Multiplexed resistive pulse sensor based on geometry modulation for high-throughput microparticle counting

While resistive pulse sensor (RPS) has been used to characterize the nano/micro-targets (cells, biomolecules, etc.) in biomedical research, one long standing drawback is its low throughput. Here we report a novel geometry modulation based RPS to improve the throughput without increasing the complexity of measurement electronics. The sensor consists of multiple parallel sensing channels whose geometries are uniquely designed based on 7-bit spreading sequences. Because of the unique geometry, when a particle passes a sensing channel, the voltage signal from this channel is encoded by a specific waveform. Only a DC source was applied, and only one combined signal from all sensing channels was collected. For demodulation, the maximum correlation coefficient between the combined signal and each template waveform was used to identify the passage of a particle from a specific sensing channel, and the occurring time of the passage. An iterative cancellation scheme was developed to extract the identified waveforms, by a series of subtractions of the identified waveforms with amplitudes from high to low, until the correlation coefficients between the remaining signal with all template waveforms became less than 0.4 (weak correlation). Mixtures of different-sized polystyrene particles were used to test the device. Results showed that the device is capable of accurately sizing and counting various microparticles with errors of 5.8% and 5.2% while the throughput was improved 300%. With the simple structure and measurement setup, the geometry-modulated RPS has great potential for the detection and analysis of a variety of micro/nano bio-objects.