Closed-Loop Nanopatterning of Liquids with Dip-Pen Nanolithography

Abstract

The ability to reliably manipulate small quantities of liquids is the backbone of high-throughput chemistry, but the continual drive for miniaturization necessitates creativity in how nanoscale samples of liquids are handled. Here, we describe a closed-loop method for patterning liquid samples on pL to sub-fL scales using scanning probe lithography. Specifically, we employ tipless scanning probes and identify liquid properties that enable probe−sample transport that is readily tuned using probe withdrawal speed. Subsequently, we introduce a novel twoharmonic inertial sensing scheme for tracking the mass of liquid on the probe. Finally, this is combined with a fluid mechanicsbased iterative control scheme that selects printing conditions to meet a target feature mass to enable closed-loop patterning with better than 1% accuracy and ∼4% precision in terms of mass. Taken together, these advances address a pervasive issue in scanning probe lithography, namely, real-time closed-loop control over patterning, and position scanning probe lithography of liquids as a candidate for the robust nanoscale manipulation of liquids for advanced high-throughput chemistry.

Mechanical Consequences of Oxygen Inhibition in Vat Polymerization

“…[ 35 ] Here, we utilized a tipless AFM cantilever to capture a resin droplet and then pattern sub‐picoliter quantities of the resin while tracking the amount of resin on the probe using inertial sensing. [ 36 ] Specifically, the mass and location of the loaded resin drop were determined by measuring the frequency of the first two vibrational resonance modes in between each step of the patterning process. As shown in the schematic ( Figure a), the durable resin was first nanopatterned on a hydrophobic silicon wafer.…”

“…The mass of loaded resin on the cantilever was quantified according to the two‐mode inertial mass sensing method. [ 36 ] All the resin features were patterned with an attractive set point of 300 nN, 1 s dwell time, 1 µm s −1 approach speed, and 10 µm s −1 retraction speed. The mass of each patterned feature was determined by measuring the thermal PSD of the cantilever after each patterning force‐displacement curve.…”

“Writing biochips”: high-resolution droplet-to-droplet manufacturing of analytical platforms

“…As a result, the authors found a mass resolution limit of about 5 pg in their set-up which resulted in a resolution of about 5 fL considering a water-based ink. A breakthrough has been recently reported by Saygin and coworkers, 68 who firstly demonstrated real-time closed-loop control whilst patterning droplets with volumes on the pL to sub-fL scales reaching resolutions down to 20 aL (Fig. 1).…”

Confined Etchant Layer Technique: An Electrochemical Approach to Micro-/Nanomachining

“…These techniques are usually based on scanning probe techniques (SPM) such as scanning tunneling microscopy (STM), , atomic force microscopy (AFM), scanning electrochemical microscopy (SECM), − etc. By using the nanometer-sized tip electrodes, AFM and STM were demonstrated to fabricate metallic nanostructures, cluster arrays, or even single atom patterns on conductive substrates by electrochemical deposition. − If a micro-/nanometer-sized micropipette is adopted as the scanning tip to construct a microcell, recently EC-SPMs have been well developed as an effective electrochemical 3D-printing technique working in an ambient environment. − These are indeed direct-writing techniques and are very useful for the research of principle verification and custom-tailored fabrications. − The machining accuracy depends actually on the size of the scanning probe even if the electrochemical reaction is coupled by a mass transfer process and consequently, there exists a diffusion layer on the electrode surface. Ultrashort voltage pulses (USVP) has been introduced in 2000 to improve the machining accuracy further. , Nevertheless, EC-SPM direct-writing techniques have been suffered from the low efficiency because of the point-by-point machining mode.…”