SEM image of a 75nm wide square pattern fabricated by SLIM processing of a dot array with 100nm pitch.

<p>SEM image of a 75nm wide square pattern fabricated by SLIM processing of a dot array with 100nm pitch.</p

A plot of the optimized squareness value, <i>n</i>, vs etch time.

<p>A plot of the optimized squareness value, <i>n</i>, vs etch time.</p

The SEM images compares a) a SLIM processed pattern and b) the same sample after heat treatment for one hour at 400 °C.

<p>The SEM images compares a) a SLIM processed pattern and b) the same sample after heat treatment for one hour at 400 °C.</p

A plot showing the influence of SLIM process time and precursor thickness on the pattern width.

<p>Each curve approaches an asymptote at approximately 183nm revealing the self-limiting etch process.</p

A plot of pattern size vs etch time for different precursor openings showing little change in the pattern size distribution.

<p>A plot of pattern size vs etch time for different precursor openings showing little change in the pattern size distribution.</p

Nickel was electrodeposited into a SLIM pattern with 80nm square opening.

<p>The SEM images show a) a 52 degree projection of the nickel pillars after removing the resist and (b) a 52 degree projection of the same sample after argon plasma treatment.</p

Diagram describing the SLIM process.

<p>The precursor is dot patterns separated by a wall of thickness a₀ and b₀. SLIM processing narrows both walls at the same rate to a thickness of a₁ and b₁. At a critical thickness the etch rate reduces significantly resulting in little change towards a₂, but b₂ continues to narrow. As b₂ approaches the critical thickness, the pattern converges to a square.</p

A plot of the measured squareness ratio vs etch time for each precursor.

<p>A plot of the measured squareness ratio vs etch time for each precursor.</p

SEM images of the original precursors (a,c,e) and after SLIM processing (b,d,f).

<p>The diameters of the circles in the precursor are: a) 100nm, c) 137nm and e) 175nm.</p

Specific Detection of Proteins Using Exceptionally Responsive Magnetic Particles

Sensitivity and specificity are among the most important parameters for viable sensor technologies based on magnetic nanoparticles. In this work, we describe synthetic routes and analytical approaches to improve both aspects. Magnetic iron oxide particles having diameters of 120, 440, and 700 nm were synthesized, and their surfaces were specifically functionalized. The larger particles showed significantly stronger magnetic signals and responses when compared to commercially available magnetic particles (Dynabeads). A force-based detection method was used to distinguish specifically bound particles (via protein interactions) and nonspecifically bound ones (e.g., via physisorption). In addition, an exchange platform, denoted as exchange-induced remnant magnetization (EXIRM), was developed and utilized to detect label-free proteins specifically. Using EXIRM, the 700 nm magnetic particles showed a 7-fold increase in detection sensitivity when compared to the markedly larger commercially available Dynabeads; furthermore, EXIRM exhibited high specificity, even in a 100-fold increase of nontargeted protein. More generally, particle size effects, reaction times, and dynamic ranges are evaluated and discussed herein