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JANUARY 2019 I FLEX007 MAGAZINE 65 out failure, or in high-reliability applications where every method of improving reliability and survivability is employed to be sure your package never fails. Another application is useful on boards that use a "pouch" manufac- turing technique, which will be discussed in our next column. Boards manufactured with a pouch construction will need a strain relief bead almost universally. Strain relief beads are placed by hand using a mechanical syringe. The adhesives vary from single- and two-part systems, but most are sensitive to heat. If baked, the adhesive will run out onto the flex area of your board. Most adhesives are then air dried, which can take up to eight hours to cure completely. A rigid-flex design with six flex arms will have 24 beads, which can take quite a bit of time to complete, and then need to air dry, adding to the lead time of your order. This article described how rigid-flex manu- facturing differs from hardboard and flex cir- cuit manufacturing on a straightforward rigid- flex construction. My next column will discuss difficult constructions, how they are accom- plished, and what are the tradeoffs in cost and yield time. FLEX007 Bob Burns is national sales and marketing manager for Printed Circuits LLC. To read past columns or contact Burns, click here. A collaboration between the University of Tokyo, Tokyo Women's Medical University, and RIKEN in Japan produced a functional sample of heart cells with a soft nanomesh sensor in direct contact with the tissue. This device could aid the study of other cells, organs, and medicines as well as pave the way for future embedded medical devices. One way or another, research on the heart is fundamen- tally important to us all. When Sunghoon Lee, a researcher in Professor Takao Someya's group at the University of Tokyo, came up with the idea for an ultrasoft electronic sensor that could monitor functioning cells, his team jumped at the chance to use this sensor to study heart cells, or cardiomyo- cytes, as they beat. For this research, collaborators from Tokyo Women's Medical University supplied a healthy culture of cardiomyocytes derived from human stem cells. The base for the cul- ture was a very soft material called fibrin gel. Lee placed the nanomesh sensor on top of the cell culture in a complex process, which involved removing and adding liquid medium at the proper times. This was important to orient the nanomesh sensor correctly. With three probes, the sensor reads volt- age present at three locations. Thanks to the multiple probes, researchers can see the propagation of signals, which result from and trigger the cells to beat. These signals are known as an action or field potential and are extremely important when assessing the effect of drugs on the heart. "Whether it's for drug research, heart monitors, or to reduce animal testing, I can't wait to see this device pro- duced and used in the field," said Lee. (Source: University of Tokyo) Engineers Create Delicate Sensor to Monitor Heart Cells With Minimal Disruption