Wednesday, January 22, 2020

Stretchy bioelectronics and ptychographic imaging - two fun talks

One of the great things about a good university is the variety of excellent talks that you can see. 

Yesterday we had our annual Chapman Lecture on Nanotechnology, in honor of Rice alum Richard Chapman, who turned down a first-round draft selection to the Detroit Lions to pursue a physics PhD and a career in engineering.  This year's speaker was Zhenan Bao from Stanford, whom I know from back in my Bell Labs postdoc days.  She spoke about her group's remarkable work on artificial skin:  biocompatible, ultraflexible electronics including active matrices of touch sensors, transistors, etc.  Here are a few representative papers that give you some idea of the kind of work that goes into this: Engineering semiconducting polymers to have robust elastic properties while retaining high charge mobilities; a way of combining conducting polymers (PEDOT) with hydrogels so that you can pattern them and then hydrate to produce super-soft devices; a full-on demonstration of artificial skin for sensing applications.  Very impressive stuff. 

Today, we had a colloquium by Gabe Aeppli of ETH and the Paul Scherrer Institute, talking about x-ray ptychographic imaging.  Ptychography is a simple enough idea.  Use a coherent source of radiation to illuminate some sample at some spot, and with a large-area detector, measure the diffraction pattern.  Now scan the spot over the sample (including perhaps rotating the sample) and record all those diffraction patterns as well.  With the right approach, you can combine all of those diffraction patterns and invert to get the spatial distribution of the scatterers (that is, the matter in the sample).  Sounds reasonable, but these folks have taken it to the next level (pdf here).   The video I'm embedding here is the old result from 2017.  The 2019 paper I linked here is even more impressive, able to image, nondestructively, in 3D, individual circuit elements within a commercial integrated circuit at nanoscale resolution.  It's clear that a long-term goal is to be able to image, non-destructively, the connectome of brains. 


Anonymous said...

One challenge in ptychography is dealing with unknown composition, as the technique doesn't differentiate that well by chemical composition (except very grossly by atomic number). I think this is a major challenge for young researchers to delve into.

Don Monroe said...

Cool. Good for Zhenan. Gabe also spent early years of his career at Bell Labs.

Since you mention the connectome, it turns out that HHMI's Janelia Farms just announced "the most complete" version for the fruit fly, Drosophila melanogaster. It's not easy: I stumbled across this page listing almost 40 "connectome annotators" at Janelia Farms.