Smartphone-interfaced low-cost device for rapid microbial cell detection

Overview

This solution addresses the critical need for rapid, sensitive, and affordable detection of microbial contamination in sterile solutions. Traditional microbiological detection methods rely on time-consuming culture-based assays that can take days to deliver results. The proposed platform integrates dielectrophoresis (DEP)-based cell concentration with dynamic laser speckle imaging (DLSI) captured through a smartphone camera, enabling real-time identification of low microbial counts without the need for reagents or labels.

Beyond simple detection, the technology leverages machine learning analysis of speckle image time series to assess cell viability and even differentiate Gram-positive from Gram-negative bacteria based on differences in cell envelope and micromotion behavior. The use of low-cost, off-the-shelf optical and electronic components, combined with 3D-printed housing modules, makes the system accessible for point-of-use deployment in pharmaceutical manufacturing, clinical diagnostics, food and beverage safety, and environmental monitoring.

Technical specifications

Core technology components:

• Dielectrophoresis (DEP) trapping using PDMS-based microchambers with embedded micropillars and integrated electrodes to concentrate microbial cells from solution volumes down to low counts
• Dynamic laser speckle imaging (DLSI) using a low-cost laser diode and optical components to capture time-series speckle patterns reflecting particle kinetic behavior
• Fourier transform analysis of DLSI signals to identify and quantify bacterial particles, previously validated down to approximately 10^4 CFU/mL in macroscale cuvettes
• Machine learning classification to determine cell viability and Gram-stain category from speckle signal features tied to size, motion, and cell envelope properties
• Smartphone interface for camera-based image capture, Bluetooth-connected analyzer control, data processing, and result display
• Disposable polymer cartridge manufactured via photolithography with inlet and outlet electrodes, designed to interface directly with the sterile solution under test

Performance targets:

• Limit of detection goal of 100 CFU/mL or better, representing a 100-fold improvement over prior macroscale DLSI validation
• Reagent-free, non-destructive operation preserving cell viability for downstream analysis
• Portable form factor suitable for field or point-of-use deployment

Technology readiness level

The technology is currently at a mid-stage development level. The DLSI detection method has been validated in laboratory cuvettes achieving detection limits around 10^4 CFU/mL, and preliminary experiments with commercial electrode-integrated cuvettes have demonstrated a 10-fold improvement in sensitivity. The team is actively fabricating PDMS microchamber prototypes with embedded micropillars for DC dielectrophoresis and developing the portable analyzer and smartphone software platform. The projected one-year development timeline aims to deliver a complete prototype comprising a sensing cartridge, analyzer unit, data analysis software, and display interface. The team is seeking support for key personnel, device manufacturing, and testing to advance toward a field-ready product.