Steering and refocusing are different mechanical problems, and that is why they usually get different parts. Sweeping a beam sideways wants rigid-body motion, a plate that tips cleanly and comes back. Moving the focal plane wants controlled deformation, a surface that changes curvature without losing its figure. The Penn State device gets both out of one piece of aluminum nitride: structures around the mirror tip it in two directions, while a separate piezoelectric layer on the mirror itself pulls the reflective surface between flat and shallow bowl [5][4]. Take that second job onto the same membrane and the second optical element leaves the path [13].
The speed figure is worth pausing on. The team measured the focus changing within millionths of a second [7]. Neurons, the thing Shillingburg most wants to point this at, become active in thousandths of a second [9]. One millisecond divided by one microsecond is a factor of about a thousand [16], which says the mirror is unlikely to be the slow axis in a volumetric recording loop. What sets that pace instead is an open question, since the account describes no imaging demonstration and gives no frame rates for a complete system [17].
There is also the 63 millimeters. Changing the drive voltage moved the focus of a laser-scanned pattern by that distance [8], which is a large excursion on an optical bench and an ambiguous one for a microscope. Missing from this account is the axial range you would keep behind an objective, and how the spot holds up at full curvature: no tilt angle, no aperture, no optical quality figure appears here, though the paper in Microsystems & Nanoengineering may carry them [2][17]. Depth range inside scattering tissue is a system property, and a free-space number is not a substitute for measuring it.
The fabrication side is the least speculative part. MEMS devices are built on chips using many of the same methods used to make computer chips [14], so a piezoelectric tilt-and-flex mirror is not an exotic process, and the co-author list runs through Penn State's Materials Research Institute, with Daniel Lopez now chairing physics at Arizona State [3]. What a head-mounted instrument would still need is drive electronics for a piezoelectric plate, and this account does not spec the voltages [19].
So: a good component result, with the system question open. The mechanism is credible and the mechanical argument for putting both functions on one membrane is the strongest part of it, per Shillingburg's own framing that single-device 3D control buys size and weight in the whole optical system [10]. What this leaves unanswered is whether a miniature scope built around it images a moving animal's cortex any better than the two-element design it would replace. Settling that calls for a microscope, not just a mirror.
