Multiscale Physics in Energy Systems Group Ilenia Battiato

Laboratory

The Multiscale Physics in Energy Systems wet laboratory is equipped to perform microfluidic experiments and observe dynamically passive and reactive transport processes in both synthetic and geologic porous media. We use microfluid experiments (i) to develop tools that allow us to span a variety of physical temporal and spatial scales, (ii) to validate models and theories at different scales, and (iii) to investigate and characterize complex dynamic coupling between advection, reaction, gas generation and diffusion in heterogeneous reactive geologic media. Our ultimate objective is to use experiments to guide the development of predictive models for multiscale multiphysics systems with realistic complexities. Our current experimental capabilities include microscopy and microfabrication (performed at the Stanford Nanofabrication Facility, SNF).

1. Microscopy

Inverted Microscope: The inverted microscope in the Multiscale Physics in Energy Systems Group allows us to directly visualize in real-time the physical (e.g., flow and transport in porous media) and chemical (e.g., mineral dissolution) phenomena that occur inside microfluidic devices and record the images with high spatial and temporal resolution.

Figure 1: Nikon Ti-E inverted microscope

Instrument Capability:

  • Equipped with ×2, ×4, ×10, and ×20 objectives covering 6 x 6 mm to 0.6 by 0.6 mm field of view
  • Connected to Hamamatsu high-speed CMOS camera capable of recording ~10 high-resolution images per second
  • Capable of measuring intensity variations at a specified location
    • The measured intensity maps can be translated into breakthrough curves from tracer experiments

Figure 2: Imaging of CO2 gas generation during carbonate dissolution of a Marcellus sample. [Image credit: Bowen Ling]

Scanning Electron Microscopy: We use the SEM/EDS located in Green Earth Sciences to acquire static images of rock samples before and after the reaction. Such images allow us to visualize the changes in rock surface topology and mineralogy due to dissolution reactions.

Instrument Capability:

  • JEOL JSM-IT500HR scanning electron microscope (located in Green Earth Sciences Building)
  • Equipped with backscattered electron (BSE) and secondary electron (SE) detectors
  • Equipped with Thermo Scientific energy-dispersive spectrometer (EDS)

Figure 3: (A) Sample-embedded microfluidic cell construction (B) Compositional ternary plot of the geologic samples analyzed. (C) SEM-EDS pre-reaction characterization of samples with increasing carbonate content (left to right) [Figure Adapted from Ling et al. PNAS (2022)].

2. Microfabrication

The microfluidic devices used in the research group are fabricated in-house using the facilities at Stanford Nanofabrication Facility (SNF). Microfabrication is a multi-step process that starts with either building up micro-scale features or selectively engraving patterns on a silicon wafer at multiple depths (Figure 3). The following is a list of main equipment used in our research group to fabricate and characterize microfluidic devices.

Photolithography

  1. Automatic SVG Resist Coater
  2. Karl Suss MA-6 Contact Aligner
  3. Heidelberg MLA 150
  4. Automatic SVG Resist Developer


Etching

  1. STS Deep Reactive Ion Etcher
  2. Plasma Therm Versaline Deep Silicon Etcher


Bonding

  1. Plasmaetch PE-50
  2. Electronic Vision 501 Bonder


Surface Analysis

  1. Sensofar S-neox
  2. Alphastep 500 Profilometer

Figure 4. SEM images of microfluidic features etched into a silicon surface via the Bosch process [Image credit: Jun Hwang]