Nanoscale adhesion, friction and wear studies of biomolecules on silicon based surfaces

Nanoscale adhesion, friction and wear studies of biomolecules on silane polymer-coated silica and alumina-based surfaces

“…APTES interfaces are multilayered due to intermolecular polymerization, with significant cross-linking between polymer monomers but sparse cross links between polymer and substrate. AFM data suggest that this is true of our interfaces (Bhushan et al , 2006aLee et al 2005;Eteshola et al 2008).…”

“…We used 3-aminopropyltriethoxysilane (APTES) on MOSFET interfaces, and have also used APTES in functional HFET protein sensors (Bhushan et al , 2006a; Lee et al 2005;Shapiro et al 2007;Eteshola et al 2008;Gupta et al 2008). APTES layers are commonly described as self-assembled monolayers (SAMs), though this is often inaccurate (Kallury et al 1994; figure 2).…”

“…Protein receptors for sensors are deployed on surfaces by direct adsorption or by conjugation to an interfacial polymer layer (Bhushan et al , 2006a; Lee et al 2005;Shapiro et al 2007;Eteshola et al 2008;Gupta et al 2008), and proteins deposited by different methods have different wear properties. Deeper understanding of nanoscale adhesion, friction and wear of biomolecular interfaces supports rational changes in interfaces, improving sensor (and other BioMEMs) function in vivo, over time.…”

Theory, fabrication and applications of microfluidic and nanofluidic biosensors

“…In other electrically based techniques, a surface-based reaction corresponds to a change in a measured electrical signal such as current [20][21][22][23], resistance [24][25][26], capacitance [27] or conductance [28][29][30][31][32][33][34] of the test sample. In addition, detection methods could also rely on mechanical changes induced owing to adsorption of target molecules or analytes to cantilevers [35][36][37] or nanowires [33], changes to inherent biomolecular charge in the case of field-effect transistors, sometimes also classified as microarray-type biosensors [38][39][40][41][42][43], or electrochemical changes such as those arising from redox reactions inducing variations in current flow [44,45]. Therefore, biosensors form a complex area of research given the diversity of target molecules, need for low false positives and variety of detection platforms available [46][47][48][49][50] with a brief summary presented in table 1a.…”

“…The solvents are usually aqueous solutions to preserve the natural state, or after processing may be organic materials. The sensor should be able to perform the [35][36][37] nanowires change in surface charge through protonation/deprotonation [33] electrical field-effect transistors changes in inherent biomolecular charge [38,[41][42][43]51] nanowires changes in electrical signal such as current, resistance, capacitance or conductance [24][25][26][27][28][29][30][31][32][33][34] optical fluorescence intensity of fluorescent signal [3][4][5] optical cavity resonator shift in resonance wavelength proportional to change in mass [7,9] surface-plasmon resonance shift in refractive index [10,11,[13][14][15][16]52] (b) sample manipulation method underlying principle involved references pumps electrokinetic pumping (including electro-osmosis) valves surface modification [53] droplets transfer electrically controlled surface tension drives liquid droplets [54,55] arrays/mixing of fluids use of heterogeneous surfaces (e.g. use of nanoholes or modified surfaces) [56,57] a As discussed in the text, many of the mechanisms can be combined with sample manipulation techniques in table 1b in microfluidic or nanofluidic platforms or can be used as stand-alone methods.…”