title: Real-time modulated nanoparticle separation with an ultra-large dynamic range.
abstract: Nanoparticles exhibit size-dependent properties which make size-selective purification of proteins, DNA or synthetic nanoparticles essential for bio-analytics, clinical medicine, nano-plasmonics and nano-material sciences. Current purification methods of centrifugation, column chromatography and continuous-flow techniques suffer from particle aggregation, multi-stage process, complex setups and necessary nanofabrication. These increase process costs and time, reduce efficiency and limit dynamic range. Here, we achieve an unprecedented real-time nanoparticle separation (51-1500 nm) using a large-pore (2 μm) deterministic lateral displacement (DLD) device. No external force fields or nanofabrication are required. Instead, we investigated innate long-range electrostatic influences on nanoparticles within a fluid medium at different NaCl ionic concentrations. In this study we account for the electrostatic forces beyond Debye length and showed that they cannot be assumed as negligible especially for precise nanoparticle separation methods such as DLD. Our findings have enabled us to develop a model to simultaneously quantify and modulate the electrostatic force interactions between nanoparticle and micropore. By simply controlling buffer solutions, we achieve dynamic nanoparticle size separation on a single device with a rapid response time (<20 s) and an enlarged dynamic range (>1200%), outperforming standard benchtop centrifuge systems. This novel method and model combines device simplicity, isolation precision and dynamic flexibility, opening opportunities for high-throughput applications in nano-separation for industrial and biological applications.
authors.affiliation: Singapore Institute for Neurotechnology (SINAPSE), 28 Medical Dr. #05-COR, 117456 Singapore.
authors.forename: Kerwin Kwek
authors.initials: KK
authors.lastname: Zeming
authors.affiliation: Singapore Institute for Neurotechnology (SINAPSE), 28 Medical Dr. #05-COR, 117456 Singapore and Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Traylor 701/720 Rutland Ave, Baltimore, MD 21205, USA.
authors.forename: Nitish V
authors.initials: NV
authors.lastname: Thakor
authors.affiliation: Department of Biomedical Engineering, National University of Singapore, 9 Engineering Drive 1, Block EA #03-12, 117576 Singapore. biezy@nus.edu.sg biecch@nus.edu.sg and Cellular and Molecular Bioengineering Lab, National University of Singapore, Block E3A, #07-06, 7 Engineering Drive 1, 117574 Singapore.
authors.forename: Yong
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Singapore Institute for Neurotechnology (SINAPSE), 28 Medical Dr. #05-COR, 117456 Singapore and Department of Biomedical Engineering, National University of Singapore, 9 Engineering Drive 1, Block EA #03-12, 117576 Singapore. biezy@nus.edu.sg biecch@nus.edu.sg.
authors.forename: Chia-Hung
authors.initials: CH
authors.lastname: Chen
mesh_terms: D057446:Hydrodynamics; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation; D053758:Nanoparticles / Q000737:chemistry* / Q000600:supply & distribution; D010316:Particle Size; D055672:Static Electricity; D013499:Surface Properties; D013997:Time Factors