Digital Blockade Electrochemical Counter: from Interface-Free to Interface of Either Solid/Liquid or Liquid/Liquid

Single-entity electrochemistry (SEE) has been developing for approximately 76 years since the invention of the Coulter counter. Single-entity collisional electrochemistry (SECE), a branch of SEE, refers to micro- and nanoscale electrochemistry that measures the electrical signals of single particles that randomly collide with a polarizable solid/liquid (SL) or liquid/liquid (LL) interface. Blockade-type SECE at SL and LL are denoted as blockade SECE@SL and blockade SECE@LL, respectively. Similar to the Coulter counter, they are also based on electrical impedance as the signal source for sensing single particles. This Perspective discusses the similarities and differences, their respective features, advantages and disadvantages among these three counters. In the final outlook section, we focus on the blockade SECE@LL to explore its future development directions to align it with the application goals of the Coulter counter.