Research Areas

My research interests are primarily focused on bringing novel electronic platforms to applications in chemistry, biology, and medicine. This work has spanned a variety of interdisciplinary fields, including CMOS integrated circuits, embedded systems, microfabrication, immunochemistry, and chemical sensing. Previous and ongoing research interests include:


CMOS-enabled Sensor Platforms

Traditional chemical and biological assays rely on secondary reporters for detection of binding events, as with the use of fluorescent reporters for microarrays or colorimetric enzyme labels for immunoassays. These techniques add cost and complexity to assays, provide only end-point interrogation, and often limit multiplexed detection. A move towards real-time, label-free assays provides many advantages.

One approach is to use micron-scale piezoelectric resonant sensors, which have been fabricated directly atop custom CMOS integrated circuit substrates. This enables a dense array of label-free sensors with a simple, digital interface. This work was conducted primarily in the Bioelectronic Systems Lab at Columbia University. Read more...

Radiation Biodosimetry
   
 
Current strategies for minimally-invasive biodosimetry rely on the establishment of centralized testing centers with high-throughput assay processing. Patient samples must be collected and transported to a testing center, with transportation networks often compromised alongside a nuclear accident. A point-of-care biodosimetry platform would allow on-site dose quantitation, facilitating appropriate medical triage and emergency management. This is a critical and unmet need for the preparation and response to a nuclear release event.

I currently lead an effort to employ the FBAR-CMOS sensor array for point-of-care radiation biodosimetry. This work is conducted at the bioelectronic company Bialanx and is supported by a National Science Foundation Small Business Innovation Research (SBIR) Phase I grant. Read more...
https://sites.google.com/site/matthewjohnston/r-d/radiation-biodosimetry

Accessible Real-Time PCR
            
State of the art nucleic acid detection is often performed using a quantitative polymerase chain reaction (qPCR) assay, in which DNA amplification is combined with fluorescent labeling to enable real-time interrogation of specific DNA amplification. Historically, this requires a large, complex, and expensive piece of laboratory equipment.

I was co-founder and Manager of Research at Helixis, a Caltech spin-out that successfully developed a novel thermal transfer method for qPCR. This enabled high-speed, low-cost thermal cyclers. Helixis was acquired by Illumina in 2010, and this product is now available as the Eco Real-Time PCR instrument. We applied a related idea to enable ultra-fast PCR reactions, with full amplification in under two minutes. Read more...
    
Accessible Real-Time PCR


Novel structures and thermal control in microfluidics
            
Microfludics have become an established, critical component of lab-on-chip and micro-total-analysis systems. These techniques have been employed both academically and industrially for control and routing of small fluid volumes.

I have worked on a variety of novel structures and systems for microfluidic networks.
This includes the development microfludic check valves in conventional replication molding, as well as early work in 3D-printed microfluidic molds using wax-based rapid prototyping. I also worked on thermal control at the micron-scale, using embedded Peltier devices for solid-state heating and cooling of microfluidic channels and chambers. Read more...
   Microfluidic structures and methods