Fabrication of polydimethylsiloxane nanofluidic chips under AFM tip-based nanomilling process

Abstract

In current research realm, polydimethylsiloxane (PDMS)-based nanofluidic devices are widely used in medical, chemical, and biological applications. In the present paper, a novel nanomilling technique (consisting of an AFM system and a piezoelectric actuator) was proposed to fabricate nanochannels (with controllable sizes) on PDMS chips, and nanochannel size was controlled by the driving voltage and frequency inputted to the piezoelectric actuator. Moreover, microchannel and nanochannel molds were respectively fabricated by UV lithography and AFM tip-based nanomilling, and finally, PDMS slabs with micro/nanochannels were obtained by transfer process. The influences of PDMS weight ratio on nanochannel size were also investigated. The bonding process of microchannel and nanochannel slabs was conducted on a homemade alignment system consisted of an optical monocular microscope and precision stages. Furthermore, the effects of nanochannel size on electrical characteristics of KCl solution (concentration of 1 mM) were analyzed. Therefore, it can be concluded that PDMS nanofluidic devices with multiple nanochannels of sub-100-nm depth can be efficiently and economically fabricated by the proposed method. Electronic supplementary material The online version of this article (10.1186/s11671-019-2962-6) contains supplementary material, which is available to authorized users.

Nanomechanical sampling of material for nanoscale mass spectrometry chemical analysis

“…Overall, the volume of the sampled material is likely to correlate directly with signal strength; however, few factors that complicate this analysis are (i) unknown tip shape and the interplay between that and the sample plasticity and hardness, along with the milled material tip adhesion, will all affect the amount of material extracted and therefore the signal strength and (ii) if the sample region is heterogeneous, it is not necessarily clear that increasing the milled volume will increase the amount of analyte that makes its way to the mass sprectrometer. Work on nanomilling of material and the correlation with depth and material removal, especially in complex materials, is as of today still an active research area and deserves more exploration [25,26].…”

Scratch on Polymer Materials Using AFM Tip-Based Approach: A Review

“…However, something defective also exists in that the fabrication efficiency needs to be improved furthermore when scratching more complex structures, and the tip wear during the scratching also cannot be neglected. A similar work was conducted by Wang et al [54], when the original stage of commercial AFM system was replaced by a piezoelectric actuator to generate rotational relative motion between the tip and the sample. In this work, nanochannels with desired dimension were obtained in an easy and controllable way, which can meet the demand of preparation of nanofluidic chips.…”

“…Nanochannel, that is, nanogroove on the nanofluidic chips, is a key component, which is usually utilized to conduct biological detection. Wang et al [54] first proposed a fabrication method for nanochannels used in nanofluidic chips by the TBN method, and the details of the preparation procedures are shown in Figure 17. They used a piezoelectric actuator on the X-Y plane to generate a vibration of the sample and the relative motion between the tip and the sample is like the traditional milling process, hence, this method is named nanomilling.…”

“…The preparation procedures of nanofluidic chip based on the TBN method: ( a1 )–( a6 ) working steps of microchannel fabrication on a polydimethylsiloxane (PDMS) chip, ( a1 ) silicon sheet used for lithography substrate, ( a2 ) spin-coating of SU8 photoresist on Si substrate, ( a3 ) exposure of the SU8 layer to ultraviolet (UV) light, ( a4 ) obtained convex microstructures, ( a5 ) PDMS coating on microchannel mould, ( a6 ) final PDMS chip with microchannels, ( b1 )–( b2 ) working steps of nanochannel fabrication on a PDMS chip, ( b1 ) AFM tip scratches on polycarbonate (PC) sheet, ( b2 ) obtained nanochannel mould after scratching, ( b3 ) A-PDMS coating on nanochannel mould, ( b4 ) A-PDMS chip with convex nanostructures, ( b5 ) regular PDMS coating on A-PDMS mould, ( b6 ) final PDMS chip with nanochannels, ( c ) PDMS nanofluidic chip after bonding [54]. …”

“…Polymer materials are widely used in the fields of the Micro/Nano-Electro-Mechanical System (MEMS/NEMS) technique, such as optical mask, flexible electronic device, nanosensor and nanofluidic due to its relative low-cost, good light transmittance and excellent biocompatibility [53,54]. Among them, the most important application of polymer film is as the resist of etching [52,55].…”