Hydrogels consist of a cross-linked polymer matrix imbibed with a solvent such as water at volume fractions that can exceed 90%. They are important in many scientific and engineering applications due to their tunable physiochemical properties, biocompatibility, and ultralow friction. Their multiphase structure leads to a complex interfacial rheology, yet a detailed, microscopic understanding of hydrogel friction is still emerging. Using a custom-built tribometer, here we identify three distinct regimes of frictional behavior for polyacrylic acid (PAA), polyacrylamide (PAAm), and agarose hydrogel spheres on smooth surfaces. We find that at low velocities, friction is controlled by hydrodynamic flow through the porous hydrogel network and is inversely proportional to the characteristic pore size. At high velocities, a mesoscopic, lubricating liquid film forms between the gel and surface that obeys elastohydrodynamic theory. Between these regimes, the frictional force decreases by an order of magnitude and displays slow relaxation over several minutes. Our results can be interpreted as an interfacial shear thinning of the polymers with an increasing relaxation time due to the confinement of entanglements. This transition can be tuned by varying the solvent salt concentration, solvent viscosity, and sliding geometry at the interface.

Objective: TeleDREAMS, a distance learning version of the Developing a Research Participation Enhancement and Advocacy Training Program for Diverse Seniors (DREAMS) program, provides remote clinical research process and advocacy education to older adults with Parkinson's disease (PD) and their care partners. Method: Participants engaged in remote learning, reading eight weekly clinical research process and advocacy education modules. They also had weekly half hour phone discussions with staff about each module. Participants (PD: n = 28, care partner: n = 15) were tested on health literacy, quality of life, depression, research involvement, and advocacy measures. Results: People with PD improved on health literacy postintervention. PD participants who participated with care partners improved more on health literacy than those without care partners. PD participants' attrition rates were lower for PD participants in TeleDREAMS than those of the similar, in-person program DREAMS program studied before TeleDREAMS. Most participants reported research involvement and patient advocacy for older adults with PD 6 to 9 months postprogram. Conclusions: TeleDREAMS may improve health literacy in participants with Parkinson's and their care partners. If increased advocacy and health and research literacy translates to increased research involvement, then TeleDREAMS could be an important strategy for researchers interested in increasing participation.