Maximizing the speed and efficiency at which single cells can be liberated from tissues would dramatically advance cell-based diagnostics and therapies. Conventional methods involve numerous manual processing steps and long enzymatic digestion times, yet are still inefficient. In previous work, we developed a microfluidic device with a network of branching channels to improve the dissociation of cell aggregates into single cells. However, this device was not tested on tissue specimens, and further development was limited by high cost and low feature resolution. In this work, we utilized a single layer, laser micro-machined polyimide film as a rapid prototyping tool to optimize the design of our microfluidic channels to maximize dissociation efficiency. This resulted in a new design with smaller dimensions and a shark fin geometry, which increased recovery of single cells from cancer cell aggregates. We then tested device performance on mouse kidney tissue, and found that optimal results were obtained using two microfluidic devices in series, the larger original design followed by the new shark fin design as a final polishing step. We envision our microfluidic dissociation devices being used in research and clinical settings to generate single cells from various tissue specimens for diagnostic and therapeutic applications.

The objective of this research was to assess the performance of an embedded sensing system designed to measure the distance between a prosthetic socket wall and residual limb. Low-profile inductive sensors were laminated into prosthetic sockets and flexible ferromagnetic targets were created from elastomeric liners with embedded iron particles for four participants with transtibial amputation. Using insights from sensor performance testing, a novel calibration procedure was developed to quickly and accurately calibrate the multiple embedded sensors. The sensing system was evaluated through laboratory tests in which participants wore sock combinations with three distinct thicknesses and conducted a series of activities including standing, walking, and sitting. When a thicker sock was worn, the limb typically moved further away from the socket and peak-to-peak displacements decreased. However, sensors did not measure equivalent distances or displacements for a given sock combination, which provided information regarding the fit of the socket and how a sock change intervention influenced socket fit. Monitoring of limb–socket displacements may serve as a valuable tool for researchers and clinicians to quantitatively assess socket fit.

A prosthesis user may also make more frequent sock adjustments if fit is not right, or he/she may doff the prosthesis more often or longer to allow fluid volume recovery and offset daily volume loss. How prosthesis users feel about their socket fit and how they accommodate volume changes is important information for practitioners treating patients with limb loss. Practitioners traditionally use self-report information during clinical visits to educate the patient about accommodation methods, make socket adjustments, and determine when a new prosthesis is needed. However, information collected by self-report may be affected by issues such as recall, perception, and social desirability. 3.4 As a result, the practitioner may have to try several different adjustments in order to correct comfort and fit problems. This iterative approach to solving socket fit issues can be time consuming, costly, and potentially detrimental to the prosthesis user's residual limb health. Electronic sensors have been developed to monitor prosthesis use and provide practitioners and patients with an objective record of wear. 5,6 Proximity sensors mounted to the socket brim or embedded within the socket wall have been used previously to detect the presence of the residual limb within the socket. The sensors produced reliable data but consumed too much power to be practical for long-term field use. The purpose of this study was to extend from prior work and develop a portable sensor that measured when the prostheses was donned and doffed and that was capable of long-term (i.e., 2-wk) monitoring. We tested hypotheses that there would be no significant differences between self-report and electronically recorded start of day, end of day, and day durations, and that weekly prosthesis use would differ from weekend prosthesis use among people with transtibial amputation. We also characterized the frequency of socket releases and their durations, as well as doff durations for sock changes using the electronic sensor. From self-report data, we characterized start-of-day sock thicknesses and frequency of sock changes.

Introduction Wearable limb–socket displacement sensors may help patients and prosthetists identify a deteriorating socket fit and justify the need for repair or replacement. Methods A novel sensor using an inductive sensing modality was developed to detect limb-to-socket distances. Key detection elements were a coil antenna placed in the socket wall and a magnetic composite sheath worn over the outside of the prosthesis user's elastomeric liner. The sheath was a nylon or cotton prosthetic stocking coated with a polyurethane composite. The polyurethane composite contained embedded iron particles (75 wt%). Results Brushing γ-glycidoxypropyltriethoxysilane onto the sheath fabric, coating it first with unfilled polyurethane and then iron-filled polyurethane, enhanced bonding between the sheath and the composite and overcame mechanical degradation problems. A γ-glycidoxypropyltriethoxysilane-rich fumed silica layer applied to the outside of the sheath reduced friction and improved durability. Field testing demonstrated less than a 3% signal degradation from four weeks of field use. Conclusions The developed wearable displacement sensor meets durability and performance needs, and is ready for large-scale clinical testing.