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Drake Sanborn, Amanda White, Michal Okebiorun, Adam Croteau, Jacob Tenorio, Dr. Ken Cornell, Dr. Don Plumlee, Dr. Jim Browning

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  • CAP plasma scalpel delivers plasma capable of killing bacteria found in chronic wounds
  • Scalpel used to selectively treat only stained necrotic cells
  • Prior research shows that CAP plasma can reduce bacterial colonies by 50% in 10 s and 90% after 30 s depending on substrate surface

CAP Scalpel Description

  • Scalpel fabricated from Low Temperature Co-Fired Ceramic (LTCC)
  • AC electrodes embedded under 35 µm of dielectric
  • Gas flow channel between plates for Ar
  • Discharge operates at 21kHz and 2-5 kV

Plasma Scalpel Apparatus

photo collage of diagram of apparatus, photo apparatus in lab, and screenshot of output data

Experimental Approach

Typical Plasma exposure parameters

  • Time: 2 – 5 min
  • Voltage: 2.0 – 5.0 kV
  • Frequency: 20kHz
  • Ar flow: 3 lpm
  • Dreschel Flask bubbler with DI water

Biofilms and substrates studied

  • Pseudomonas fluorescens
  • Escherichia coli 0157:H7 (ATCC 43894)
  • Glass coverslips
  • Steel coverslips

Biofilm Preparation

  • Diagram, well, LB Media and cells, steel substrateBiofilms prepared by inoculating 12-well plates with 1:100 diluted overnight stocks
  • Substrates inserted vertically into the wells, then placed in incubator
  • Coverslips removed from incubator, briefly dipped in DI water, then treated with plasma


Biofilm thickness measured using Stylus Profilometer

Typical Biofilm Heights

  • Pseudomonas fluorescens : 3 – 10 µm
  • Escherichia coli: 1 – 3 µm

Trypan Blue Staining Process

  • Tryphan blue stainBiofilm slides fully submerged in formalin to fix biofilm to the substrate
  • Excess formalin removed and trypan blue stain (0.4%) added to slides
  • Only dead cells stained with trypan blue and biofilm region is clearly visible

Image Processing

  • diagram of image processing: amber/cyam LED circuit, monochrome USB camera, and TB Stained biofilm. Photo of outputStained slides set onto the center of XY stage, below monochrome camera
  • LEDs used to provide peak reflectance and peak absorbance of trypan blue stain
  • Amber LED (λ=580 nm) provides peak absorbance
  • Cyan LED (λ=495 nm) provides peak reflectance
  • Differential taken between Cyan and Amber images to create single composite image
  • MATLAB processes image with thresholding to detect edges and display uniform biofilm region


Biofilm Staining Results

  • Most biofilm slides are able to be stained with TB
  • The slides are dark and show all of the biofilm region, making imaging easier

Plasma Scalpel Etch Results

  • plasma scalpel results, photoOne successful test that showed etching with the plasma scalpel was conducted for 5 min at 2.2kV and a proximity of 5 mm
  • Scalpel removed 1 – 2 µm of biofilm and began to expose steel substrate below

Current Issues

  • Producing consistent biofilm samples
  • Better gas flow control needed

Future Work

Begin testing on tissue and tissue-like materials

  • Pig’s ear from live pig
  • Matrigel, a gelatinous protein substrate

Create autonomous program that images a stained slide and selectively treats biofilm regions with plasma scalpel


This research is supported by the U.S. Department of Agriculture under the NIFA grant # 2018-67018-27881, by the National Institutes of Health (NIH) under Grant # 1R15EB024930-01A1, and program grants NIH/NIGMS P20GM103408 and P20GM109095. The project is also supported by the Helmsley Charitable Trust and Boise State University College of Innovation and Design as a Vertically Integrated Projects course in Plasma Medicine.

Additional Information

For questions or comments on this research, contact Drake Sanborn at