Three-dimensional (3D) printing has expanded beyond the mere patterned deposition of melted solids, moving into areas requiring spatially structured soft matter—typically materials composed of polymers, colloids, surfactants, or living cells. The tunable and dynamically variable rheological properties of soft matter enable the high-resolution manufacture of soft structures. These rheological properties are leveraged in 3D printing techniques that employ sacrificial inks and sacrificial support materials, which go through reversible solid–fluid transitions under modest forces or other small perturbations. Thus, a sacrificial material can be used to shape a second material into a complex 3D structure, and then discarded. Here, we review the sacrificial materials and related methods used to print soft structures. We analyze data from the literature to establish manufacturing principles of soft matter printing, and we explore printing performance within the context of instabilities controlled by the rheology of soft matter materials.

Background. Depression and cognitive functioning have a negative impact on functional recovery after hip fracture surgery in older people, and the same has been suggested for pain and fear of falling. These variables, however, have never been studied together, nor has the timing of psychiatric assessment been taken into account.

Method. Two parallel, randomized controlled trials were undertaken aiming to prevent and treat depression after hip fracture surgery in older people. Multiple logistic regression analyses corrected for age and pre-morbid level of functioning were performed to evaluate the effect of depressive symptoms (15-item Geriatric Depression Scale, GDS), pain (Wong–Baker pain scale), cognitive functioning (Mini-mental State Examination, MMSE) and fear of falling (Modified Falls Efficacy Scale, MFES) within 2 weeks after surgery and 6 weeks later on functional recovery at 6 months. Main outcome measures were performance-based measures (up-and-go test, gait test, functional reach) and the self-report Sickness Impact Profile (SIP) questionnaire to assess the impact of the hip fracture on activities of daily living (ADL).

Results. Two hundred and ninety-one patients participated and outcome measures for 187 (64%) patients were available at 6 months. All mental health variables interfered with functional recovery. However, in the final multivariate model, cognitive functioning and fear of falling assessed 6 weeks after surgery consistently predicted functional recovery, whereas pain and depressive symptoms were no longer significant.

Conclusion. Fear of falling and cognitive functioning may be more important than pain and depression to predict functional recovery after hip fracture surgery. Rehabilitation strategies should take this into account.