
 the digital mathematical logic device is further configured to store and accumulate in a storage device a plurality of time differences for particles over a period of time and determine an average time difference by summing the plurality of time differences together and dividing by the total number of particles.   
     
     
         24 . The apparatus of  claim 19 , wherein
 a storage device in communication with the digital mathematical logic device to store and accumulate a plurality of time stamp differences over a period of time;   a second digital mathematical logic device coupled to the storage device, the second digital mathematical logic device is configured to determine an average time stamp difference by summing together the plurality of time stamp differences and dividing by the total number of particles; and   wherein the average time stamp difference is the feedback control signal of the flow cytometer system to control flow rate and assure a high signal to noise ratio in particle detection by each of two side scatter channels.   
     
     
         25 . The apparatus of  claim 19 , wherein
 a storage device in communication with the digital mathematical logic device to store and accumulate a plurality of particle velocities over a period of time;   a second digital mathematical logic device coupled to the storage device, the second digital mathematical logic device is configured to determine an average particle velocity by summing together the plurality of particle velocities and dividing by the total number of particles; and   wherein the average particle velocity is a feedback control signal of a flow cytometer system to control flow rate and assure a high signal to noise ratio in particle detection by each of two side scatter channels.   
     
     
         26 . The apparatus of  claim 19 , further comprising:
 a first scatter channel including a first optical detector adjacent the flow channel to receive light scattered by the particle flowing through the first laser beam, and a first gain amplifier coupled to the first optical detector, the first gain amplifier to amplify a signal from the first optical detector and generate a first pulse signal with the first peak;   a first comparator coupled to the first gain amplifier to receive the first pulse signal, the first comparator configured to compare an amplitude in the first pulse signal with a threshold value and generate a first sample enable signal;   a first analog to digital converter (ADC) coupled to the first gain amplifier to receive the first pulse signal and coupled to the first comparator to receive the first sample enable signal, the first ADC configured to periodically capture a digital sample of amplitude of the first pulse signal with a clock signal when enabled by the first sample enable signal;   a second scatter channel including a second optical detector adjacent the flow channel to receive light scattered by the particle flowing through the second laser beam, and a second gain amplifier coupled to the second optical detector, the second gain amplifier to amplify a signal from the second optical detector and generate a second pulse signal with the second peak;   a second comparator coupled to the second gain amplifier to receive the second pulse signal, the second comparator configured to compare an amplitude in the second pulse signal with the threshold value and generate a second sample enable signal;   a second analog to digital converter (ADC) coupled to the second gain amplifier to receive the second pulse signal and coupled to the second comparator to receive the second sample enable signal, the second ADC configured to periodically capture a digital sample of amplitude of the second pulse signal with the clock signal when enabled by the second sample enable signal;   wherein one of the digital samples of amplitude periodically captured by the first ADC is a first peak amplitude associated with the first peak digital time stamp; and   wherein one of the digital samples of amplitude periodically captured by the second ADC is a second peak amplitude associated with the second peak digital time stamp.   
     
     
         27 . The apparatus of  claim 26 , further comprising:
 a first storage device coupled to the time keeping device, the first ADC, and the first register, the first dual port storage device configured to receive and store a plurality of digital time stamps respectively associated with a plurality of digital amplitude samples of the first pulse signal associated with the particle flowing through the first laser beam, the first storage device further being configured to determine a first peak amplitude in the plurality of digital amplitude samples and select an associated time stamp as the first peak digital time stamp; and   a second storage device coupled to the time keeping device, the second ADC, and the second register, the second storage device configured to receive and store a plurality of digital time stamps respectively associated with a plurality of digital amplitude samples of the second pulse signal associated with the particle flowing through the second laser beam, the second storage device further being configured to determine a second peak amplitude in the plurality of digital amplitude samples and select an associated time stamp as the second peak digital time stamp.   
     
     
         28 . A method for a flow cytometer, the method comprising:
 detecting first scattered light from a particle flowing in the flow channel through a first laser beam;   generating a first pulse signal based on the first scattered light;   determining a first maximum peak in the first pulse signal at a first peak time;   detecting second scattered light from the particle flowing in the flow channel through a second laser beam;   generating a second pulse signal based on the second scattered light;   determining a second maximum peak in the second pulse signal at a second peak time;   computing a measured time difference between the second peak time and the first peak time;   generating a control signal based on the measured time difference to control a core fluid flow rate in the flow channel.   
     
     
         29 . The method of  claim 28 , wherein
 the measured time difference is inversely proportional to particle velocity in the flow channel.   
     
     
         30 . The method of  claim 29 , wherein
 a distance between the first laser beam and the second laser beam is predetermined and particle velocity can be determined by dividing the measured time difference into the distance.   
     
     
         31 . The method of  claim 28 , wherein
 the first scattered light is detected with a first optical detector; and   the second scattered light is detected with a second optical detector.   
     
     
         32 . The method of  claim 28 , wherein the control signal is a desired pressure value and the method further comprises;
 controlling a vacuum pump to decrease pressure and increase vacuum in a vacuum chamber in response to the desired pressure being less than a measured pressure in the vacuum chamber.   
     
     
         33 . The method of  claim 28 , wherein the control signal is a desired pressure value and the method further comprises;
 controlling a vacuum pump to increase pressure and lower vacuum in a vacuum chamber in response to the desired pressure being greater than a measured pressure in the vacuum chamber.   
     
     
         34 . A control system for a flow cytometer to control a controllable gas valve, the control system comprising:
 a controllable gas valve coupled between a vacuum chamber and a flow restrictor to an open atmosphere, wherein the controllable gas valve is responsive to a valve open signal;   a differential pressure transducer coupled across ends of a flow channel, the differential pressure transducer to sense over a range of pressure levels across the flow channel and generate a differential pressure signal voltage proportional to the sensed differential pressure level;   a conditioning circuit (gain amplifier) coupled to the differential pressure transducer to reduce noise and amplify the differential pressure signal voltage;   an analog to digital converter coupled to the conditioning circuit to receive the amplified differential pressured signal voltage, the analog to digital converter to periodically convert a continuous time analog signal form of the amplified differential pressure signal voltage into a time sampled digital form of the amplified differential pressure signal voltage generating a digital differential pressure signal;   a control logic device coupled to the analog to digital converter, the control logic device including
 a pressure calculator to periodically determine a pressure level based on the digital differential pressure signal, 
 a delay loop counter coupled to the pressure calculator to periodically generate a leak bit to allow the generation of the valve open signal for the controllable gas valve while a vacuum pump coupled to the vacuum chamber is operational, and 
 a control logic to periodically generate the valve open signal for the controllable gas valve in response to the generation of the leak bit to increase pressure in the vacuum chamber and reduce differential pressure across the ends of the flow channel. 
   
     
     
         35 . The control system of  claim 34 , wherein
 the control logic further generates the valve open signal when setting up the flow cytometer (e.g., degassing, sample load and change, flushing) prior to testing a fluid sample.   
     
     
         36 . The control system of  claim 34 , wherein
 the control logic disallows the periodic generation of the valve open signal when the vacuum pump coupled to the vacuum chamber is non-operational.   
     
     
         37 . The control system of  claim 34 , further comprising:
 a driver circuit coupled between the control logic device and the controllable gas valve, the driver circuit to amplify voltage of the valve open signal to control the controllable gas valve into an open position to vent the vacuum chamber to the open atmosphere through the flow restrictor.   
     
     
         38 . A method for a flow cytometer, the method comprising:
 providing a vacuum chamber that controls the flow of fluids in a flow channel of a flow cytometer;   generating a measure of differential pressure across ends of the flow channel;   determining if the measure of differential pressure is greater than a desired level of differential pressure across the ends of the flow channel; and   temporarily avoiding the generation of an open valve control signal that increases pressure and lowers vacuum in the vacuum chamber, in response to the measured differential pressure across the ends of the flow channel being greater than the desired differential pressure.   
     
     
         39 - 46 . (canceled)