Polymer-based Neural Microprobes
The activities of the brain and nervous system are conveyed through electrochemical signals transmitted between cells. Tiny electrical sensors implanted into the brain (or peripheral nerves) can detect, and even stimulate this neural activity, enabling the study and manipulation of individual neural circuits. These sensors, called ‘neural probes’, are manufactured with microscopic dimensions, both to avoid injury and to render them sensitive to the electrical signals of individual neurons. Developing a safe and reliable neural probe has proven very difficult; probes can damage the soft neural tissue, triggering the body’s immune response and inducing scarring, inflammation, and even nerve damage.
The aim of this project is to develop a suite of polymer-based microsensors to serve as soft, flexible, and biocompatible neural probes and peripheral nerve interfaces. By adapting the microfabrication techniques used to develop integrated circuitry, we can create microscale electronics on flexible organic polymers better suited for biomedical implantation than conventional electronics materials (e.g. metal, glass, semiconductors).
Relevant Publications
The aim of this project is to develop a suite of polymer-based microsensors to serve as soft, flexible, and biocompatible neural probes and peripheral nerve interfaces. By adapting the microfabrication techniques used to develop integrated circuitry, we can create microscale electronics on flexible organic polymers better suited for biomedical implantation than conventional electronics materials (e.g. metal, glass, semiconductors).
Relevant Publications
Nanofabrication on Flexible Substrates
Today, microelectronic devices can be fabricated from flexible materials, like thin polymers or paper, for the creation of flexible displays, sensors, and biomedical devices. However, the micrometer-scale pattern resolution typical for flexible devices cannot compare to the sub-micron resolutions achievable in the semiconductor manufacturing industry. Polymers have limited tolerance for the high temperatures, intense radiation, and harsh chemicals used in standard micro- and nano-fabrication processing.
The aim of this project is to develop high-resolution lithography techniques compatible with flexible substrates. The principal application is the development of polymer-based, biomedical sensors with high-feature density and low-feature size. By adapting techniques such as electron-beam lithography to organic polymers, we have successfully produced simple structures including wire traces, planar resistors and thin-film capacitors with sub=micron dimensions in thin-film Parylene C devices. This technique can be used to produce polymer-based neural probes with large numbers of recording sites, featuring electrical traces with sub-micron pitch and width, and nano-textured electrodes.
Relevant Publications
The aim of this project is to develop high-resolution lithography techniques compatible with flexible substrates. The principal application is the development of polymer-based, biomedical sensors with high-feature density and low-feature size. By adapting techniques such as electron-beam lithography to organic polymers, we have successfully produced simple structures including wire traces, planar resistors and thin-film capacitors with sub=micron dimensions in thin-film Parylene C devices. This technique can be used to produce polymer-based neural probes with large numbers of recording sites, featuring electrical traces with sub-micron pitch and width, and nano-textured electrodes.
Relevant Publications
Temporary 'Smart Tattoo'
'Smart Tattoos' are thin, flexible, polymer-based electronic devices that can be safely and unobtrusively bonded to the skin. Smart Tattoos are being developed for applications such as biomedical and health/wellness monitoring, wearable electronic interfaces, and radio-frequency identification (RFID). Major challenges include designing components that do not break during the natural motion of the skin, and providing wireless power and communication to and from the device.
I am working to develop a series of simple, effective components for Smart Tattoos using lithographic patterning on Parylene C.
As a demonstration, I have created a wearable Metro TAP Tattoo, compatible with the Los Angeles Metro subway system.
I am working to develop a series of simple, effective components for Smart Tattoos using lithographic patterning on Parylene C.
As a demonstration, I have created a wearable Metro TAP Tattoo, compatible with the Los Angeles Metro subway system.
MEMS Sensors for Environmental Monitoring
A small volume of air may contain dozens to hundreds of volatile organic compounds present in low concentrations. While many of these species may be benign, others may be hazardous pollutants or industrial byproducts. Real-time monitoring of our environmental or occupational exposure is challenging; the analytical equipment necessary to detect trace levels of gas-phase chemicals are typically expensive and bulky.
The aim of this project is to develop miniature sensors and analytical systems capable of rapidly detecting these airborne species with high specificity and high sensitivity. Complex laboratory equipment, such as a gas chromatographic analyzer, can be rendered in miniature by replacing traditional components with Micro-ElectroMechanical Systems (MEMS). Powerful yet tiny sensors can be produced from a combination of microfluidics, microelectronics, and nanomaterials, able to detect picograms of gas-phase chemicals. Examples of experimental sensors developed as part of this effort include: gold-nanoparticle chemiresistive sensors; tin-oxide nanowire sensors; micro-optofluidic ring resonators.
Relevant Publications
The aim of this project is to develop miniature sensors and analytical systems capable of rapidly detecting these airborne species with high specificity and high sensitivity. Complex laboratory equipment, such as a gas chromatographic analyzer, can be rendered in miniature by replacing traditional components with Micro-ElectroMechanical Systems (MEMS). Powerful yet tiny sensors can be produced from a combination of microfluidics, microelectronics, and nanomaterials, able to detect picograms of gas-phase chemicals. Examples of experimental sensors developed as part of this effort include: gold-nanoparticle chemiresistive sensors; tin-oxide nanowire sensors; micro-optofluidic ring resonators.
Relevant Publications
- Vapor discrimination with single-and multitransducer arrays of nanoparticle-coated chemiresistors and resonators
- Organic vapor discrimination with chemiresistor arrays of temperature modulated tin-oxide nanowires and thiolate-monolayer-protected gold nanoparticles
- A microfabricated optofluidic ring resonator for sensitive, high-speed detection of volatile organic compounds
Optofluidic Resonators for Chemical Sensing
An optical resonator is a structure which can confine light of a certain wavelength. One example is a ‘ring resonator’, a small, thin ring of glass or silicon we can use to trap a circulating mode of light. These structures can be used to create powerful chemical and biological sensors; the presence of just a few molecules on the surface of the resonator can perturb the optical resonance.
The aim of this project is to create an optofluidic resonator: an optical resonator that seamlessly incorporates a microfluidic pathway for rapid and sensitive detection of gas-phase analytes. The three-dimensional resonator is made from a thin (~1 micrometer thick) silicon dioxide shell, coated internally with film of polymer or nanoparticles. A mode of light circles around the diameter of the shell, while a stream of gas passes through the interior. When analytes are present in the stream, they sorb into the film, shifting the resonance frequency. The microscale optofluidic resonator developed here has a pictogram detection limit, and has been used for single and two-dimensional microscale gas chromatography.
Relevant Publications
The aim of this project is to create an optofluidic resonator: an optical resonator that seamlessly incorporates a microfluidic pathway for rapid and sensitive detection of gas-phase analytes. The three-dimensional resonator is made from a thin (~1 micrometer thick) silicon dioxide shell, coated internally with film of polymer or nanoparticles. A mode of light circles around the diameter of the shell, while a stream of gas passes through the interior. When analytes are present in the stream, they sorb into the film, shifting the resonance frequency. The microscale optofluidic resonator developed here has a pictogram detection limit, and has been used for single and two-dimensional microscale gas chromatography.
Relevant Publications
- Microfabricated optofluidic ring resonator structures
- A microfabricated optofluidic ring resonator for sensitive, high-speed detection of volatile organic compounds
- Polymer-coated micro-optofluidic ring resonator detector for a comprehensive two-dimensional gas chromatographic microsystem: μGC× μGC–μOFRR