Micro device for measuring tissue impedance

Abstract

A micro-device for measuring impedance of animal tissue by simulating alternating current with low power direct current to provide a miniaturized device that carries out electrical impedance procedures.

1 . A micro-device for the measurement of tissue impedance by electrical impedance spectroscopy technique utilizing low power direct current, said device comprising:
 a. a low voltage source of direct supply current;   b. a micro-controller operatively connected to said source of direct current by circuitry including a current supply line and a common line, said micro-controller controlling the polarity of said circuit by alternating supply current draw between the current supply line and the common line,   c. said micro-controller controllably generating positive current pulses when said supply current is drawn through said supply current line and controllably creating negative current pulses when said supply current is drawn through said common line;   d. a Kelvin-configured positive driving electrode operatively connected to said microcontroller for driving a series of positive pulse signals into a biological load when said supply current is drawn through said supply current line and a Kelvin configured negative driving electrode operatively connected to said micro-controller for driving a series of negative pulse signals into said biological load when said supply current is drawn through said common line;   e. a Kelvin-configured sensing electrode series connected to a fast analog switch and a sample storage and hold capacitor for accumulating microsamples of charge of incremental specifically timed samples of potential of said series of pulse signals through said biological load as said at least one fast acting analog switch is closed by said micro-controller,   f. at least one analog to digital converter operatively connected to said sample storage and hold capacitor for converting an accumulated charge from said storage sample and hold capacitor to digital format;   g. wireless transmission circuitry operatively connected to said micro-controller for transmitting said accumulated charge to an external receiver for computation of impedance;   whereby alternating current is simulated by injecting a series of positive and negative pulses of direct current into a biological load and sampling an incremental charge of a micro section of each pulse and accumulating said incremental charge of each pulse until maximum potential of said biological load is accumulated, thereafter converting said maximum accumulated potential to digital format and computing impedance therefrom.   
     
     
         2 . The micro-device of  claim 1  for the measurement of tissue impedance by electrical impedance spectroscopy technique wherein said micro-device is employed to simulate AC coupled, sine-wave driven, dual-phase detector EIS ‘using low power direct current. 
     
     
         3 . The micro-device of  claim 1  for the measurement of tissue impedance by electrical impedance spectroscopy technique wherein said positive driving electrode drives positive currant limited positive voltage pulses of known frequency into said biological load and said negative driving electrode drives negative voltage pulses of known frequency into said biological load. 
     
     
         4 . The micro-device of  claim 1  for the measurement of tissue impedance by electrical impedance spectroscopy technique wherein at least one resistor is provided in said currant supply line for limiting said supply current frequency. 
     
     
         5 . The micro-device of  claim 1  for the measurement of tissue impedance by electrical impedance spectroscopy technique wherein said supply current is limited by at least three resistors to a low frequency of 25 Hz, a mid-frequency of 2 KHz and a high frequency of 100 KHz, said current supply lines being operatively connected to said micro-controller for selection of said supply current frequency by said micro-controller. 
     
     
         6 . The micro-device of  claim 1  for the measurement of tissue impedance by electrical impedance spectroscopy technique wherein said positive pulse signals and said negative pulse signals are square wave form. 
     
     
         7 . The micro-device of  claim 1  for the measurement of tissue impedance by electrical impedance spectroscopy technique wherein said fast acting analog switch is closed by said micro-controller for a closure period of less than three microseconds to obtain a microsample of potential of each said pulse signal. 
     
     
         8 . The micro-device of  claim 6  for the measurement of tissue impedance by electrical impedance spectroscopy technique wherein said each said pulse of said series of pulses is sampled at precisely the same point on a wave form of each said pulse of said series. 
     
     
         9 . The micro-device of  claim 7  for the measurement of tissue impedance by electrical impedance spectroscopy technique wherein said each said pulse of said series of pulses is sampled at precisely the same time during the closure period of said fast acting analog switch. 
     
     
         10 . The micro-device of  claim 9  for the measurement of tissue impedance by electrical impedance spectroscopy technique wherein said series of pulses is sampled at 66% of said fast acting switch closure period. 
     
     
         11 . The micro-device of  claim 8  for the measurement of tissue impedance by electrical impedance spectroscopy technique wherein each pulse of said series of positive pulses is sampled at about 90° of said wave form. 
     
     
         12 . The micro-device of  claim 8  for the measurement of tissue impedance by electrical impedance spectroscopy technique wherein each pulse of said series of negative pulses is sampled at about 270° of said wave form. 
     
     
         13 . The micro-device of  claim 7  for the measurement of tissue impedance by electrical impedance spectroscopy technique wherein each pulse of said series of pulses is sampled at approximately 66% of closure period of said fast acting switch. 
     
     
         14 . The micro-device for the measurement of tissue impedance by electrical impedance spectroscopy technique of  claim 1  wherein a Kelvin-configured positive driving electrode is operatively connected to said positive pulse generator and a Kelvin-configured negative driving electrode is operatively connected to said negative pulse generator, said positive and negative pulse generators being alternately operated and two Kelvin-configured sensing electrodes are each series connected to said fast analog switch and said sample storage and hold capacitor for accumulating microsamples of charge of incremental specifically timed samples of potential of said series of positive and negative pulse signals through said biological load as said fast acting analog switch are closed by said micro-controller, 
     
     
         15 . A non-invasive, wearable bioimpedance device for screening animal tissue comprising:
 a. a low voltage battery for supplying direct current;   b. a micro-controller operatively connected to said source of direct current by circuitry including a current supply line and a common line, said micro-controller controlling the polarity of said circuit by alternating supply current between the current supply line and the common line,   c. a positive pulse generator operatively connected to and controlled by said microcontroller for creating positive pulse signals when said direct current is drawn through said current supply line and a negative pulse generator operatively connected to and controlled by said micro-controller for creating negative pulse signals when said supply current is drawn through said common line;   d. two fast acting analog switches operatively connected to said micro-controller for being opened and closed thereby,   e. a Kelvin-configured positive driving electrode operatively connected to said positive pulse generator for driving a series of positive pulse signals from said positive pulse generator into said tissue and a Kelvin-configured negative driving electrode operatively connected to said negative pulse generator for driving a series of negative pulse signals from said negative pulse generator into said tissue, said series of positive and negative pulses being alternately driven into said tissue;   f. a pair of Kelvin-configured sensing electrodes, each sensing electrode series connected to a fast analog switch and a sample storage and hold capacitor for accumulating microsamples of charge of incremental specifically timed samples of potential from each pulse signal of said series of pulse signals through said biological load as said at least one fast acting analog switch is closed by said micro-controller,   g. at least one analog to digital converter operatively connected to said sample storage and hold capacitor for converting an accumulated charge from said storage sample and hold capacitor to digital format;   h. wireless transmission circuitry operatively connected to said micro-controller for transmitting said accumulated charge to an external receiver for computation of tissue impedance; and   i. a device for securing said bioimpedance device electrodes in place while said device is being worn;   
       whereby low power direct current simulates alternating current and tissue is screened by electro impedance spectroscopy (EIS) technique.