Unconventional micro-/nanofabrication technologies for hybrid-scale lab-on-a-chip

Abstract

Micro-/nanofabrication-based lab-on-a-chip (LOC) technologies have recently been substantially advanced and have become widely used in various inter-/multidisciplinary research fields, including biological, (bio-)chemical, and biomedical fields. However, such hybrid-scale LOC devices are typically fabricated using microfabrication and nanofabrication processes in series, resulting in increased cost and time and low throughput issues. In this review, after briefly introducing the conventional micro-/nanofabrication technologies, we focus on unconventional micro-/nanofabrication technologies that allow us to produce either in situ micro-/nanoscale structures or master molds for additional replication processes to easily and conveniently create novel LOC devices with micro- or nanofluidic channel networks. In particular, microfabrication methods based on crack-assisted photolithography and carbon-microelectromechanical systems (C-MEMS) are described in detail because of their superior features from the viewpoint of the throughput, batch fabrication process, and mixed-scale channels/structures. In parallel with previously reported articles on conventional micro-/nanofabrication technologies, our review of unconventional micro-/nanofabrication technologies will provide a useful and practical fabrication guideline for future hybrid-scale LOC devices.

Engineered Living Materials-Based Sensing and Actuation

“…NEMS biosensors correlate chemical or physical binding events with the mechanical motions of devices in nanometer scales, which in turn are converted into detectable electrical or optical signals. They have small form factor, extremely high sensitivity with a detection limit down to the single molecule level (Lim et al, 2015;Ha et al, 2016). The integration of ELMsbased structures with MEMS/NEMS devices has the potential to bring breakthroughs in fully functional and miniaturized ELMs-based sensors.…”

Electrokinetic ion transport in nanofluidics and membranes with applications in bioanalysis and beyond

“…More details related to nanofluidic device fabrication technologies can be found in other review articles. [29][30][31][32]…”

Combined Effects of Zeta-potential and Temperature of Nanopores on Diffusioosmotic Ion Transport

“…8,9 Most previous studies on DO use conventional nanofabrication processes with limitations in the materials governing the zeta-potentials (ζ) of the channel surfaces, throughput, dimensions, and the number of nanopores/nanochannels. 10,11 This hindered DO investigation because the governing parameters could not be varied easily. Typically, electric signals are measured along a single nanochannel, which limits the quantification accuracy because of the low transport flux.…”

“…Diffusioosmosis (DO) has attracted much attention in nanofluidic science − as a transport phenomenon universally occurring in nanopores and nanofluidic channels with surface charges under electrolyte gradients. , Typically, an electric double layer (EDL) features negligible DO at the microscale or in microfluidic channels (>2–50 μm); however, DO becomes dominant at the nanoscale and cannot be neglected . Additional investigations are needed to clarify the feasibility and practical implementation of DO-based nanofluidic systems, in which the relationships among the temperature, material properties, and ionic strength parameters in DO-driven ion transport are of significant interest. , Most previous studies on DO use conventional nanofabrication processes with limitations in the materials governing the zeta-potentials (ζ) of the channel surfaces, throughput, dimensions, and the number of nanopores/nanochannels. , This hindered DO investigation because the governing parameters could not be varied easily. Typically, electric signals are measured along a single nanochannel, which limits the quantification accuracy because of the low transport flux.…”