Shaf is putting together some membrane reactors for testing the efficiency of enzymes at chewing up leftover organic matter (think grass clippings or crop waste) to turn it into fuels and other useful products. There is a lot of gluing involved in the prototypes. Laser-cut acrylic pieces plus a membrane form a chamber to send liquids past surface-bound enzymes. When our test solution hits an enzyme-coated membrane, it goes green– a color change we will measure with a spectrometer.
Enzymes are protein solutions with a short shelf life, so Shaf preserves the fresh solutions by flash-freezing them in liquid nitrogen. This means filling a bucket from the tank that feeds the cleanroom. Thanks to Julia we have a better container than a regular bucket.
Microdevice clinging onto 100 micron diameter fibers in a fabric
It’s the last week for most interns here, and it was a busy summer. Canisha has demonstrated that our pop-up microelectromechanical systems (MEMS) can interact with fabric fibers by curling around them. Thanks to a gentle etch process that does not damage fabrics, she was able to put nylon and polyester meshes into one of the silicon etching chambers, releasing the MEMS devices underneath. The overall goal? To transfer MEMS sensors and semiconductor circuits onto a flexible and porous support. Distortion-tolerant connectors and conformal device packaging are needed for wearable sensor systems that are built on fabrics.
These MEMS grippers are randomly aligned with the fabric, which can work as long as there are enough of them gripping. Integrating the fabric production with MEMS processing might even lead to the highly aligned system shown below. In both cases, the result is electronic circuit attached to a fabric on the underside with some connectors poking through the top of the material. This conductive path through the fabric thickness is more difficult to achieve with the thin polymer films that have previously been used with flexible electronics.
Our REU student Canisha is working on large-scale and small-scale versions of a design for an electrical contact system. “Large-scale” means assembling millimeter-scale components to a circuit board using solder paste, which she is stenciling above. In printed circuit board assembly, stenciling is followed by robotic placement of small components like resistors and diodes. “Small-scale” on this project means drawing micron-to-mm scale patterns on a photomask. One of the designs we are working on is below, but there are many more creative variants on this mask! A photomask is the starting point for photolithography, a process that prints the components side-by-side on a silicon wafer instead of assembling them individually. While we are using our photomask to make micromechanical structures, the same machines we use to pattern metal and insulating layers are used in the semiconductor industry to make chips.
Photomask pattern: each square in the grid is approximately 1.5mm x 1.5mm
This summer we have several lab projects on sensors and actuators made from soft, flexible materials.
Compliant microelectromechanical systems (MEMS)
Above: our simulation of a 2 layer plank heated at one end. This simulation connects to a couple of collaborations with other groups. Bending MEMS are being investigated for microrobots and as grippers that stick semiconductor devices such as our power-tapping diode arrays onto soft, flexible materials. Sometimes the materials are heated directly, other times we apply optically absorbent materials such as gold nanoplates to transform laser light into the heat that makes the devices change shape.
Stretchable optical fibers:
We’re working to make our stretchable optical fibers sense pressure and spatial signals. Also, making some components that will improve the connection between soft, squishy fibers and circuit boards.
Membrane-based sensors and actuators:
We’re using a thin membrane as a site for enzyme-based chemical reactor in collaboration with research groups that design enzymes. Other kinds of membranes in the lab work as pumps. One thing our group focuses on this summer is how to integrate these soft materials with the electrodes and fluidic channels that make them work in applications.
Embroidered electromagnetic actuators:
A couple of students are taking the fabric linear motor and improving its force output, combining theory and simulation to boost its mechanical power. We’re looking at some polymer-based actuator fibers too.
Last week the Embedded Systems class demoed its final projects and posted them online. The 13 projects included a spinning LED display and a plant watering system that kept track of soil moisture (ab0ve), and a “piano” that made the most of interrupts to read 8 buttons (bel0w). Projects are generally based on the Microchip 328P processor and programmed in C in the Atmel Studio environment. Yes we could use Arduino (and sometimes do) but students graduating from this class should be ready to work with whatever chip is best suited to the application. So, they spend a lot of time with the 328P datasheet learning how things work at a low level. Beyond firmware that runs on the microcontroller, there’s a mini trend toward Python and game development environments for fancy graphics on computers that connect to the microcontroller. This year’s projects included a “Boogie Ball,” a bank that added up the value of coins dropped into it, and many more. These CECS and ECE students are headed to Capstone final projects and ready to invent the future.
Enzymes are protein solutions with a short shelf life, so Shaf preserves the fresh solutions by flash-freezing them in liquid nitrogen. This means filling a bucket from the tank that feeds the cleanroom. Thanks to Julia we have a better container than a regular bucket.
