Picoliter Drop Dispenser for Vitrified EM Specimen Preparation
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Solution Overview
Problem
Current methods for preparing EM grids in molecular microscopy lack reproducibility due to uncontrollable sample thickness and solute concentration variations, leading to suboptimal sample preservation and analysis.
Innovation Solution
A system utilizing a plunger assembly with a drop dispenser capable of picoliter-scale fluid dispensing onto independently addressable subregions of the EM grid, combined with controlled environmental conditions, to minimize blotting and ensure uniform sample thickness, allowing for precise and reproducible sample preparation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If microliter volumes of sample are applied to the EM grid using conventional blotting methods, then the sample coverage is sufficient, but the sample thickness and solute concentration become uncontrolled and non-reproducible
Solution Approach 1:
The invention changes the volume parameter from microliter scale to picoliter scale (1000-fold reduction). This parameter change enables precise control of sample thickness while maintaining adequate coverage, as the smaller volume forms a thin film that freezes uniformly without requiring blotting. The picoliter volume inherently provides the desired thickness control while preserving sufficient sample quantity for analysis.
Solution Approach 2:
Instead of applying excess sample and removing it through blotting (excessive action), the invention applies precisely the right amount of sample in picoliter volumes (partial action). This eliminates the need for blotting and the associated variability in sample thickness and solute concentration, achieving reproducible results with minimal sample volume.
2Manufacturing precision
If blotting is used to thin the sample film, then excess sample is removed, but solute concentration increases due to water evaporation and sample thickness becomes non-uniform
Solution Approach 1:
The invention performs preliminary freezing of the picoliter sample volume before evaporation can occur. By freezing the sample rapidly in the picoliter volume, the water is locked in place as ice, preventing evaporation and the associated solute concentration changes. This preliminary freezing action eliminates the harmful effects of evaporation that occur during conventional blotting.
Solution Approach 2:
The invention skips the blotting step entirely by using picoliter volumes that freeze directly without requiring manual intervention. The rapid freezing process occurs so quickly that evaporation and associated concentration changes are avoided, rushing through the critical phase before harmful effects can manifest.
3Reliability
If manual blotting is performed to control sample thickness, then some uniformity is achieved, but reproducibility between grids and within grids remains poor
Solution Approach 1:
The picoliter volume samples serve themselves by forming uniform thin films through their own small size and rapid freezing, without requiring external blotting control. The inherent properties of picoliter volumes—small size, high surface-to-volume ratio, and rapid freezing—automatically produce uniform, reproducible samples, eliminating the need for complex blotting control mechanisms.
Solution Approach 2:
The invention replaces the mechanical blotting system (forceps, blotting paper, manual manipulation) with a precision dispensing system that delivers picoliter volumes directly to the grid. This substitution eliminates the variability introduced by manual blotting mechanics and achieves superior reproducibility through precise volumetric control.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces sample volume by over 1000-fold, enabling more thorough sampling and improved analysis of precious biological samples with enhanced reproducibility and precision in molecular microscopy.
Implementation Method 1
The ultimate thickness of the sample is related to, among other things, the relative hydrophilicity of the grid surface
Implementation Method 2
vitrification (using an automated cryogenic robot) or by negative stain
Implementation Method 3
plunging the thin sample into a liquid coolant (typically liquid ethane)
Implementation Method 4
its behavior is dominated by the heat and mass transfer that result from evaporation of the aqueous sample
Data Source
AI summary
The invention provides methods and devices for preparing frozen vitrified samples for transmission electron microscopy. By reducing the volume of sample from microliter scale to picoliter scale, the requirement for blotting of excess fluid is minimized or eliminated.