A Bio-Impedance Measurement Technique Using Biphasic Current Stimulus Excitation for Implantable Stimulators

Tech ID: 29870 / UC Case 2014-786-0


UCLA researchers from the Department of Bioengineering have developed a novel efficient, low-cost, low-power technique for measuring the bio-impedance at the electrode-tissue interface, which can be incorporated into implantable stimulators.


Knowing the bio-impedance at the electrode-tissue interface is important for safety, efficacy, and function in many biomedical applications including tissue stimulators. Measuring impedance can be used as a metric for the proximity of the electrode to the target tissue. For tissue stimulators, measuring the electrical impedance is essential to ensure an effective and safe stimulus pulse is delivered. Additionally, the impedance of the electrode-electrolyte interface is vital for preventing damage to the electrode itself during stimulation. Current methods for impedance measurement are either limited to measuring at a single frequency, or are extremely complex and expensive such as Electrochemical Impedance Spectroscopy (EIS). These methods either do not give a full equivalent circuit representation of the impedance measurement or are not appropriate in terms of expense or safety for use in tissue stimulators.


UCLA researchers have developed a novel technique to accurately and inexpensively measure the bio-impedance at the electrode-tissue interface. This technique can measure the parameters of an accurate equivalent circuit model, which allows for sophisticated predictions beyond at a single frequency. This technique also ensures charge-balance on the electrode after the measurement which ensures safety of both the electrode and target tissue. This technique is also low complexity and low cost allowing for easy integration into existing commercial tissue stimulator hardware solutions.


  • Implantable neural-stimulators for in vivo and in vitro experiments 
  • Implantable muscle-stimulators 
  • Implantable cardiac-stimulators 
  • Bio-impedance diagnostics


  • Measures bio-impedance with a full equivalent circuit model 
  • Low cost 
  • Low complexity 
  • Ensures electrode and tissue safety 
  • Easily integrated into existing tissue stimulator hardware

State Of Development

Technique has been validated.

Patent Status

Country Type Number Dated Case
United States Of America Published Application 2017010565 04/20/2017 2014-786


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  • Liu, Wentai

Other Information


Bio-impedance, impedance, neural stimulator, tissue stimulator, biphasic current, electrode

Categorized As