The design of thin polymer membranes filled with magnetic particles on a microstructured silicon surface

Abstract

In this paper we present the fabrication and characterization of polymer nanomembranes filled with magnetic nanoparticles and attached covalently to a periodic array of free-standing silicon walls, forming an array of micro-channels with the membrane as a cover. The width of a micro-channel of about 1.4 microm sets a characteristic lateral size and the thickness of the polymer membrane ranges between 100 and 300 nm. The membrane is made of cross-linked hydrophilic polymers possessing a Young's modulus of only a few MPa. The presence of the magnetic particles within the membrane makes the film responsive to external magnetic fields. The mechanical and magnetic properties of the membrane are characterized by bulge tests and with atomic force microscopy.

Quantitative Analysis of Human Internal Limiting Membrane Extracted from Patients with Macular Holes

“…The AFM cantilevers were functionalized using layer-by-layer self-assembly (LbL) of polyelectrolyte films with opposite charges (PAH and PSS). This approach has been used extensively for the nanoassembly of diverse devices due to its simple, water-based method and the control over the resulting layer thicknesses. − LbL has been utilized for the assembly of polymer films on substrates such as glass and silicon , and, more recently, to increase the porosity of silicon nitride cantilevers used for dip-pen nanolithography . This “bottom-up” approach has also been incorporated to implantable devices such as stents, − neural, and orthopedic implants to aid with drug delivery, enhance cell adhesion and proliferation, and induce bone growth. − This approach is ideal for the modification of the microcantilevers used in the adhesion studies as these experiments were conducted in an aqueous environment.…”

Magnetically Activated Micromixers for Separation Membranes

“…Other responsive membranes have shown promise for reducing fouling using stimuli such as pH and temperature; however, these require changes to the bulk feed to obtain a membrane response. ,,, Magnetically responsive membranes can be activated through an external stimulus; therefore characteristics of the bulk feed are unaffected. Membranes responsive to an external magnetic field have been presented before, which were created by embedding magnetic nanoparticles in a polymeric matrix to create “gating” membranes for drug delivery but not filtration. − This, however, is quite different from the novel responsive NF membranes described in this study.…”

Morphing Soft Magnetic Composites

“…The versatility and good actuation metric of Magpol make it a promising material for actuator applications, including fluid pumps,88 artificial muscles116 and other actuators 78, 117. The membrane form of Magpol has also been used in MEMS devices, in microchannels or peristaltic pumps for nanofluidic systems 71, 118. Its shape changing characteristics can be used in novel dampers and seals to tune the mechanical properties (e.g., elastic modulus) of the matrix by utilizing an external magnetic field 119…”