Realizing new designs of multiplexed electrode chips by 3-D printed masks

3D-printed shadow masks for micro-patterned electrodes

Microfabrication is critical to the advancement of lab-on-chip devices by enabling the creation of high-precision, complex electrode structures. Traditional photolithography, commonly used to fabricate micro-patterned electrodes, involves complex and multi-step processes that can be costly and time-consuming. In this research, we present a method using 3D-printed shadow masks for electrode fabrication, offering a simpler, cost-effective alternative to traditional methods. Specifically, by leveraging a fused deposition modeling 3D printer, we demonstrate that 3D-printed shadow masks streamline rapid prototyping of micro-patterned electrodes with a range of designs, from simple lines to complex patterns. To assess the lab-on-chip functionality of the electrodes fabricated from 3D-printed shadow masks, we investigate electric field-driven assembly of microparticles in the electrodes. The micro-patterned designs of the electrodes remotely guide the assembly patterns, resulting in the formation of well-defined, multiple chains and anisotropic structures. These results suggest that 3D-printed shadow masks not only simplify the fabrication process, but also maintain the precision required for advanced lab-on-chip applications. The proposed method could pave the way for more accessible and scalable manufacturing of the complex micro-patterned electrodes.

Single-Response Duplexing of Electrochemical Label-Free Biosensor from the Same Tag

Multiplexing is a valuable strategy to boost throughput and improve clinical accuracy. Exploiting the vertical, meshed design of reproducible and low-cost ultra-dense electrochemical chips, the unprecedented single-response multiplexing of typical label-free biosensors is reported. Using a cheap, handheld one-channel workstation and a single redox probe, that is, ferro/ferricyanide, the recognition events taking place on two spatially resolved locations of the same working electrode can be tracked along a single voltammetry scan by collecting the electrochemical signatures of the probe in relation to different quasi-reference electrodes, Au (0 V) and Ag/AgCl ink (+0.2 V). This spatial isolation prevents crosstalk between the redox tags and interferences over functionalization and binding steps, representing an advantage over the existing non-spatially resolved single-response multiplex strategies. As proof of concept, peptide-tethered immunosensors are demonstrated to provide the duplex detection of COVID-19 antibodies, thereby doubling the throughput while achieving 100% accuracy in serum samples. The approach is envisioned to enable broad applications in high-throughput and multi-analyte platforms, as it can be tailored to other biosensing devices and formats.

Phospholipid-functionalized gold electrode for cellular membrane interface studies - interactions between DMPC bilayer and human cystatin C

This work describes the electrochemical studies on the interactions between V57G mutant of human cystatin C (hCC V57G) and membrane bilayer immobilized on the surface of a gold electrode. The electrode was modified with 6-mercaptohexan-1-ol (MCH) and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC). DMPC was used as a membrane mimetic for monitoring electrochemical changes resulting from the interactions between the functionalized electrode surface and human cystatin C. The interactions between the modified electrode and hCC V57G were investigated by cyclic voltammetry and electrochemical impedance spectroscopy in a phosphate buffered saline (PBS) containing Fe(CN)63-/4- as a redox probe. The electrochemical measurements confirm that fabricated electrode is sensitive to hCC V57G at the concentration of 1 × 10-14 M. The incubation studies carried out at higher concentrations resulted in insignificant changes observed in cyclic voltammetry and electrochemical impedance spectroscopy measurements. The calculated values of surface coverage θR confirm that the electrode is equally covered at higher concentrations of hCC V57G. Measurements of wettability and surface free energy made it possible to determine the influence of individual structural elements of the modified gold electrode on its properties, and thus allowed to understand the nature of the interactions. Contact angle values confirmed the results obtained during electrochemical measurements, indicating the sensitivity of the electrode towards hCC V57G at the concentration of 1 × 10-14 M. In addition, the XPS spectra confirmed the successful anchoring of hCC V57G to the DMPC-functionalized surface.

Metallization of Recycled Glass Fiber-Reinforced Polymers Processed by UV-Assisted 3D Printing

An ever-growing amount of composite waste will be generated in the upcoming years. New circular strategies based on 3D printing technologies are emerging as potential solutions although 3D-printed products made of recycled composites may require post-processing. Metallization represents a viable way to foster their exploitation for new applications. This paper shows the use of physical vapor deposition sputtering for the metallization of recycled glass fiber-reinforced polymers processed by UV-assisted 3D printing. Different batches of 3D-printed samples were produced, post-processed, and coated with a chromium metallization layer to compare the results before and after the metallization process and to evaluate the quality of the finishing from a qualitative and quantitative point of view. The analysis was conducted by measuring the surface gloss and roughness, analyzing the coating morphology and thickness through the Scanning Electron Microscopy (SEM) micrographs of the cross-sections, and assessing its adhesion with cross-cut tests. The metallization was successfully performed on the different 3D-printed samples, achieving a good homogeneity of the coating surface. Despite the influence of the staircase effect, these results may foster the investigation of new fields of application, as well as the use of different polymer-based composites from end-of-life products, i.e., carbon fiber-reinforced polymers.

Investigating electrochemical deposition of gold on commercial off-the-shelf 3-D printing materials towards developing sensing applications†

The COVID-19 pandemic highlighted the inaccessibility of quick and affordable clinical diagnostics. This led to increased interest in creating low-cost portable electrochemical (EC) devices for environmental monitoring and clinical diagnostics. One important perspective is to develop new fabrication methods for functional and low-cost electrode chips. Techniques, such as electron beam and photolithography, allow precise and high-resolution electrode fabrication; however, they are costly and can be time-consuming. More recently, fused deposition modeling three-dimensional (3-D) printing is being used as an alternative fabrication technique due to the low-cost of the printer and rapid prototyping capability. In this study, we explore enhancing the conductivity of 3-D printed working electrodes with EC gold deposition. Two commercial conductive filament brands were used and investigated to fabricate electrode chips. Furthermore, strategies to apply epoxy glue and conductive silver paint were investigated to control the electrode surface area and ensure good electrical connection. This device enables detection at drinking water concentration thresholds. The practical application of the fabricated electrodes is demonstrated by detecting Cu²⁺ using anodic stripping voltammetry.

Customized electrodes were made with 3-D printing and gold electrochemical reduction towards analytical applications.