High-Performance Separation of Nanoparticles with Ultrathin Porous Nanocrystalline Silicon Membranes

Abstract

Porous nanocrystalline silicon (pnc-Si) is a 15 nm thin freestanding membrane material with applications in small-scale separations, biosensors, cell culture and lab-on-a-chip devices. Pnc-Si has already been shown to exhibit high permeability to diffusing species and selectivity based on molecular size or charge. In this report we characterize properties of pnc-Si in pressurized flows. We compare results to long-standing theories for transport through short pores using actual pore distributions obtained directly from electron micrographs. Measurements are in agreement with theory over a wide range of pore sizes and porosities and at orders-of-magnitude higher than those exhibited by commercial ultrafiltration and experimental carbon nanotube membranes. We also show that pnc-Si membranes can be used in dead-end filtration to fractionate gold nanoparticles and protein size ladders with better than 5 nm resolution, insignificant sample loss, and little dilution of the filtrate. These performance characteristics, combined with scalable manufacturing, make pnc-Si filtration a straightforward solution to many nanoparticle and biological separation problems.

High-performance, low-voltage electroosmotic pumps with molecularly thin silicon nanomembranes

“…Surprisingly, we discovered that the 30-nm membranes exhibited lower stall pressures than the 15-nm membranes (Table S1), indicating that thickness was not the only variable that determined stall pressures. By characterizing the pore distributions of the two membranes, we were able to calculate a significantly higher hydraulic permeability for the 30-nm membrane (Table S2) (18). Whereas the porosities of the 15-and 30-nm membranes were similar, it has been shown that larger pores naturally form in thicker membranes due to looser geometric constraints (19).…”

“…The electric field strength (8 × 10 5 V/m) and a 15-nm-thick membrane require a transmembrane voltage of only 12 mV. Low membrane resistance compared with all other resistances in the system has been observed for diffusive transport through pnc-Si (17,18,20,22). In these studies, the ultrathin dimension of the membrane results in a transmembrane resistance to diffusion that can be neglected compared with bulk resistances.…”

“…The silicon platform enables control of freestanding membrane area (Fig. 1A) and industrial-scale manufacturing (18). Pore distributions are controlled by fabrication temperatures and ramp rates during a rapid thermal crystallization step (19).…”

“…The silicon platform also enables the integration into a number of devices and fluidics systems. Previously, pnc-Si membranes have been shown to present little resistance to the diffusion of small molecules (17,(20)(21)(22) and have high permeability to water (18) and air (23).…”

Facile synthesis of wavy carbon nanowires via activation-enabled reconstruction and their applications towards nanoparticles separation and catalysis

“…So far, the main methodologies for separation of nanoparticles include ultracentrifugation, eld ow fraction, electrophoretic, magnetic and membrane separation methods. 35,[38][39][40][41][42] We found that the as-prepared WCNWs could be fabricated into membrane to be used for separate Au nanospheres with different sizes of 10 and 50 nm from solution using the handmade setup (Fig. S7, † 5a).…”