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We developed streaming potential/current measurement system for investigation of liquid property in 101-103 nm space (extended-nano space) [1].Using streaming potential/current system,higher electric conductivity and lower dielectric constant were quantitatively obtained in extended-nano space by regarding liquids in the channel as electric circuit.These results will be important for clarification of liquid chemistry in extended-nano space.Recently,extended-nano space has attracted much attention for biochemical analysis,drug delivery,protein and DNA folding,and sequencing or synthesis of nucleic acids in the field of nanofluidics.In this space,liquid chemistry is based on electric double layer theory.However,there are few reports of direct and quantitative measurements of liquid property due to lack of measurement methods.On the other hand,we have reported that liquids confined in this space have anomalous properties,and proposed proton transfer phase model which water molecules were loosely coupled within 50 nm from the surface with high proton mobility [2,3].In order to clarify liquid chemistry in extended-nano space,methods for evaluation of liquid property are strongly needed.In this study,we developed streaming potential/current measurement system for investigation of liquid property.Also,we quantitatively evaluated electrical conductivity and dielectric constant in extended-nano space by regarding liquids in the channel as electric circuit.Experimental setup was shown in Figure 1.Extended-nano channels were fabricated on the synthetic quartz glass plate by electron beam lithography and plasma etching.Water was filled in a chip and controlled by a pressure controller.The streaming potential/current was detected by Ag-AgCl electrodes.The concept of considering liquid flow in the channel as electric circuit was shown in Figure 2.Based on size control,flow control,electric control,electrical conductivity and dielectric constant can be evaluated directly and quantitatively from the resistance and capacitance.Results were shown in Figure 3 and 4.Higher conductivity and lower dielectric constant were obtained in extended-nano space compared to that of microspace.Higher conductivity was considered to be contribution of higher proton mobility.Lower dielectric constant suggested that water molecules were loosely coupled.These results agreed with proposed proton transfer phase model based on our previous results of liquid properties.Also,conductivity and dielectric constant are important parameter in electric double layer theory.With numerical discussion based on electric double layer theory,clarification of liquid chemistry in extended-nano space is expected,and it will be important information as basic science in nanofluidics.