Nanotextured superhydrophobic electrodes enable detection of attomolar-scale DNA concentration within a droplet by non-faradaic impedance spectroscopy.
Aida Ebrahimi,Piyush Dak,Eric Salm,Susmita Dash,Suresh V. Garimella,Rashid Bashir,Muhammad A. Alam +6 more
TLDR
This work has developed a fast, low cost, non-faradaic impedance sensing method for detection of synthetic DNA molecules in DI water at attomolar levels by beating the diffusion limit through evaporation of a micro-liter droplet of DNA on a nanotextured superhydrophobic electrode array.Abstract:
Label-free, rapid detection of biomolecules in microliter volumes of highly diluted solutions (sub-femtomolar) is of essential importance for numerous applications in medical diagnostics, food safety, and chem-bio sensing for homeland security. At ultra-low concentrations, regardless of the sensitivity of the detection approach, the sensor response time is limited by physical diffusion of molecules towards the sensor surface. We have developed a fast, low cost, non-faradaic impedance sensing method for detection of synthetic DNA molecules in DI water at attomolar levels by beating the diffusion limit through evaporation of a micro-liter droplet of DNA on a nanotextured superhydrophobic electrode array. Continuous monitoring of the impedance of individual droplets as a function of evaporation time is exploited to dramatically improve the sensitivity and robustness of detection. Formation of the nanostructures on the electrode surface not only increases the surface hydrophobicity, but also allows robust pinning of the droplet contact area to the sensor surface. These two features are critical for performing highly stable impedance measurements as the droplet evaporates. Using this scheme, the detection limit of conventional non-faradaic methods is improved by five orders of magnitude. The proposed platform represents a step-forward towards realization of ultra-sensitive lab-on-chip biomolecule detectors for real time point-of-care application. Further works are however needed to ultimately realize the full potential of the proposed approach to appraise biological samples in complex buffer solutions rather than in DI water.read more
Citations
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Recent advances in the potential applications of bioinspired superhydrophobic materials
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Assessment of water droplet evaporation mechanisms on hydrophobic and superhydrophobic substrates.
TL;DR: The large deviations between past analytical models and the experimental data are reconciled with the comprehensive model developed here and the numerically calculated evaporation rates agree with experimental results to within 2% for superhydrophobic substrates and 3% for hydrophilic substrates.
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Sessile droplets for chemical and biological assays
TL;DR: The physics of droplets are introduced, and the different types of chemical and biological assays that have been implemented in sessile droplets, including analyte concentration, particle separation and sorting, cell-based assays, and nucleic acid amplification are focused on.
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Tactic, reactive, and functional droplets outside of equilibrium
TL;DR: As practical applications of droplets also begin to appear (e.g., in single-cell diagnostics, new methods of electricity generation, optofluidics, or sensors), it appears timely to review and systematize progress.
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Analysis and feasibility of an evaporative cooling system with diffusion-based sessile droplet evaporation for cooling microprocessors
TL;DR: In this paper, a feasibility analysis is undertaken to assess the capability of an evaporative cooling system using diffusion-based evaporation of sessile water droplets to provide sufficient cooling of microprocessors within the space requirements of the current heat sinks.
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